Today's Message Index:
----------------------
1. 05:49 AM - Alternator Killers? Re: Ongoing soap opera (Ed Anderson)
2. 06:21 AM - OVP Resolution (Giffen A Marr)
3. 06:28 AM - Re: Alternator characteristics (Gary Casey)
4. 06:56 AM - Re: Ongoing soap opera (Dj Merrill)
5. 07:02 AM - Re: Points for discussion OVP//more (Jerry Isler)
6. 07:13 AM - Re: Alternator characteristics (Robert L. Nuckolls, III)
7. 07:34 AM - Re: Re: (Paul Messinger)
8. 07:34 AM - Re: Alternator characteristics (Paul Messinger)
9. 07:47 AM - Re: Ongoing soap opera (Robert L. Nuckolls, III)
10. 07:58 AM - Re: Ongoing soap opera (Robert L. Nuckolls, III)
11. 08:15 AM - Re: Alternator characteristics (Robert L. Nuckolls, III)
12. 09:54 AM - Auto Pilot (rd2@evenlink.com)
13. 10:50 AM - Re: AeroElectric-List Digest: 33 Msgs - 03/21/05 (Speedy11@aol.com)
14. 11:01 AM - Re: Ongoing Soap Opera (Speedy11@aol.com)
15. 11:07 AM - Re: Auto Pilot (Stein Bruch)
16. 11:40 AM - Re: Re: 20% better efficiency ??? (Paul Messinger)
17. 11:40 AM - Diodes across relay coils (Paul Messinger)
18. 11:40 AM - Re: Alternator characteristics (Paul Messinger)
19. 11:40 AM - Re: Re: Alternator characteristics (Paul Messinger)
20. 11:40 AM - Circuit breaker ratings for OVP (Paul Messinger)
21. 11:51 AM - Re: Alternator characteristics (Paul Messinger)
22. 12:03 PM - Re: Circuit breaker ratings for OVP (Matt Prather)
23. 01:52 PM - Re: Auto Pilot (rd2@evenlink.com)
24. 02:12 PM - Re: DC Power Systems Dynamics - Breakers (Robert L. Nuckolls, III)
25. 02:42 PM - Grandsons Aircraft Ride at Pensacola on March 24. (Eric Ruttan)
26. 02:57 PM - Re: Circuit breaker ratings for OVP (Kingsley Hurst)
27. 03:05 PM - Extra Voltage! ()
28. 05:13 PM - Re: Re: DC Power Systems Dynamics - Breakers (Paul Messinger)
29. 05:19 PM - Re: Circuit breaker ratings for OVP (Robert L. Nuckolls, III)
30. 06:04 PM - Re: Re: Ongoing Soap Opera (Robert L. Nuckolls, III)
31. 06:39 PM - Re: Circuit breaker ratings for OVP (Andrew Rowley)
32. 06:39 PM - Re: Circuit breaker ratings for OVP (Andrew Rowley)
33. 07:52 PM - Re: Circuit breaker ratings for OVP (Robert L. Nuckolls, III)
34. 08:58 PM - Re: Re: DC Power Systems Dynamics - Breakers (Robert L. Nuckolls, III)
35. 09:24 PM - Re: Circuit breaker ratings for OVP (Robert McCallum)
Message 1
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| Subject: | Re: Ongoing soap opera |
--> AeroElectric-List message posted by: "Ed Anderson" <eanderson@carolina.rr.com>
.
>
> I'm hoping that at the end, someone will translate all the information
into
> knowledge that I can use. As it is, as near as I can tell from reading
> both sides, any voltage regulator, any over voltage protection and any
> alternator will certainly kill me.
>
Could happen I suppose, but on the other hand I think there are other things
much more likely to do it {:>).
I would like to know what is the statistical likelihood of any of these
things happening? I have driven automobiles since the early 50's and have
had one alternator fail - it simply stopped producing voltage, well it
actually would produce 2.1 volts (bad diodes), but not enough. The battery
idiot light came on while driving and I immediately head for home on the
battery. Turning on the turn signal to turn into my drive way killed the
engine. But, I knew what had happened and made a bee-line for home before
the juice ran out.
Never had and have never hear of an auto alternator failing and killing the
cars electronics through over-voltage - although I have no doubt it could
and has happened. But, it must be a fairly rare occurrence given the
millions and millions of autos on the road.
I have now been flying an all electric (rotary) aircraft since 1997 and have
shed one of the two batteries I started out with (changing it each year -
but now considering going to every two years using a battery pulser to
reduce the sulfating?
But, my point is - how often does this happen in real life?? And are there
other things statistically more likely to kill me (I would imagine just
about everything else in fact - alternators are probably far, far down the
list {:>)).
Just a personal opinion of course.
Ed Anderson
Rv-6A N494BW Rotary Powered
Matthews, NC
eanderson@carolina.rr.com
Message 2
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--> AeroElectric-List message posted by: "Giffen A Marr" <gamarr@charter.net>
Suggestion
Why not set up a meeting between the individuals and review the data.
Obviously, there is concern about clamping the OV during the shutdown of the
alternator. Is it significant? Is there a safety of flight issue for the all
electronic aircraft? Does it put at risk the $$$ avionics and/or engine
electronics? Review the test data that has raised the concern, reach a
consensus, and let the rest of us know. Trying to review data on the list is
not a practical way to resolve this concern because of the complexity of the
issue.
Giff Marr
LIVP/20B 30%
Message 3
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| Subject: | Re: Alternator characteristics |
--> AeroElectric-List message posted by: "Gary Casey" <glcasey@adelphia.net>
<<I think that one of the objectives of the OVP short is to control the
voltage until the alternator shuts down.>>
<<The Panasonic data sheet says approximately 12 milliohm.>>
I'm afraid my question might get lost in the sea of comments on this
subject, but here goes: Given the data above, I calculate that a "runaway"
60-amp alternator can only raise the voltage of the battery about 0.7 volts
from it's static condition. Let's say it takes 13.5 or so for it to accept
any current, then an alternator failure should raise the voltage to only
14.2. I just don't understand the paranoia about over-voltage conditions,
as with a battery in the circuit I don't know where they come from.
Certainly an alternator cannot be allowed to run forever under that
condition, but it seems to me that if the pilot were alerted to an
over-voltage condition he would have all the time in the world to reach over
and pull the alternator CB, whether it be for the field in the case of an
externally-regulated alternator or the output breaker for an
internally-regulated alternator. That gives the pilot the option of turning
the alternator back on if the battery starts to droop, not possible with an
automatic OV "protection" system. And I guess I'll have to side against
using a device that intentionally puts in an overload as a "protection"
device. No?
(My original plan was to use an internally-regulated alternator feeding into
a 60-amp CB and that's all. No automatic OV protection - but then I let
myself get swayed by arguments on the list and went the other way.)
Gary Casey
Message 4
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| Subject: | Re: Ongoing soap opera |
--> AeroElectric-List message posted by: Dj Merrill <deej@thayer.dartmouth.edu>
Robert L. Nuckolls, III wrote:
> and be assured that the document you seek will come to pass. In
> the mean time, I think it's counter productive to push the
> conversation into hiding when so many people have expressed an
> interest in listening in.
FWIW, I agree. Please keep up the discussion public.
Most of it is over my head, but I am learning little by little.
do not archive
-Dj
--
Dj Merrill
deej@thayer.dartmouth.edu
"TSA: Totally Screwing Aviation"
Message 5
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| Subject: | Re: Points for discussion OVP//more |
--> AeroElectric-List message posted by: "Jerry Isler" <jlisler@alltel.net>
As a lowly RV owner with a Vans 35 amp alternator, solid state external
voltage regulator (VR-166?) and an AeroElectric crowbar overvoltage
protection device wired in accordance with Bob's recommendation, what does
all of this mean to me? If I experience an overvoltage condition and the
crowbar OVP device trips the field breaker, are you saying the system is
going to experience hundreds of excess amps from my 35 amp alternator for an
fraction of a second and melt my lovely RV (and me) into oblivion? Obviously
if there is an overvoltage condition on the system there is already a
failure of some sort. Are you saying the crowbar OVP will make the failure
worse?
Jerry Isler
RV4 N455J
----- Original Message -----
From: "Paul Messinger" <paulm@olypen.com>
Subject: Re: AeroElectric-List: Points for discussion OVP//more
> --> AeroElectric-List message posted by: "Paul Messinger"
<paulm@olypen.com>
>
> ----- Original Message -----
> From: "Robert L. Nuckolls, III" <b.nuckolls@cox.net>
> To: <aeroelectric-list@matronics.com>
> Subject: Re: AeroElectric-List: Points for discussion OVP//more
>
>
> > --> AeroElectric-List message posted by: "Robert L. Nuckolls, III"
> > <b.nuckolls@cox.net>
> >
> > At 08:31 AM 3/15/2005 -0500, you wrote:
> >
> >>--> AeroElectric-List message posted by: Matt Jurotich
> >><mjurotich@hst.nasa.gov>
>
> . . . but assuming your system
> > IS capable of producing a 250A trip current, is there
> > any analysis to support the notion that this is "bad"
> > for other systems in the aircraft?
> >
> > Bob . . .
>
>
Message 6
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| Subject: | Re: Alternator characteristics |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <b.nuckolls@cox.net>
At 06:12 AM 3/22/2005 -0800, you wrote:
>--> AeroElectric-List message posted by: "Gary Casey" <glcasey@adelphia.net>
>
><<I think that one of the objectives of the OVP short is to control the
>voltage until the alternator shuts down.>>
><<The Panasonic data sheet says approximately 12 milliohm.>>
>
>I'm afraid my question might get lost in the sea of comments on this
>subject, but here goes: Given the data above, I calculate that a "runaway"
>60-amp alternator can only raise the voltage of the battery about 0.7 volts
>from it's static condition.
I think you're assuming that the load impedance of a batttery
to charging currents is the same as source impedance for
delivery of energy.
See Rev B to the White Paper at:
http://www.aeroelectric.com/articles/Crowbar_OV_Protection/DC_Power_System_Dynamics_B.pdf
> Let's say it takes 13.5 or so for it to accept
>any current, then an alternator failure should raise the voltage to only
>14.2. I just don't understand the paranoia about over-voltage conditions,
>as with a battery in the circuit I don't know where they come from.
>Certainly an alternator cannot be allowed to run forever under that
>condition, but it seems to me that if the pilot were alerted to an
>over-voltage condition he would have all the time in the world to reach over
>and pull the alternator CB, whether it be for the field in the case of an
>externally-regulated alternator or the output breaker for an
>internally-regulated alternator. That gives the pilot the option of turning
>the alternator back on if the battery starts to droop, not possible with an
>automatic OV "protection" system. And I guess I'll have to side against
>using a device that intentionally puts in an overload as a "protection"
>device. No?
Close . . . In the white paper I do raise the question
as to the validity of ov protection on small alternators
ASSUMING that a good battery is in place to mitigate the
over-charging condition.
>(My original plan was to use an internally-regulated alternator feeding into
>a 60-amp CB and that's all. No automatic OV protection - but then I let
>myself get swayed by arguments on the list and went the other way.)
Which arguments? I don't recall any statements wherein the EFFECTS
of a runaway alternator were anything to brush aside. There have
been discussions about PROBABILITY of a runaway condition where
I believe the consensus is that OV in a modern alternator is
a very low probability . . . but I don't believe anyone has
suggested that it's ZERO.
So, here are the choices. Internal or external regulated
alternator. Depending on which technology is selected, applying
OV protection must take different routes because of lack
of access to the field circuit of an internally regulated
alternator.
Internally regulated alternators can be easily shut down
with no fanfare, no smoke, no stresses on components created
or exacerbated by the presence of an OV protection system.
However, there is risk to SOME internally regulated machines
when the b-lead is opened while the alternator is working
hard. We don't have definitive numbers on this risk because
we have zero knowledge of the alternators that have
suffered damage.
Should we leave OV protection off to save an alternator
that's capable of frying the rest of the system? The all
inclusive solution is to apply what techniques we know are
friendly to the task of saving an already failed alternator
(or tolerating operator induced stresses when the system
is switched on/off while loaded and at high RPM).
Now, we can discuss different ways to open the b-lead
contactor and various band-aids to stack on top of that
to accommodate the switch-flipper but once the major risk
has been caged, the rest requires assessment of the cost/
complexity/benefits ratios.
The simplest approach is to protect the airplane first
and understand the risks of random switch-flipping such
that risks to the alternator are eliminated.
Bob . . .
Message 7
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--> AeroElectric-List message posted by: "Paul Messinger" <paulm@olypen.com>
You need to read Bobs white paper and consider your comments again as you
have confused something. Or I have not made myself clear enough.
When Bob says its 7 and the simple math using his numbers comes out 70 its
a simple math error but that affects his assumptions in other math.
One NEVER uses assumptions and Always uses spec values and worst case design
to be sure the design will always meet the design intent with ANY
conbination of parts. The subject test simply does not do this.
The design also overstresses parts under worst case design rules.
Paul
----- Original Message -----
From: "Andrew Rowley" <arowley@ncable.net.au>
Subject: AeroElectric-List: Re:
> --> AeroElectric-List message posted by: Andrew Rowley
> <arowley@ncable.net.au>
>
> Paul Messinger wrote:
>
>> --> AeroElectric-List message posted by: "Paul Messinger"
>> <paulm@olypen.com>
>
>> I only wanted to define what was inside
>> the realistic range to show how ridiculous the crowbar approach was
>
> That doesn't sound like a good point to begin an objective experiment.
>
>
>> Bob then goes on with "out of the thin air conclusions" :-) that are not
>> based on any real facts and in fact the available data (again from
>> various
>> data sheets) do not support the conclusions.
>>
>> For example:
>>
>> From the report:
>>
>> ". Battery delta E for 135A load is about 2.4 volts for an internal
>> impedance of about 17 milliohms.
>>
>> About what one would expect from a two year old battery that started out
>> in
>> the 8 to 10 milliohm."
>>
>>
>> The Panasonic data sheet says approximately 12 milliohm. Approximately is
>> hardly an engineering term but it's also not 8-10 as Bob suggests for a
>> new
>> battery.
>
> These figures sound close enough to the data sheet to be usable to me. I
> don't see how the difference affects the conclusion. You used 2
> batteries for 3.5 milliohms resistance, which is even less than the 8-10
> that you are objecting to.
>
>
>> Going on we find a violation of ohms law :-)
>>
>> When I do the math I get 70 NOT 7 milliohms on the last line (for the CB)
>> which conflicts with the first line of 62 milliohms total loop
>> resistance.
>> From this and my earlier comments the entire technical analysis is
>> clearly
>> faulty.
>
> I don't see that it conflicts. It is the maximum from the
> specifications. There is no reason it can't be lower. I don't see that
> the conclusions are affected. As far as I can see it only affects the
> calculation of the average joint resistance. It seems like a nitpick,
> rather than something that puts the entire technical analysis into doubt.
>
>> I simply do not understand the massive resistance to make an improvement
>> (even the addition of 1/4 ohm is resisted).
>
> I think that one of the objectives of the OVP short is to control the
> voltage until the alternator shuts down. To do that you probably need to
> be able to take the entire output of the alternator. If you put a
> resistor there, you need to make sure it is sized according to the
> alternator output. You would also need to subtract the resistance of the
> rest of the circuit from the resistor value. At this point, it is
> probably getting unnecessarily complex.
>
>
> --
> Andrew Rowley
> arowley@ncable.net.au
>
>
>
Message 8
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| Subject: | Re: Alternator characteristics |
--> AeroElectric-List message posted by: "Paul Messinger" <paulm@olypen.com>
I have tested a battery with a constant current 40 amp supply. The battery
was a concord 25ah aircraft battery.
A battery that is fully charged acts more like a capacitor than a sink for
excess current. The test battery terminal voltage was well above 20V in
under 30 seconds and going up fast.
I have concluded (and the experts agree) that a battery will not clamp the
voltage if there is a lot of current that the battery does not need for
charging, it just goes into overcharge mode and away we go :-)
A battery is great as a capacitor for load dumps and other short term
overcurrents from the alternator but useless in the case of a long term
failure like a failed hi regulator, Thus the need for some sort of OVP.
You can consider the OVP as a voltage clamp while opening the CB that kills
the field and or opens the "B" lead.
The subject failure is quite rare.
Paul
----- Original Message -----
From: "Gary Casey" <glcasey@adelphia.net>
Subject: Re: AeroElectric-List: Alternator characteristics
> --> AeroElectric-List message posted by: "Gary Casey"
> <glcasey@adelphia.net>
>
> <<I think that one of the objectives of the OVP short is to control the
> voltage until the alternator shuts down.>>
> <<The Panasonic data sheet says approximately 12 milliohm.>>
>
> I'm afraid my question might get lost in the sea of comments on this
> subject, but here goes: Given the data above, I calculate that a
> "runaway"
> 60-amp alternator can only raise the voltage of the battery about 0.7
> volts
> from it's static condition. Let's say it takes 13.5 or so for it to
> accept
> any current, then an alternator failure should raise the voltage to only
> 14.2. I just don't understand the paranoia about over-voltage conditions,
> as with a battery in the circuit I don't know where they come from.
> Certainly an alternator cannot be allowed to run forever under that
> condition, but it seems to me that if the pilot were alerted to an
> over-voltage condition he would have all the time in the world to reach
> over
> and pull the alternator CB, whether it be for the field in the case of an
> externally-regulated alternator or the output breaker for an
> internally-regulated alternator. That gives the pilot the option of
> turning
> the alternator back on if the battery starts to droop, not possible with
> an
> automatic OV "protection" system. And I guess I'll have to side against
> using a device that intentionally puts in an overload as a "protection"
> device. No?
>
> (My original plan was to use an internally-regulated alternator feeding
> into
> a 60-amp CB and that's all. No automatic OV protection - but then I let
> myself get swayed by arguments on the list and went the other way.)
>
> Gary Casey
>
>
>
Message 9
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| Subject: | Re: Ongoing soap opera |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <b.nuckolls@cox.net>
>
>
>I'm hoping that at the end, someone will translate all the information into
>knowledge that I can use. As it is, as near as I can tell from reading
>both sides, any voltage regulator, any over voltage protection and any
>alternator will certainly kill me.
I will do that document . . . as I mentioned earlier.
I don't think anyone died JUST because their system went into
OV and toasted things. As I've mentioned many times, when I
walk up to a rental airplane, I have ZERO knowledge of that
electrical system's history. I plan to reach airport of intended
destination with NOTHING working on the panel. Whether the
panel goes black because of an ov condition, alternator craps
and battery is soggy, wires come loose . . . it doesn't matter.
The way I fly and the stuff I carry in my flight bag makes
for a high order probability of comfortably terminating the
flight.
However, people have died when a system went down, descents
had to be made through ice, windshields became non-transparent
and the pilot lost directional control on a snow covered runway
while trying to land looking out the foul weather window.
It's a classic example of how several things stack on top
of each other to influence the outcome of the experience.
This guy made a successful descent through hell-on-wings,
set up an approach, got the wheels on the runway of an
airport and died anyhow. Was it the OV condition that
killed him?
Take care lest we build emotions into your perceptions
of this discussion that are not warranted and certainly
don't advance the science. I know that's difficult because
of how our culture treats almost all discussions. Watch
the Sunday morning talking-head shows and the last thing
you find is a quest for logical stacking of simple-ideas
toward an elegant solution. EVERY discussion is a contest
with every participant wanting to feel like he/she
was the "winner".
It's difficult to watch an energetic discussion without
transferring one's own perceptions of emotional investments
into what we're watching. Try to ignore who is talking . . .
it's irrelevant. Look for the simple-ideas and science
that become the building blocks for later solutions.
When simple ideas come to light, they are inarguable
and invariable. If you're not interested in those things, that's
perfectly okay too. Hit the delete key and wait for the
consensus paper. You're not required to participate or
even observe what's going on any more than you're required
to read every book in a library. When the book of simple-
Bob . . .
Message 10
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| Subject: | Re: Ongoing soap opera |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <b.nuckolls@cox.net>
At 12:58 AM 3/22/2005 -0500, you wrote:
>--> AeroElectric-List message posted by: N1deltawhiskey@aol.com
>
>In a message dated 21-Mar-05 17:03:05 Pacific Standard Time,
>krasinski@provalue.net writes:
>Lets attack the issue, not the people.
>
>I hope there is no perception that I was attacking anyone with my post; it
>was certainly not my intent.
I didn't think you were. I did think you were frustrated with
what you may perceive as a lot of energetic blowing of the chaff . . .
<snip>
>My response was to a suggestion by one of the primary participants that some
>of the dialogue might best be moved off the list, and given MY priorities, I
>can agree with that position. At least keeping the discussion "on point"
>if it
>is to continue would be of more benefit to me. I understand that not all will
>agree with this view and take no offense at that. It is, indeed, the issue
>that matters.
I think my analogy of the library is a good one here. Would you
really want anyone (or any committee) to filter or limit what
is placed on library shelves? I know it happens all the time and
one special-interest group or another can probably take some satisfaction
in that fact. I sincerely hope that this List represent a library
of all the things participants can bring to it. Your computer is
your library card and your delete key is the method by which you
select what is interesting/useful to read.
>Opinions (of which there are many) do not need to be rebutted - they are
>simply that, the writer's opinion, regardless of its alleged factual basis.
>Facts, or alleged facts, may be challengeable. If the dialogue was
>trimmed to the
>facts, the information would be of much more use IMHO.
I'm hoping to drive to the level of simple-ideas. These are not
opinions. They are invariable and inarguable. Once a useful array
of ideas is identified, one can begin to assemble useful systems.
Here is where the crown of elegance can take on many forms and
end users can select from which ever piece of jewelry suits
their fancy. But EVERY system's design and performance should
be explained and understood at the level of simple-ideas . . .
to do less reduces the marketing or promotion of that design
to the same level as that of a product in a television infomercial.
Bob . . .
Message 11
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| Subject: | Re: Alternator characteristics |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <b.nuckolls@cox.net>
At 07:32 AM 3/22/2005 -0800, you wrote:
>--> AeroElectric-List message posted by: "Paul Messinger" <paulm@olypen.com>
>
>I have tested a battery with a constant current 40 amp supply. The battery
>was a concord 25ah aircraft battery.
>
>A battery that is fully charged acts more like a capacitor than a sink for
>excess current. The test battery terminal voltage was well above 20V in
>under 30 seconds and going up fast.
>
>I have concluded (and the experts agree) that a battery will not clamp the
>voltage if there is a lot of current that the battery does not need for
>charging, it just goes into overcharge mode and away we go :-)
>
>A battery is great as a capacitor for load dumps and other short term
>overcurrents from the alternator but useless in the case of a long term
>failure like a failed hi regulator, Thus the need for some sort of OVP.
>
>You can consider the OVP as a voltage clamp while opening the CB that kills
>the field and or opens the "B" lead.
>
>The subject failure is quite rare.
Agreed. Revision B to the White Paper discusses the battery's role
in OV dynamics. There are two or perhaps three phases to the
rise in voltage across an overcharged battery. The first is fairly
fast and operates in accordance with a shift in the battery's
chemistry to morph from energy supplier to energy absorber. There's
a transition area I've described as a "knee" in the curve before the
batter goes into the grunt mode of sopping up all the energy it can.
The third phase is a function of the battery's "load" impedance on
the overcharge source. Note that this impedance is decidedly larger
than when the battery is a source of energy.
Time from onset of OV condition to the end of the "knee" is a few
hundred milliseconds max . . . PLENTY of time for any ov detection
and mitigation system to rope the alternator and bring it to the
ground. The max voltage to be expected based on relatively hefty
alternators and batteries at or near end of life is 20 volts. This
is where the 20v for one second requirement in DO-160 came from.
It's true that an unabated OV event can carry the system to
spectacular and potentially smelly heights. But it takes a lot
of time compared to the window in which we EXPECT an ov protection
system to do its job.
Bob . . .
Message 12
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--> AeroElectric-List message posted by: rd2@evenlink.com
Bob et all,
Is there a way to modify an AP with alt-hold to select certain alt, to
select vert speed, and to be able to follow a GS? Is there a site that
explains how the altitude part works?
Thanks
Message 13
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| Subject: | Re: AeroElectric-List Digest: 33 Msgs - 03/21/05 |
--> AeroElectric-List message posted by: Speedy11@aol.com
I agree with Steve Thomas. The discussion (argument?) is healthy and
informative. I learn more every day and enjoy reading (if not understanding) all
comments on this list.
Stan Sutterfield
Tampa
www.rv-8a.net
Nac> Please move this off list. When something useful comes of your
discussions,
Nac> then share it with us. It will be readily received and appreciated.
I couldn't disagree more. This discussion is the best thing I've seen
on any list anywhere. I'm no more of an expert than the least of you
out there, but I have learned more about alternators than I've ever
dreamed about knowing despite the fact that I don't understand a lot
of it....
I'd like the discussion to continue....
If you don't like the discussion, as has been said, delete it. You
can tell in the first paragraph whether it is of interest or not. As
for me, I'd like to continue to read.
Message 14
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| Subject: | Re: Ongoing Soap Opera |
--> AeroElectric-List message posted by: Speedy11@aol.com
In a message dated 3/22/2005 2:57:38 AM Eastern Standard Time,
aeroelectric-list-digest@matronics.com writes:
Please move this off list. When something useful comes of your discussions,
then share it with us. It will be readily received and appreciated.
Mr. Windhorn, I'd prefer that you move off this list than Bob or Paul.
Still, thanks for your comments. As useless as they were, I still read and
reread them.
Do Not Archive
Stan Sutterfield
Tampa
www.rv-8a.net
Message 15
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--> AeroElectric-List message posted by: "Stein Bruch" <stein@steinair.com>
That functionality isn't easily "modified" into existance, as you're talking
about several different things that aren't related.
The Alt Hold & V.Speed are relatively easy, and both TruTrak as well as Trio
are offering a "Altitude Hold" with Vertical Speed.
The GS part is much more complex, because now you're following a NAV signal,
not a GPS or simple referential air data.
I think the easiest way to accomplish what you want is to simply buy an
exisiting autopilot with that functionality!
Just my 2 cents.
Cheers,
Stein.
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com]On Behalf Of
rd2@evenlink.com
Subject: AeroElectric-List: Auto Pilot
--> AeroElectric-List message posted by: rd2@evenlink.com
Bob et all,
Is there a way to modify an AP with alt-hold to select certain alt, to
select vert speed, and to be able to follow a GS? Is there a site that
explains how the altitude part works?
Thanks
Message 16
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| Subject: | Re: RE: 20% better efficiency ??? |
--> AeroElectric-List message posted by: "Paul Messinger" <paulm@olypen.com>
I was referencing specifically to the old 0-360 lyc.
The numbers you state are very good and may be better then ours.
As for fuel flow there is good data but no current data as the dyno fuel
flow card is in for repair and has been for some time.
The engine of interest is a very modern modified auto engine with auto type
fuel and spark computer control systems. I had expected better / more
current by now data but the dyno card has been a hold up.
The data I used was from a side by side flyoff between an earlier version of
the engine vs. the 0-360 in identical aircraft where the aircraft were flown
the same time and after landing the amount of fuel expended was measured.
Both aircraft had on board fuel flow measuring systems.
Both had similar fuel flow at 100% of power but at 75% the auto conversion
was 20+% lower fuel flow. Airspeeds were matched for this test.
The Lyc was the 180 HP version and the auto conversion was at the time 200
HP. Its now 230 HP (231.5 +/- as measured) on the certified dyno best
engine case.. Gear reduction to prop speeds IE 2700 max prop rpm.
On the other hand its low noise and the very low vibration, partly due to
the hither frequencies of the higher rpms due to the geat reduction. Runs on
any grade of auto gas or 100LL.
Paul
----- Original Message -----
From: "George Braly" <gwbraly@gami.com>
Subject: AeroElectric-List: RE: 20% better efficiency ???
> --> AeroElectric-List message posted by: "George Braly" <gwbraly@gami.com>
>
>
> Paul,
>
> You write:
>
>>>Personally I feel the future of general aviation is with automotive
>>>derived
> conversions where fuel consumption is significantly lower(more than
> 20%) - -<<
>
> The Brake Specific Fuel Consumption is the universal yardstick of piston
> engine efficiency.
>
> Can you point me to any data on any spark ignition automotive engine that
> delivers 75% of its rated power to the propeller flange, at prop
> appropriate RPM's, and has a BSFC anywhere close to the existing 0.385
> lb/hr/hp that one gets from a 300 Hp TCM engine?
>
>
> I am unaware of any. Even the highly regarded Porsche Mooney (FADEC)
> engine had to struggle to get down to 0.425.
>
>
> Regards, George
>
>
> ---
>
>
>
Message 17
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| Subject: | Diodes across relay coils |
--> AeroElectric-List message posted by: "Paul Messinger" <paulm@olypen.com>
For decades 99.999% of the engineering world recommended and used the common
rectifier diode across inductors like relay coils to suppress the inductive
spike that happens when the power to the inductor is interrupted.
Many (including Bob) have stated that while this practice extends the start
of opening time of the relay it does not change the opening speed once the
relay contacts start opening. Thus the only down side to use of the diode is
a delay in the start of opening. Normally this is not important.
For example the common contactor used for starting or battery connection
will open in 10 ms with no diode and it takes 50 ms with a diode.
A friend sent me several links including one at Potter and Brumfield (a
major relay manufacturer) that not only had a comparison table (of
suppression devices) but a comment on what the use of a diode really does.
I have extracted part of that comment below and also included at the end of
this post the links for the interested.
""Effects of Coil Suppression on Relay Dynamics and Life
Even though the use of coil suppression is becoming more significant,
relays are normally designed without taking the dynamic impact of
suppressors into account. The optimum switching life (for normally-open
contacts) is therefore obtained with a totally unsuppressed relay and
statements of rated electrical life are usually based on this premise. The
successful "breaking" of a DC load requires that the relay contacts move
to open with a reasonably high speed.
A typical relay will have an accelerating motion of its armature toward the
unenergized rest position during drop-out. The velocity of the armature at
the instant of contact opening will play a significant role in the relay's
ability to avoid "tack welding" by providing adequate force to break any
light welds made during the "make" of a high current resistive load (or one
with a high in-rush current). It is the velocity of the armature that is
most
affected by coil suppression. If the suppressor provides a conducting path,
thus allowing the stored energy in the relay's magnetic circuit to decay
slowly, the armature motion will be retarded and the armature may even
temporarily reverse direction. The reversing of direction and re-closing of
the contacts (particularly when combined with inductive loads) often leads
to random, intermittent "tack welding" of the contacts such that the relay
may free itself if operated again or even jarred slightly.
Based upon the impact on armature motion and optimizing for normallyopen
contacts, the best suppression method is to use a silicon transient
suppressor diode. This suppressor will have the least effect on relay
dropout
dynamics since the relay transient will be allowed to go to a
predetermined voltage level and then permit current to flow with a low
impedance. This results in the stored energy being quickly dissipated by
the suppressor. Transient suppressor diodes are available as bi-directional
components and permit the relay to be non-polarized when installed
internally. Note that if a uni-directional transient suppressor is used, a
rectifier diode must be placed in series with it to block normal current
flow and it has little advantage over the use of a zener diode. ""
This and a table comparing different types of suppressors (see the below
links) clearly indicates a couple of things.
First 99.99% of engineers have been using the wrong type of suppressor for
many years.
The simple diode is perhaps the worst choice(see the table of comparisons at
the links). In the case of power contactors the use of a simple diode
actually slow the mechanical opening of the contacts quite a lot and
increases the likely hood of contact welding.
I have tested this last year in the load dump testing and recorded large
multiple contact bouncing.
I have removed all the simple diodes across relays and replaced them with by
directional transorbs and also supplied parts to the local builders as well.
Here are a couple of links, There is also one in Europe that I cannot find
right now with the same conclusions.
http://relays.tycoelectronics.com/application.asp
http://relays.tycoelectronics.com/kilovac/appnotes/transients.stm
Paul
Message 18
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| Subject: | Re: Alternator characteristics |
--> AeroElectric-List message posted by: "Paul Messinger" <paulm@olypen.com>
The alternator is clamped with transorbs and the OVP takes over if the OV is
for longer than 200 ms in our design and a few ms in Bob's design. The
reason for the difference in timing is due to different approaches to the
same fundamental concerns. Two of several good ways to mitigate the
concerns. Lots of bad ways and usually more than one good way to solve most
any concern.
In the case of a "B" lead contactor there is the possibility it will not
open until some time after the CB is opened (It is slow in my testing) and
in that case the transorbs again act to clamp the OV.
Paul
----- Original Message -----
From: "Andrew Rowley" <arowley@ncable.net.au>
Subject: Re: AeroElectric-List: Alternator characteristics
> --> AeroElectric-List message posted by: Andrew Rowley
> <arowley@ncable.net.au>
>
> Paul Messinger wrote:
>> And finally the Eric Jones and recommended by me
>> approach where the OV is instantly clamped to a safe level and then the
>> alternator is taken off line and there is no chance of any post CB
>> popping
>> load dump residual voltage to deal with as the circuit is clamped before
>> during and after.
>
> How is the OV clamped? The only ways I can think of to control the
> voltage are to divert the current like the crowbar does, or to have a
> regulator-like device that the alternator output goes through.
>
> The second option would raise reliability questions for me. Having seen
> common problems with regulators in the motorcycle world, I have formed
> the opinion that it is not easy to build a device that can carry the
> constant output of an alternator and cope with real world problems like
> poor connections and inadequate cooling.
>
> --
> Andrew Rowley
> arowley@ncable.net.au
>
>
>
Message 19
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| Subject: | Re: Alternator characteristics |
--> AeroElectric-List message posted by: "Paul Messinger" <paulm@olypen.com>
One emergency mode of operation considered for an electrically dependent
engine is the case where the battery(s) are off line for what ever reason
including open cell or contactor failure.
With no battery a large load dump; turning off the hyd pump, or landing gear
electric motor can cause the bus voltage to go to 30-50 volts depending on
what load is already on the bus and how big the current being turned off is.
The battery will absorb most any size load dump if its on line. Using a
25,000 mfd capacitor has been suggedted in the "no battery mode" but even
that sized capacitor may not keep the bus voltage under 20 v and if there is
a OVP set at 16.2 V (as recommended) its very likely that will trip. Once
off line, most alternators will not restart without a battery for the
initial voltage/current required.
Lots of different things to consider and often a different solution is
needed depending on the configuration.
Paul
----- Original Message -----
From: "Glaeser, Dennis A" <dennis.glaeser@eds.com>
Subject: AeroElectric-List: Re: Alternator characteristics
> --> AeroElectric-List message posted by: "Glaeser, Dennis A"
> <dennis.glaeser@eds.com>
>
> I have a question regarding:
>
> --snip--
> WE still have to wait 30 ms or longer for the "B" lead contactor to open
> and
> during this there is no OV protection and the load dump from the stored
> energy is still dumping onto the bus. If there is a battery present its
> likely a non event voltage wise. However if the mode of operation is
> alternator only then there can be 20+ volt voltage spike on top of the 12v
> nominal voltage. A mag equipped engine will press on but your avionics may
> be toasted
> --snip--
>
> I probably missed something along the way, but when would the mode of
> operation be 'alternator only'? Is this to allow for a failed battery, or
> some other scenario? I thought the purpose of the On-On-On switch (or
> Cessna split rocker) was to preclude taking the battery off-line while the
> alternator is connected.
>
> Dennis Glaeser
>
>
>
Message 20
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| Subject: | Circuit breaker ratings for OVP |
--> AeroElectric-List message posted by: "Paul Messinger" <paulm@olypen.com>
One of the likely circuit breaker candidates is the W23 5 amp unit. Its
reported this is used by 3 major certificated aircraft and is approved by
the FAA.
This CB, as are all the others I have looked at, define the 'time to open
range' at various over current levels up to 1,000% of rating. Interesting
that they all stop at 1,000%. That is 50 amps for a 5 amp breaker. Its also
10 times rated current.
Now the W23 specification data sheet states the following:
Resettable Overload capacity: Ten times rated current.
What does this mean??
This is defined in the industry as:
"RESETTABLE OVERLOAD CAPACITY
* Represents the maximum current the circuit protector is capable of
interrupting without damaging itself."
What does this mean??
It means that the CB may not meet specifications if the current being broken
exceeds ten times (or in this case 50 amps) its ratings.
I checked with a long time IA and he said that means the CB must be replaced
if there is a known overcurrent trip on a critical to flight item. The
alternator is considered a critical to flight component. Bsically if a part
is known to have been subjected to an out of specification condition that
might affest its function it must be replaced, testing is not good enough.
The only conclusion I can come to is that any crowbar design that is not
current limited to 50 amps will require the CB to be replaced if its tripped
by and crowbar OVP in a certificated aircraft.
For experimental its not the same but who would not want to replace a
potentially damaged CB that might not work as specified??
As I have previously suggested there is a simple fix to those who are using
the crowbar OVP and that is to add a 1/4 ohm resistor in series that will
limit the current to 50 amps or less and will not prevent the proper and
intended function of the OVP.
Both Bob and I have agreed that the typical OVP being discussed has a
tripping current in excess of 100 amps, that we disagree on the amount of
current over 100 amps is not really important.
I do not know if the certified LR-x series of regulators can overcurrent the
CB (worst case over 50 amps) but its worth investigating.
I can see no reason for not making this improvement and eliminating the
potential damage to the CB from being over stressed.
Note that the ability of the CB to break up to 2,000 amps is very different
from being able to survive this with no damage. Essentially what the mfgr's
are saying is that the CB is reusable as a CB up to ten times its ratings
and will open under hundreds of times its ratings but then should be treated
like a fuse and be replaced.
Paul
Message 21
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| Subject: | Re: Alternator characteristics |
--> AeroElectric-List message posted by: "Paul Messinger" <paulm@olypen.com>
My point was not that OVP will prevent problems but that there are so many
out there who think that the battery will prevent OVP or at least keep the
OV under sort of control.
I think we can agree that some OVP method is needed regardless of the
likelyhood of a total runaway alternator no matter how unlikely because of
the potential results.
My concern is there are many thousands of aircraft out there with NO OVP of
any kind.
However there are different types and methods of OVP and I believe that one
size does not fit all cases.
Paul
----- Original Message -----
From: "Robert L. Nuckolls, III" <b.nuckolls@cox.net>
Subject: Re: AeroElectric-List: Alternator characteristics
> --> AeroElectric-List message posted by: "Robert L. Nuckolls, III"
> <b.nuckolls@cox.net>
>
> At 07:32 AM 3/22/2005 -0800, you wrote:
>
>>--> AeroElectric-List message posted by: "Paul Messinger"
>><paulm@olypen.com>
>>
>>I have tested a battery with a constant current 40 amp supply. The battery
>>was a concord 25ah aircraft battery.
>>
>>A battery that is fully charged acts more like a capacitor than a sink for
>>excess current. The test battery terminal voltage was well above 20V in
>>under 30 seconds and going up fast.
>>
>>I have concluded (and the experts agree) that a battery will not clamp the
>>voltage if there is a lot of current that the battery does not need for
>>charging, it just goes into overcharge mode and away we go :-)
>>
>>A battery is great as a capacitor for load dumps and other short term
>>overcurrents from the alternator but useless in the case of a long term
>>failure like a failed hi regulator, Thus the need for some sort of OVP.
>>
>>You can consider the OVP as a voltage clamp while opening the CB that
>>kills
>>the field and or opens the "B" lead.
>>
>>The subject failure is quite rare.
>
>
> Agreed. Revision B to the White Paper discusses the battery's role
> in OV dynamics. There are two or perhaps three phases to the
> rise in voltage across an overcharged battery. The first is fairly
> fast and operates in accordance with a shift in the battery's
> chemistry to morph from energy supplier to energy absorber. There's
> a transition area I've described as a "knee" in the curve before the
> batter goes into the grunt mode of sopping up all the energy it can.
> The third phase is a function of the battery's "load" impedance on
> the overcharge source. Note that this impedance is decidedly larger
> than when the battery is a source of energy.
>
> Time from onset of OV condition to the end of the "knee" is a few
> hundred milliseconds max . . . PLENTY of time for any ov detection
> and mitigation system to rope the alternator and bring it to the
> ground. The max voltage to be expected based on relatively hefty
> alternators and batteries at or near end of life is 20 volts. This
> is where the 20v for one second requirement in DO-160 came from.
>
> It's true that an unabated OV event can carry the system to
> spectacular and potentially smelly heights. But it takes a lot
> of time compared to the window in which we EXPECT an ov protection
> system to do its job.
>
> Bob . . .
>
>
>
Message 22
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| Subject: | Re: Circuit breaker ratings for OVP |
--> AeroElectric-List message posted by: "Matt Prather" <mprather@spro.net>
Hi Paul,
You make an interesting point. I wonder, how often we will know that
a tripped breaker did so within the spec'ed range? In other words, if a
breaker trips because of a wiring fault, is there any way to know that the
1000% spec wasn't violated. I suppose what that suggests is that if
your airplane chafes off a piece of insulation and then pops a breaker,
the only approved way to return it to service is to repair the wire, chafe
protect it, AND replace the breaker. Is that right?
Regards,
Matt-
VE N34RD, C150 N714BK
> --> AeroElectric-List message posted by: "Paul Messinger"
> <paulm@olypen.com>
>
> One of the likely circuit breaker candidates is the W23 5 amp unit. Its
> reported this is used by 3 major certificated aircraft and is approved
> by the FAA.
>
> This CB, as are all the others I have looked at, define the 'time to
> open range' at various over current levels up to 1,000% of rating.
> Interesting that they all stop at 1,000%. That is 50 amps for a 5 amp
> breaker. Its also 10 times rated current.
>
> Now the W23 specification data sheet states the following:
>
> Resettable Overload capacity: Ten times rated current.
>
> What does this mean??
>
> This is defined in the industry as:
>
> "RESETTABLE OVERLOAD CAPACITY
> * Represents the maximum current the circuit protector is capable of
> interrupting without damaging itself."
>
> What does this mean??
> It means that the CB may not meet specifications if the current being
> broken exceeds ten times (or in this case 50 amps) its ratings.
>
> I checked with a long time IA and he said that means the CB must be
> replaced if there is a known overcurrent trip on a critical to flight
> item. The alternator is considered a critical to flight component.
> Bsically if a part is known to have been subjected to an out of
> specification condition that might affest its function it must be
> replaced, testing is not good enough.
>
> The only conclusion I can come to is that any crowbar design that is not
> current limited to 50 amps will require the CB to be replaced if its
> tripped by and crowbar OVP in a certificated aircraft.
>
> For experimental its not the same but who would not want to replace a
> potentially damaged CB that might not work as specified??
>
> As I have previously suggested there is a simple fix to those who are
> using the crowbar OVP and that is to add a 1/4 ohm resistor in series
> that will limit the current to 50 amps or less and will not prevent the
> proper and intended function of the OVP.
>
> Both Bob and I have agreed that the typical OVP being discussed has a
> tripping current in excess of 100 amps, that we disagree on the amount
> of current over 100 amps is not really important.
>
> I do not know if the certified LR-x series of regulators can overcurrent
> the CB (worst case over 50 amps) but its worth investigating.
>
> I can see no reason for not making this improvement and eliminating the
> potential damage to the CB from being over stressed.
>
> Note that the ability of the CB to break up to 2,000 amps is very
> different from being able to survive this with no damage. Essentially
> what the mfgr's are saying is that the CB is reusable as a CB up to ten
> times its ratings and will open under hundreds of times its ratings but
> then should be treated like a fuse and be replaced.
>
>
> Paul
>
>
Message 23
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--> AeroElectric-List message posted by: rd2@evenlink.com
Stein,
>The Alt Hold & V.Speed are relatively easy, and both TruTrak as well as Trio
>are offering a "Altitude Hold" with Vertical Speed.
Thanks for the above info.
>The GS part is much more complex, because now you're following a NAV signal,
>not a GPS or simple referential air data.
The AP already has 1 nav input, but that is used to follow the localizer.
>I think the easiest way to accomplish what you want is to simply buy an
>exisiting autopilot with that functionality!
This one part will cost me more than 2 cents - more like quite a few grand. :)
(I got a proposal for over 10K; nocando). I'd like to read up on the
subjest, but can't find sources yet. Not to say that I'd do a mod and trust
it to follow the GS in hard IFR.
>Just my 2 cents.
>Cheers,
>Stein.
Cheers here too
Rumen
BTW I love the machined pins I got from you.
Message 24
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| Subject: | Re: DC Power Systems Dynamics - Breakers |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <b.nuckolls@cox.net>
At 07:12 AM 3/22/2005 -0800, you wrote:
>--> AeroElectric-List message posted by: "Paul Messinger" <paulm@olypen.com>
>
>You need to read Bobs white paper and consider your comments again as you
>have confused something. Or I have not made myself clear enough.
>
>When Bob says its 7 and the simple math using his numbers comes out 70 its
>a simple math error but that affects his assumptions in other math.
Paul,
I'll suggest that the value was not an assumption but a math error.
The real assumption was that the breaker should be assigned a resistance
based on a specified maximum voltage drop. Better that the real resistance
of the breaker be measured. I did this and found it to be 38 milliohms.
This tracks with practical reality. I would expect the specified voltage
drop and associated resistance value to be end-of-life values and
it's not surprising to find this number to be perhaps twice the factory
new number. It also pushes total of connection and crimp resistances
into a more reasonable realm and eliminates the need to evaluate the
effects of "better wiring" thus eliminating one whole paragraph from
the paper.
>One NEVER uses assumptions and Always uses spec values . . .
Not all assumptions (or extrapolations) are evil if they
rest on reasonable foundation . . .
> . . . and worst case design
>to be sure the design will always meet the design intent with ANY
>conbination of parts. The subject test simply does not do this.
I disagree here and permit me to illustrate the foundation.
If I design and airplane, should the design goal be to
allow assembly with Grade 5 hardware store bolts or is it
more practical and safer to SPECIFY Grade 8 fasteners?
If I kit up a digital voltmeter with a goal of displaying
bus volts to 1% accuracy, can I use 5% tolerance parts in
the voltage dividers?
System performance is often predicated on utilization
of specific parts. Not a new concept in aviation . . . but while
we're free to choose from a wider variation of components in
the OBAM community, I'll suggest that the choices are never
without boundaries.
If I understand your suggestion as to "combinations of parts"
do I deduce correctly that the major variable is the kind
of circuit breaker used? Keep in mind that the test was NOT
an evaluation of any particular part selection but a simple
illustration of a methodology for demonstrating the effects
of parts, wire, connections and battery impedance on the
performance of a system. It's just a collection of simple
tools applicable to investigation of specific installations
on airplanes or any other test setup.
I'll readily admit to not having considered that someone
might purchase a totally unknown quality breaker and combine
it with the crowbar ov module. That didn't occur to me because
we were supplying recommended (but not SPECIFIED) breakers.
I'll see to it that the installation instructions for this
product are modified to SPECIFY recommended parts so as to
prevent a breaker pulled off a garden tractor from finding
its way into somebody's alternator system. In the
mean time, would it be a useful exercise to identify and
caution against breakers with extra-ordinarily long operating
times? I'd be pleased to test/confirm the suitability or
non-suitability of any breaker you suggest.
With respect to exceeding specified limits on the operation
of breakers recommended for this application, I've captured
information off an Eaton/Mechanical Products data sheet
which I've published on my website at:
http://www.aeroelectric.com/Mfgr_Data/Breakers/Eaton_4200.pdf
This breaker is used by the thousands at RAC and is part of
the samples I'm gathering to evaluate in the experiment.
I think the commercial version of this breaker is the one
sold by B&C as MP Model 4200 as opposed to the mil-spec
parts in the bins at RAC.
Sections of the data sheet have been excerpted and added
to the Report which has been updated to Rev -C-
http://www.aeroelectric.com/articles/Crowbar_OV_Protection/DC_Power_System_Dynamics_C.pdf
This revision corrects the math errors previously identified,
adds the data extracted from the breaker specifications
and offers a foundation for what may have been dubbed
assumptions. I'll suggest they are valid interpretations
of the specifications or rational extrapolations from that
data.
Still working on Rev -D-
>The design also overstresses parts under worst case design rules.
Not sure which part you're referring to here: For the SCR?
Yes, the MCR-69 is operating at the ragged edge for short
wires (and way out the roof for zero length wires) but OV
protection is a rare, generally isolated event. Further,
when the installation instructions are modified to recommend
care in selection the companion breaker, we'll also set up
guidelines for minimum total wire length so as to make sure
no-one installs the module right at the breaker.
SCR's used in the L-series controllers are fatter and
much more robust than the MCR-69 and it's TO-220 cousins.
We'll wear out breakers before we push one of those
puppies off the wagon.
If you're referring to the breaker, I'll rely on data
extracted from manufacturer's published literature for
the breaker SPECIFIED in this experiment and for others
to be specified in the installation instructions for a
crowbar OV protected system.
> >
> >> Bob then goes on with "out of the thin air conclusions" :-) that are not
> >> based on any real facts and in fact the available data (again from
> >> various data sheets do not support the conclusions.
> >>
> >> For example:
> >>
> >> From the report:
> >>
> >> ". Battery delta E for 135A load is about 2.4 volts for an internal
> >> impedance of about 17 milliohms.
> >>
> >> About what one would expect from a two year old battery that started out
> >> in the 8 to 10 milliohm."
> >>>
> >> The Panasonic data sheet says approximately 12 milliohm. Approximately is
> >> hardly an engineering term but it's also not 8-10 as Bob suggests for a
> >> new battery.
Approximately is indeed an engineering term. It's often used to
make sure the listener/reader is not lulled into some sense of accuracy
in a value where accuracy is either suspect or the variable in
question is very loose. For the convenience of our readers,
I've posted the Panasonic data sheet at:
http://www.aeroelectric.com/Mfgr_Data/Batteries/Panasonic_1217.pdf
On several occasions I've measured the source impedance of new
1217 batteries and most of the time they're better than 12 millohms
but why are we quibbling about this? The experiment measured and
stated the source impedance as the battery as it was. We further
extrapolated what the performance would be with ANY other battery having
a lower impedance and discovered that battery impedance doesn't
drive the overall performance. If the soggy 17 milliohm
device were replaced with the gold plated 1 millohm device, overall
performance is affected only slightly. The the driving variables are
wiring,
breaker and switch impedances.
> >> When I do the math I get 70 NOT 7 milliohms on the last line (for the CB)
> >> which conflicts with the first line of 62 milliohms total loop
> >> resistance. From this and my earlier comments the entire technical
> analysis is
> >> clearly faulty.
Error noted and corrected. But since the mis-calculated value
was only part of the total, MEASURED loop impedance, the effect
of correcting the error only shifted more resistance to the breaker
and away from terminals and connections. Net change to the conclusions was
zero. How does this make the entire analysis faulty?
> >> I simply do not understand the massive resistance to make an improvement
> >> (even the addition of 1/4 ohm is resisted).
I don't know that there IS "massive" resistance to any changes.
I'm wanting to understand their value and effect. Please don't
interpret a lack of enthusiasm for improvements to be a reluctance
to change. I've sold hundreds of these systems. B&C has sold
thousands of these systems. It's a really good thing to upgrade
the performance of your products when ever it can be shown to
add value. On the other side, if the improvement is made to
correct some shortcoming in the design or recommendations for
installation, we need to partition that off for examination too.
Do I owe thousands of customers a modified instruction sheet?
Are systems in place for nearly a decade at risk? Should
we be recalling product based on discovery of a real screw-up?
When 400-700A crowbar currents are cited as a risk to the users
of this philosophy it gets my attention. It argues with
what I believed was a long held and reasonably solid understanding.
I hope it's clear that I'm intently interested in examining that
understanding to validate, modify or discard as evaluation of the
investigation directs.
This is another reason for carrying on this conversation out
in the open. It has nothing to do with who invented what or
who recommends what . . . our readers need to have confidence
in everyone's recommendations. That cannot be enhanced by deliberating
behind closed doors.
Bob . . .
Message 25
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<canard-aviators@yahoogroups.com>, <defiantflyers@yahoogroups.com>,
<Cozy_Builders@mailman.qth.net>, <aeroelectric-list@matronics.com>
| Subject: | Grandsons Aircraft Ride at Pensacola on March 24. |
--> AeroElectric-List message posted by: "Eric Ruttan" <ericruttan@chartermi.net>
This question was sent to me at the Canard Aviation Forum. I found it
rather touching, and with David's permission, I am forwarding it to all the
relevant lists I know.
Please reply to David directly. I have no further information.
Thank you,
Eric Ruttan. One of the canardaviationforum.dmt.net admins
P.S.
If this post is so off topic as to harm or offend, I apologize in advance.
The fault is mine not David's.
----- Original Message -----
From: "David Dorris @ Canard Aviation Forum" <ddorris@brsm.org>
Subject: Canard Aviation Forum Contact Us Form - Site Feedback
> The following message was sent to you via the Canard Aviation Forum
Contact Us form by David Dorris.
>
> --------------------------------
>
> I know this isn't in your area, maybe, but I have a problem. My grandsons
are coming to Pensacola on March 24 and I have promised to take them up in a
small plane or helicopter. Do you know where I might be able to get in
tough with someone that offers that service.
>
> Thank you very much.
>
> David Dorris
> ddorris@brsm.org
> --------------------------------
Message 26
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| Subject: | Circuit breaker ratings for OVP |
--> AeroElectric-List message posted by: "Kingsley Hurst" <khurst@taroom.qld.gov.au>
Paul M,
You said :-
As I have previously suggested there is a simple fix to those who are
using
the crowbar OVP and that is to add a 1/4 ohm resistor in series that
will
limit the current to 50 amps or less and will not prevent the proper and
intended function of the OVP.
What wattage are we talking about here please Paul or doesn't it matter
owing to the small duration of the high current event ?
Regards
Kingsley Hurst in Oz.
Message 27
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--> AeroElectric-List message posted by: <bakerocb@cox.net>
AeroElectric-List message previously posted by: "Bob McDevitt"
<mcdevitt@sympatico.ca>
<<I am having a problem that has me stumped. The problem occurs with the
engine running or off. As I am doing all my trouble shooting with the engine
off, I will use that mode for all descriptions.
Master on, radio on, the bus voltage reads 12.5 volts, when the PTT switch
is pressed, the voltage rises to 13.5 volts.
I have replaced all suspect cables (battery + and -) starter cable as well
as the master and starter relays. Problem still exists.
I have disconnected the alternator B lead to no avail. Can anyone offer a
suggestion for a cure? Bob McDevitt>>
2/22/5005
Hello Bob McDevitt, I agree with Bob Nuckolls -- your are seeing the effects
of EMI (Electro Magnetic Interference), sometimes called RF (Radio
Frequency) interference, on the measuring device.
What voltmeter are you using to measure this increase? The one installed in
your panel or a separate handheld meter connected to the bus? If you are
using the meter in the panel, try a separate handheld meter. If you are
using a separate hand held meter try to borrow a different (and maybe
better) one with regard to resisting EMI.
If the problem persists then try the dummy load technique on your radio
transmitter as recommended by Bob Nuckolls. Please let us know how this is
resolved. Thanks.
OC
Message 28
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| Subject: | Re: DC Power Systems Dynamics - Breakers |
--> AeroElectric-List message posted by: "Paul Messinger" <paulm@olypen.com>
You have apparently missed my main point. Its not what you or I have done
with a few tests.
We MUST do a worst case analysis of any and all parts used or recommended
and if specific parts are required they need top be specified. You have
specified parts for the OVP but not specified specific CB part #.
If you take a low 'worst case' current and the worst case long open time
from the CB spec of the CB you actually tested there is no way its going to
be less than 100 milliseconds. Reminder the 7274 CB has a 50 amp trip time
of 0.046 to 0.8 amps. This at 25C and what about when its cold it can trip
10% longer with possible cockpit temps in treasonable climes.
As for the SCR I reviewed the specs for the one called out and its also
rated 300 amps at 50 Hz pulses which is lower than My test. I have found the
die attach bond wires are the really weak point in semi's.
As for batteries again what you or I test is NOT what another production run
or another MFGR's battery will test out at.
I disagree on assumptions and really disagree on taking a few samples and
making general conclusions. Good aerospace engineering requires a worst on
worst analysis. Further if a specific part or resistance is required it must
be specified.
I have more embedded comments below
Paul
----- Original Message -----
From: "Robert L. Nuckolls, III" <b.nuckolls@cox.net>
Subject: AeroElectric-List: Re: DC Power Systems Dynamics - Breakers
> --> AeroElectric-List message posted by: "Robert L. Nuckolls, III"
> <b.nuckolls@cox.net>
>
> At 07:12 AM 3/22/2005 -0800, you wrote:
>
>>--> AeroElectric-List message posted by: "Paul Messinger"
>><paulm@olypen.com>
>>
>>
>>One NEVER uses assumptions and Always uses spec values . . .
>
> Not all assumptions (or extrapolations) are evil if they
> rest on reasonable foundation . . .
I should not have used 'never' (almost never) but your paper sure led me and
others to assume that for example 400 amps or 100 ms time to open was not
reasonable but a simple worst on worst specification values along with a
range of real wires etc would suggest otherwise.
In the case where you have dual batteries capable of 3000 amps short current
(7 milliohms each and 3.5 in parallel)and 2 ft of #4 and 2 ft of #6 and the
OVP with 1" leads across the CB and right below the main ground return which
is also 2 ft of #6 the wiring resistance is very low in the real world.
The above is a real representation of my acft less the contactor inline
resistance 0.001 ohm measured) from each battery to the main bus.
I suggest your test example was closer to the other maxi wiring and battery
resistance. I did not measure circuit resistance and the testing was quite
consistent over several weeks.
>
>
>> . . . and worst case design
>>to be sure the design will always meet the design intent with ANY
>>conbination of parts. The subject test simply does not do this.
>
> I disagree here and permit me to illustrate the foundation.
> If I design and airplane, should the design goal be to
> allow assembly with Grade 5 hardware store bolts or is it
> more practical and safer to SPECIFY Grade 8 fasteners?
That is not what you have done. I have never seen a worst case analysis.
Grade 5 parts might be ok IF the design was based on that level of strength
and had the proper design margins built in. One never designs to
specification limits but always derates the parts in my engineering world
either mechanical or electrical there is derating or design margins the
included
> If I kit up a digital voltmeter with a goal of displaying
> bus volts to 1% accuracy, can I use 5% tolerance parts in
> the voltage dividers?
>
> > If I understand your suggestion as to "combinations of parts"
> do I deduce correctly that the major variable is the kind
> of circuit breaker used? Keep in mind that the test was NOT
> an evaluation of any particular part selection but a simple
> illustration of a methodology for demonstrating the effects
> of parts, wire, connections and battery impedance on the
> performance of a system. It's just a collection of simple
> tools applicable to investigation of specific installations
> on airplanes or any other test setup.
But it appeared to have, as an objective, a lot of supporting analysis to
suggest the design was good and safe. Again no use of available data sheet
limits but nearly 100% use of measured values which are far from the max in
the data sheets. Not that the design is good and safe but we need something
more than a test and assumptions as proof
> I'll readily admit to not having considered that someone
> might purchase a totally unknown quality breaker and combine
> it with the crowbar ov module. That didn't occur to me because
> we were supplying recommended (but not SPECIFIED) breakers.
I have above pointed out that the breakers suggested can be a lot slower
than your tests. Also I recommend that you either do a worst case analysis
and or specify the breaker brand and or part # as well as the minimum and
maximum wiring from the battery to the OVP etc if the design requires it to
prevent overly long pop times or too high currents.
>
> I'll see to it that the installation instructions for this
> product are modified to SPECIFY recommended parts so as to
> prevent a breaker pulled off a garden tractor from finding
> its way into somebody's alternator system. In the
> mean time, would it be a useful exercise to identify and
> caution against breakers with extra-ordinarily long operating
> times? I'd be pleased to test/confirm the suitability or
> non-suitability of any breaker you suggest.
My only 'real to me' required change to the do it your self OVP is the
addition of a 1/4 ohm resistor to limit the current to 50 amps max. I can
see no down side to this other than the addition to parts in the field. It
eliminates the objections of very high current and resolves any questions of
overcurrent harming the CB.
Frankly I have tested 3 different brands and you have tested a 4th one. All
are commonly used on acft and 3 of the 4 are available thru Aircraft Spruce
etc. ALL have 500-800 ms long times to open at 1000% of rated load (50 amps)
and that is as I have posted the maximum current that you can break and
retain the original CB ratings.
>
> With respect to exceeding specified limits on the operation
> of breakers recommended for this application, I've captured
> information off an Eaton/Mechanical Products data sheet
> which I've published on my website at:
>
> http://www.aeroelectric.com/Mfgr_Data/Breakers/Eaton_4200.pdf
>
> This breaker is used by the thousands at RAC and is part of
> the samples I'm gathering to evaluate in the experiment.
> I think the commercial version of this breaker is the one
> sold by B&C as MP Model 4200 as opposed to the mil-spec
> parts in the bins at RAC.
This is apparently identical in specs to the 77XX breakers we both have
tested and retail the 800 ms max long opening time.
>
>>The design also overstresses parts under worst case design rules.
>
> Not sure which part you're referring to here: For the SCR?
> Yes, the MCR-69 is operating at the ragged edge for short
> wires (and way out the roof for zero length wires) but OV
> protection is a rare, generally isolated event. Further,
> when the installation instructions are modified to recommend
> care in selection the companion breaker, we'll also set up
> guidelines for minimum total wire length so as to make sure
> no-one installs the module right at the breaker.
>
> SCR's used in the L-series controllers are fatter and
> much more robust than the MCR-69 and it's TO-220 cousins.
> We'll wear out breakers before we push one of those
> puppies off the wagon.
I cannot comment on the LR regulators but the Do it your self OVP specified
essentially the same SCR with regard to ratings. Actually I was unable to
apparently damage the specified SCR with currents that exceeded 700 amps in
a couple of tests. Not that I would recommend their use as that would be out
of the specified range.
>
> If you're referring to the breaker, I'll rely on data
> extracted from manufacturer's published literature for
> the breaker SPECIFIED in this experiment and for others
> to be specified in the installation instructions for a
> crowbar OV protected system.
>
>> >
>> >> Bob then goes on with "out of the thin air conclusions" :-) that are
>> >> not
>> >> based on any real facts and in fact the available data (again from
>> >> various data sheets do not support the conclusions.
>> >>
>> >> For example:
>> >>
>> >> From the report:
>> >>
>> >> ". Battery delta E for 135A load is about 2.4 volts for an internal
>> >> impedance of about 17 milliohms.
>> >>
>> >> About what one would expect from a two year old battery that started
>> >> out
>> >> in the 8 to 10 milliohm."
>> >>>
>> >> The Panasonic data sheet says approximately 12 milliohm. Approximately
>> >> is
>> >> hardly an engineering term but it's also not 8-10 as Bob suggests for
>> >> a
>> >> new battery.
>
> Approximately is indeed an engineering term. It's often used to
> make sure the listener/reader is not lulled into some sense of
> accuracy
> in a value where accuracy is either suspect or the variable in
> question is very loose. For the convenience of our readers,
> I've posted the Panasonic data sheet at:
Apprx as used for engineering calculations is new to me. I have never seen
it used to support analysis where the results would or should be used beyond
some simple test of concept.
> On several occasions I've measured the source impedance of new
> 1217 batteries and most of the time they're better than 12 millohms
> but why are we quibbling about this?
Only that you do not require Panasonic and Panasonic does not warrant the
resistance. Thus regardless of how unimportant it is to the analysis its not
good to use data that may not be represent the entire world of possible
batteries. I have a battery post on the many types of batteries available
not mentioning the specialty brands available at the garden shops etc. These
all come in the same size shape and general ratings 12V 160-18AH. If
Panasonic is required specific that only Panasonic be used.
> The experiment measured and
> stated the source impedance as the battery as it was. We further
> extrapolated what the performance would be with ANY other battery
> having
> a lower impedance and discovered that battery impedance doesn't
> drive the overall performance. If the soggy 17 milliohm
> device were replaced with the gold plated 1 millohm device, overall
> performance is affected only slightly. The the driving variables are
> wiring,
> breaker and switch impedances.
>
>> >> When I do the math I get 70 NOT 7 milliohms on the last line (for the
>> >> CB)
>> >> which conflicts with the first line of 62 milliohms total loop
>> >> resistance. From this and my earlier comments the entire technical
>> analysis is
>> >> clearly faulty.
>
> Error noted and corrected. But since the mis-calculated value
> was only part of the total, MEASURED loop impedance, the effect
> of correcting the error only shifted more resistance to the breaker
> and away from terminals and connections. Net change to the conclusions
> was
> zero. How does this make the entire analysis faulty?
>
>> >> I simply do not understand the massive resistance to make an
>> >> improvement
>> >> (even the addition of 1/4 ohm is resisted).
>
> I don't know that there IS "massive" resistance to any changes.
> I'm wanting to understand their value and effect. Please don't
> interpret a lack of enthusiasm for improvements to be a reluctance
> to change. I've sold hundreds of these systems. B&C has sold
> thousands of these systems. It's a really good thing to upgrade
> the performance of your products when ever it can be shown to
> add value. On the other side, if the improvement is made to
> correct some shortcoming in the design or recommendations for
> installation, we need to partition that off for examination too.
I and friends have had reported to us several dozen cases of false tripping
of the 'do it your self' OVP. I have personally (by accident) found a
condition where it false tripped 100% of the time. I then built up a second
unit and it performed the same. Then "US" :-) engineers got together and
found the likely cause in the design is susceptibility to a specific type of
contact bounce as I was using a contactor to connect the Load dump loads of
10 -40 amps. The OVP tripped every time the load was connected while the
alternator was on line.
The OVP module was built on a perf board 1" by 1.5".
Adding 0.1 mfd, and then 10 mfd tant failed to work but adding 1,000 mfd
cured the problem and false tripping went from 100% to 0%. I have not
previously reported this as I feel its an unusual setup but now wonder if
the small number of false trips we have been told about could have been
related to something similar.
>
> Do I owe thousands of customers a modified instruction sheet?
> Are systems in place for nearly a decade at risk? Should
> we be recalling product based on discovery of a real screw-up?
> When 400-700A crowbar currents are cited as a risk to the users
> of this philosophy it gets my attention. It argues with
> what I believed was a long held and reasonably solid understanding.
I do not know. I have demonstrated to myself and others that what I am
measuring IE 400 amp currents is real. I agree its a setup with low
resistance wiring and never expected your large response to the currents. In
the case where there is no electrically dependent engine involved its no big
deal to have a momentary drop in the battery voltage. Where battery voltage
is important its a different matter and should be discussed independently as
its not just a OVP issue.
>
> I hope it's clear that I'm intently interested in examining that
> understanding to validate, modify or discard as evaluation of the
> investigation directs.
>
> This is another reason for carrying on this conversation out
> in the open. It has nothing to do with who invented what or
> who recommends what . . . our readers need to have confidence
> in everyone's recommendations. That cannot be enhanced by deliberating
> behind closed doors.
As you might have noted I disagreed with my east coast partner (Eric) when
He suggested a committee.
However I would hope this could be the end of this discussion between us. We
have both extensively stated our opinions and its time to move on.
As I have said above the addition of a 1/4 ohm resistor is my only remaining
concern ant that is to satisfy the CB mfgrs requirements to replace any CB
that opens under more than 10X rated currents.
Thanks for your participation in this sometimes warm discussion. Fortunately
just smoke no fire (joke that is please other readers) :-)
Paul
Message 29
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| Subject: | Circuit breaker ratings for OVP |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <b.nuckolls@cox.net>
At 08:57 AM 3/23/2005 +1000, you wrote:
>--> AeroElectric-List message posted by: "Kingsley Hurst"
><khurst@taroom.qld.gov.au>
>
>Paul M,
>
>You said :-
>As I have previously suggested there is a simple fix to those who are
>using the crowbar OVP and that is to add a 1/4 ohm resistor in series that
>will limit the current to 50 amps or less and will not prevent the proper and
>intended function of the OVP.
>
>What wattage are we talking about here please Paul or doesn't it matter
>owing to the small duration of the high current event ?
Is your alternator externally regulated? Then keep in mind that adding
resistance in series with the ov protection module will reduce its
ability to pull the field voltage down even BEFORE the breaker trips.
In fact, adding this much resistance insures that the OV event will
continue until the breaker opens. During the trip event, the series
resistor will have to carry about 50A at about 10v for an instantaneous
dissipation level of about 500 watts. Most wirewound resistor folks
will rate their produces at 10x rated power for 5 seconds. So assuming
a 10 watt, 0.25 ohm resistor will safely handle 100 watts for 5 seconds
(current of 20A) this calculates to an Isquared*t value 20*20*5 or
2,000.
Okay, for a 50A event, an Isquared*t of 2000 yields a maximum time
of 2000/2500 or about .8 seconds. This suggests that a 10W resistor
is plenty hefty enough to accomplish the task. A 5W resistor would
be good for .4 seconds . . . also fine.
See ALSR series wirewounds on Digikey at
http://dkc3.digikey.com/PDF/T051/1026.pdf
An ALSR5J-.25-ND (0.25 ohm, 5w) resistor is in stock and would
cost you about $1.50
If your alternator is internally regulated, then the OVM has no immediate
effect on the runaway condition. Increasing the series resistance
the OVM-14 only increases breaker opening time. However, given that
the internally regulated alternator control system operates nicely through
a 2A breaker, all you need to do is replace your existing breaker with
a 2A sub-miniature breaker. See:
http://bandc.biz/cgi-bin/ez-catalog/cat_display.cgi?7X358218#CB1
These have an internal resistance of well OVER .25 ohms. 0.30 ohms
in fact. This will have the same effect as adding series resistance
to the OVM-14. Either way, the resistor cited above or replacing the
breaker will have the desired effect.
Bob . . .
Message 30
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| Subject: | Re: Ongoing Soap Opera |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <b.nuckolls@cox.net>
>> Please move this off list. When something useful comes of your
discussions,
>> then share it with us. It will be readily received and appreciated.
> Mr. Windhorn, I'd prefer that you move off this list than Bob or Paul.
Gently, gently my friend. Doug's been around here for quite some time
and has been a good citizen of the List. I presume that his attendance
here demonstrates his sense of value for spending the time to join
us. I fully understand how someone who is not interested in lengthy,
detailed dissertations might find it frustrating . . . and he's certainly
entitled to express them. It's helpful of folks who ARE interested in
the work to assist those with limited time and interest to acquire what
they need/want.
There are only 4 reasons for folks to communicate with each other.
To inform (share facts and simple-ideas), entertain (to each his
own but a little humor or the occasional war story is fine by me), to
persuade (only necessary if you're a preacher, politician, or
lawyer) or to inflict discomfort or injury (self explanatory).
May I suggest that you evaluate your words in these contexts and
decide the purpose for which they are offered. I'd really like to
believe that everyone here wants to know the 'good stuff', have a
good time learning it and will craft their activities in support
of that goal.
Bob . . .
Message 31
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| Subject: | Re: Circuit breaker ratings for OVP |
--> AeroElectric-List message posted by: Andrew Rowley <arowley@ncable.net.au>
Robert L. Nuckolls, III wrote:
> If your alternator is internally regulated, then the OVM has no immediate
> effect on the runaway condition. Increasing the series resistance
> the OVM-14 only increases breaker opening time. However, given that
> the internally regulated alternator control system operates nicely through
> a 2A breaker, all you need to do is replace your existing breaker with
> a 2A sub-miniature breaker. See:
>
> http://bandc.biz/cgi-bin/ez-catalog/cat_display.cgi?7X358218#CB1
>
>
> These have an internal resistance of well OVER .25 ohms. 0.30 ohms
> in fact. This will have the same effect as adding series resistance
> to the OVM-14. Either way, the resistor cited above or replacing the
> breaker will have the desired effect.
Is the location of the resistor in the circuit significant? It seems
like if you put a resistor after the circuit splits between the OVM and
the alternator disconnect contactor, the contactor will stay closed
until after the breaker trips. On the other hand, if the resistor is
before the 2 circuits divide, you are improving the chances of the
contactor opening before the breaker trips, at the cost of having the
contactor current always running through the resistor.
Using the 2A breaker of course gives you the second scenario.
--
Andrew Rowley
arowley@ncable.net.au
Message 32
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| Subject: | Re: Circuit breaker ratings for OVP |
--> AeroElectric-List message posted by: Andrew Rowley <arowley@ncable.net.au>
Robert L. Nuckolls, III wrote:
> If your alternator is internally regulated, then the OVM has no immediate
> effect on the runaway condition. Increasing the series resistance
> the OVM-14 only increases breaker opening time. However, given that
> the internally regulated alternator control system operates nicely through
> a 2A breaker, all you need to do is replace your existing breaker with
> a 2A sub-miniature breaker. See:
>
> http://bandc.biz/cgi-bin/ez-catalog/cat_display.cgi?7X358218#CB1
>
>
> These have an internal resistance of well OVER .25 ohms. 0.30 ohms
> in fact. This will have the same effect as adding series resistance
> to the OVM-14. Either way, the resistor cited above or replacing the
> breaker will have the desired effect.
Is the location of the resistor in the circuit significant? It seems
like if you put a resistor after the circuit splits between the OVM and
the alternator disconnect contactor, the contactor will stay closed
until after the breaker trips. On the other hand, if the resistor is
before the 2 circuits divide, you are improving the chances of the
contactor opening before the breaker trips, at the cost of having the
contactor current always running through the resistor.
Using the 2A breaker of course gives you the second scenario.
--
Andrew Rowley
arowley@ncable.net.au
Message 33
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| Subject: | Re: Circuit breaker ratings for OVP |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <b.nuckolls@cox.net>
Hmmmm . . . I note that the 10x rated limit for surviving repeated trips
seems to be an industry standard practice for most breakers offered.
One might guess that the limits to the plots in the graph I excerpted
at 1000% imply the same thing. I don't find it in words on the Eaton
data sheet like for most others on the 'net. I found some $low$ breakers
out there rated at only 6x for resetable trips.
Interesting. When we crafted the original crowbar system for the Turbine
Bonanza project, we were bound by the Beech spec for 50 ov trips in a row
with the 51st trip having to be as effective as the first.I don't know
how many qual cycles we conducted on various versions using the same 5A
breaker in the fixture . . . with crowbar currents that ran
no less than 200A and sometimes as high as 300A. I'll bet that
one breaker stood up to over 1000 40x to 60x events although . . . I don't
having testing it for trip calibration after that many cycles. The
breaker never failed to reset. I've got a call into my breaker buddy
at Eaton/Cutler-Hammer to see if he can offer any clarification on this
ubiquitous 10x figure. I know I've discussed this system with him several
times over the past 25 years and he didn't raise any flags. You've raised
an interesting question!
Matt's question is interesting too . . . I'll ask around out at RAC
and see what the policy is for maintenance after a hard-fault trips
on a breaker in an airplane. I've never heard of a replace-the-breaker-too
policy but that doesn't mean it isn't doesn't exist. I can find no
reference to the practice in AC43-13 but I seem to recall someone speaking
about it some time back and I'm not even sure it was in an airplane.
Bob . . .
At 01:02 PM 3/22/2005 -0700, you wrote:
>--> AeroElectric-List message posted by: "Matt Prather" <mprather@spro.net>
>
>Hi Paul,
>
>You make an interesting point. I wonder, how often we will know that
>a tripped breaker did so within the spec'ed range? In other words, if a
>breaker trips because of a wiring fault, is there any way to know that the
>1000% spec wasn't violated. I suppose what that suggests is that if
>your airplane chafes off a piece of insulation and then pops a breaker,
>the only approved way to return it to service is to repair the wire, chafe
>protect it, AND replace the breaker. Is that right?
>
>
>Regards,
>
>Matt-
>VE N34RD, C150 N714BK
>
> > --> AeroElectric-List message posted by: "Paul Messinger"
> > <paulm@olypen.com>
> >
> > One of the likely circuit breaker candidates is the W23 5 amp unit. Its
> > reported this is used by 3 major certificated aircraft and is approved
> > by the FAA.
> >
> > This CB, as are all the others I have looked at, define the 'time to
> > open range' at various over current levels up to 1,000% of rating.
> > Interesting that they all stop at 1,000%. That is 50 amps for a 5 amp
> > breaker. Its also 10 times rated current.
> >
> > Now the W23 specification data sheet states the following:
> >
> > Resettable Overload capacity: Ten times rated current.
> >
> > What does this mean??
> >
> > This is defined in the industry as:
> >
> > "RESETTABLE OVERLOAD CAPACITY
> > * Represents the maximum current the circuit protector is capable of
> > interrupting without damaging itself."
> >
> > What does this mean??
> > It means that the CB may not meet specifications if the current being
> > broken exceeds ten times (or in this case 50 amps) its ratings.
> >
> > I checked with a long time IA and he said that means the CB must be
> > replaced if there is a known overcurrent trip on a critical to flight
> > item. The alternator is considered a critical to flight component.
> > Bsically if a part is known to have been subjected to an out of
> > specification condition that might affest its function it must be
> > replaced, testing is not good enough.
> >
> > The only conclusion I can come to is that any crowbar design that is not
> > current limited to 50 amps will require the CB to be replaced if its
> > tripped by and crowbar OVP in a certificated aircraft.
> >
> > For experimental its not the same but who would not want to replace a
> > potentially damaged CB that might not work as specified??
> >
> > As I have previously suggested there is a simple fix to those who are
> > using the crowbar OVP and that is to add a 1/4 ohm resistor in series
> > that will limit the current to 50 amps or less and will not prevent the
> > proper and intended function of the OVP.
> >
> > Both Bob and I have agreed that the typical OVP being discussed has a
> > tripping current in excess of 100 amps, that we disagree on the amount
> > of current over 100 amps is not really important.
> >
> > I do not know if the certified LR-x series of regulators can overcurrent
> > the CB (worst case over 50 amps) but its worth investigating.
> >
> > I can see no reason for not making this improvement and eliminating the
> > potential damage to the CB from being over stressed.
> >
> > Note that the ability of the CB to break up to 2,000 amps is very
> > different from being able to survive this with no damage. Essentially
> > what the mfgr's are saying is that the CB is reusable as a CB up to ten
> > times its ratings and will open under hundreds of times its ratings but
> > then should be treated like a fuse and be replaced.
> >
> >
> > Paul
> >
> >
>
>
>--
>No virus found in this incoming message.
>
>
>-- incoming mail is certified Virus Free.
Bob . . .
--------------------------------------------------------
< Throughout history, poverty is the normal condition >
< of man. Advances which permit this norm to be >
< exceeded -- here and there, now and then -- are the >
< work of an extremely small minority, frequently >
< despised, often condemned, and almost always opposed >
< by all right-thinking people. Whenever this tiny >
< minority is kept from creating, or (as sometimes >
< happens) is driven out of a society, the people >
< then slip back into abject poverty. >
< >
< This is known as "bad luck". >
< -Lazarus Long- >
<------------------------------------------------------>
http://www.aeroelectric.com
Message 34
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| Subject: | Re: DC Power Systems Dynamics - Breakers |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <b.nuckolls@cox.net>
At 05:09 PM 3/22/2005 -0800, you wrote:
>--> AeroElectric-List message posted by: "Paul Messinger" <paulm@olypen.com>
>
>You have apparently missed my main point. Its not what you or I have done
>with a few tests.
>
>We MUST do a worst case analysis of any and all parts used or recommended
>and if specific parts are required they need top be specified. You have
>specified parts for the OVP but not specified specific CB part #.
Agreed
>If you take a low 'worst case' current and the worst case long open time
>from the CB spec of the CB you actually tested there is no way its going to
>be less than 100 milliseconds. Reminder the 7274 CB has a 50 amp trip time
>of 0.046 to 0.8 amps. This at 25C and what about when its cold it can trip
>10% longer with possible cockpit temps in treasonable climes.
>
>As for the SCR I reviewed the specs for the one called out and its also
>rated 300 amps at 50 Hz pulses which is lower than My test. I have found the
>die attach bond wires are the really weak point in semi's.
Yes . . . the plastic molded parts seem to be more robust than
the formerly popular TO-3 metal cans. The metal parts were always
considered "superior" and in many ways they were . . . but their
die bond wires hung out in space and were a lot faster to fuse than
for the plastic parts. In the extremes, I seem to recall opening
bond wires in metal parts and fusing junctions in plastic parts
>As for batteries again what you or I test is NOT what another production run
>or another MFGR's battery will test out at.
The battery wasn't offered as a spectrum supply but simply an
experimental test source that could be quantified at the measured
17 milliohms. Performance of other batteries could be extrapolated
based solely on a hypothetical source impedance. The point was to
illuminate the effect of battery impedance on the experiment.
>I disagree on assumptions and really disagree on taking a few samples and
>making general conclusions. Good aerospace engineering requires a worst on
>worst analysis. Further if a specific part or resistance is required it must
>be specified.
Absolutely. What conclusions have I drawn in the experiment paper.
>I have more embedded comments below
>
>Paul
>
>----- Original Message -----
>From: "Robert L. Nuckolls, III" <b.nuckolls@cox.net>
>To: <aeroelectric-list@matronics.com>
>Subject: AeroElectric-List: Re: DC Power Systems Dynamics - Breakers
>
>
> > --> AeroElectric-List message posted by: "Robert L. Nuckolls, III"
> > <b.nuckolls@cox.net>
> >
> > At 07:12 AM 3/22/2005 -0800, you wrote:
> >
> >>--> AeroElectric-List message posted by: "Paul Messinger"
> >><paulm@olypen.com>
> >>
> >>
> >>One NEVER uses assumptions and Always uses spec values . . .
> >
> > Not all assumptions (or extrapolations) are evil if they
> > rest on reasonable foundation . . .
>
>I should not have used 'never' (almost never) but your paper sure led me and
>others to assume that for example 400 amps or 100 ms time to open was not
>reasonable but a simple worst on worst specification values along with a
>range of real wires etc would suggest otherwise.
>
>In the case where you have dual batteries capable of 3000 amps short current
>(7 milliohms each and 3.5 in parallel)and 2 ft of #4 and 2 ft of #6 and the
>OVP with 1" leads across the CB and right below the main ground return which
>is also 2 ft of #6 the wiring resistance is very low in the real world.
>
>The above is a real representation of my acft less the contactor inline
>resistance 0.001 ohm measured) from each battery to the main bus.
>
>I suggest your test example was closer to the other maxi wiring and battery
>resistance. I did not measure circuit resistance and the testing was quite
>consistent over several weeks.
Not sure about "maxi" wiring . . . do you mean maximum loop resistance?
The total lengths of wire in the experiment were 24" of 20AWG (20 mOhms)
and 6" of 10AWG (0.5 mOhms). The point was to craft a minimum wiring
scenario . . . if wired per instructions supplied with the OVM-14 or per
any of the Z-figures, what is the likelihood that any installation would
have LESS resistance than the experiment . . . and what would be the
effects
of varying battery capabilities. The experiment shows that wiring and the
circuit breaker are major contributors and have the greatest effects on
potential fault current thorough the crowbar device.
To achieve a 400A crowbar current, the total loop resistance must be
on the order of 26 milliohms. If you have a 3.5 mohm battery and a
bus feeder of 1 mohm then this leaves one to make the crowbar connections
with zero length leads and to find a breaker that runs 21.5 millohms.
This may indeed represent a worst case but one has to really work
to create it. Airplanes are put together with serviceable chunks of
wire and I believed that the experiment illustrated an exemplar
worst case for the low end of as-installed loop resistance.
> >
> >> . . . and worst case design
> >>to be sure the design will always meet the design intent with ANY
> >>conbination of parts. The subject test simply does not do this.
> >
> > I disagree here and permit me to illustrate the foundation.
> > If I design and airplane, should the design goal be to
> > allow assembly with Grade 5 hardware store bolts or is it
> > more practical and safer to SPECIFY Grade 8 fasteners?
>
>That is not what you have done. I have never seen a worst case analysis.
>Grade 5 parts might be ok IF the design was based on that level of strength
>and had the proper design margins built in. One never designs to
>specification limits but always derates the parts in my engineering world
>either mechanical or electrical there is derating or design margins the
>included
>
> > If I kit up a digital voltmeter with a goal of displaying
> > bus volts to 1% accuracy, can I use 5% tolerance parts in
> > the voltage dividers?
> >
> > > If I understand your suggestion as to "combinations of parts"
> > do I deduce correctly that the major variable is the kind
> > of circuit breaker used? Keep in mind that the test was NOT
> > an evaluation of any particular part selection but a simple
> > illustration of a methodology for demonstrating the effects
> > of parts, wire, connections and battery impedance on the
> > performance of a system. It's just a collection of simple
> > tools applicable to investigation of specific installations
> > on airplanes or any other test setup.
>
>But it appeared to have, as an objective, a lot of supporting analysis to
>suggest the design was good and safe. Again no use of available data sheet
>limits but nearly 100% use of measured values which are far from the max in
>the data sheets. Not that the design is good and safe but we need something
>more than a test and assumptions as proof.
What have I assumed? The purpose of the experiment thus far
is to simply illustrate how DIFFICULT it is to get a 400A
or larger crowbar event and to inquire as to the conditions
that produced measurements you cited. You tell me that the
crowbar device was located right at the breaker . . . still
difficult to drive the loop resistance to the requisite The next steps
will be to discuss
timing dynamics. The last revision shows that a battery
slows down an OV even so much that the protective circuitry
can stop for a cheeseburger and fries before it needs to
pull the plug on the runaway alternator. My OVP designs
come out of a long history of Mil-Std-704 descriptions
of NORMAL transients to expect on a generator only
system . . hence the relatively short time delays for step
response. But as long as a battery is on line, one can just
about run anything from .5 to 2 seconds and not affect the
level of protection. But as soon as you take the battery
out, we need to go back to the original timing but not so
fast that the system nuisance trips.
> > I'll readily admit to not having considered that someone
> > might purchase a totally unknown quality breaker and combine
> > it with the crowbar ov module. That didn't occur to me because
> > we were supplying recommended (but not SPECIFIED) breakers.
>
>I have above pointed out that the breakers suggested can be a lot slower
>than your tests. Also I recommend that you either do a worst case analysis
>and or specify the breaker brand and or part # as well as the minimum and
>maximum wiring from the battery to the OVP etc if the design requires it to
>prevent overly long pop times or too high currents.
Agreed. We'll do that.
> >
> > I'll see to it that the installation instructions for this
> > product are modified to SPECIFY recommended parts so as to
> > prevent a breaker pulled off a garden tractor from finding
> > its way into somebody's alternator system. In the
> > mean time, would it be a useful exercise to identify and
> > caution against breakers with extra-ordinarily long operating
> > times? I'd be pleased to test/confirm the suitability or
> > non-suitability of any breaker you suggest.
>
>My only 'real to me' required change to the do it your self OVP is the
>addition of a 1/4 ohm resistor to limit the current to 50 amps max. I can
>see no down side to this other than the addition to parts in the field. It
>eliminates the objections of very high current and resolves any questions of
>overcurrent harming the CB.
Agreed for the internally regulated alternator. The internally
regulated alternator poses new questions. We're still okay if
the battery stays on line because the increased opening time
of the breaker with the 50A limit is no big deal. If the battery
is off line, then the crowbar's ability to pull down directly on
the alternator (and hopefully stall it) has been compromised with
the .25 rise in load impedance. I'll look at this. My alternator
test stand gets here tomorrow night.
>Frankly I have tested 3 different brands and you have tested a 4th one. All
>are commonly used on acft and 3 of the 4 are available thru Aircraft Spruce
>etc. ALL have 500-800 ms long times to open at 1000% of rated load (50 amps)
>and that is as I have posted the maximum current that you can break and
>retain the original CB ratings.
>
> >
> > With respect to exceeding specified limits on the operation
> > of breakers recommended for this application, I've captured
> > information off an Eaton/Mechanical Products data sheet
> > which I've published on my website at:
> >
> > http://www.aeroelectric.com/Mfgr_Data/Breakers/Eaton_4200.pdf
> >
> > This breaker is used by the thousands at RAC and is part of
> > the samples I'm gathering to evaluate in the experiment.
> > I think the commercial version of this breaker is the one
> > sold by B&C as MP Model 4200 as opposed to the mil-spec
> > parts in the bins at RAC.
>
>This is apparently identical in specs to the 77XX breakers we both have
>tested and retail the 800 ms max long opening time.
> >
> >>The design also overstresses parts under worst case design rules.
> >
> > Not sure which part you're referring to here: For the SCR?
> > Yes, the MCR-69 is operating at the ragged edge for short
> > wires (and way out the roof for zero length wires) but OV
> > protection is a rare, generally isolated event. Further,
> > when the installation instructions are modified to recommend
> > care in selection the companion breaker, we'll also set up
> > guidelines for minimum total wire length so as to make sure
> > no-one installs the module right at the breaker.
> >
> > SCR's used in the L-series controllers are fatter and
> > much more robust than the MCR-69 and it's TO-220 cousins.
> > We'll wear out breakers before we push one of those
> > puppies off the wagon.
>
>I cannot comment on the LR regulators but the Do it your self OVP specified
>essentially the same SCR with regard to ratings. Actually I was unable to
>apparently damage the specified SCR with currents that exceeded 700 amps in
>a couple of tests.
gee . . . I'm still trying to figure out how you get 700 amps.
<snip>
> > On several occasions I've measured the source impedance of new
> > 1217 batteries and most of the time they're better than 12 millohms
> > but why are we quibbling about this?
>
>Only that you do not require Panasonic and Panasonic does not warrant the
>resistance. Thus regardless of how unimportant it is to the analysis its not
>good to use data that may not be represent the entire world of possible
>batteries. I have a battery post on the many types of batteries available
>not mentioning the specialty brands available at the garden shops etc. These
>all come in the same size shape and general ratings 12V 160-18AH. If
>Panasonic is required specific that only Panasonic be used.
I'm still mystified as to this exchange. I used the 1217 because it
was sitting under the bench and handy. There were larger and
smaller batteries under there that would have sufficed as well
once their effects on the experiment were understood. Only
then could the effects of any other battery could be deduced. Any
battery would have sufficed for the purpose of exploring how one
gets a 400A crowbar event. This wasn't about requiring or specifying
anything, it was about trying to understand how you achieved
numbers you cited.
>I and friends have had reported to us several dozen cases of false tripping
>of the 'do it your self' OVP. I have personally (by accident) found a
>condition where it false tripped 100% of the time. I then built up a second
>unit and it performed the same. Then "US" :-) engineers got together and
>found the likely cause in the design is susceptibility to a specific type of
>contact bounce as I was using a contactor to connect the Load dump loads of
>10 -40 amps. The OVP tripped every time the load was connected while the
>alternator was on line.
Yes, every scr can be triggered with a fast dv/dt event on the
supply line. The early installations of the SD-20 in Bonanzas would
trip when the landing and taxi lights were switched on simultaneously.
Turns out the Potter-Brumfield breaker switches . . .
(See http://www.aeroelectric.com/Pictures/W31_1.jpg )
are about the most gawd-awful bouncers anyone has ever seen. I'd
put the OVM-14 and close cousins into the lab for the DO-160 conducted
spike and noise susceptibility tests but the noise these switches
put out when switching 150 watt halogen lamps far exceeded the
DO-160 limits. We had to modify the regulators to accommodate this
situation. The OVM-14 was modified too to reduce gate-to-cathode
resistor to 10 ohms from 220 ohms like we did in the Bonanza regulators.
>Adding 0.1 mfd, and then 10 mfd tant failed to work but adding 1,000 mfd
>cured the problem and false tripping went from 100% to 0%. I have not
>previously reported this as I feel its an unusual setup but now wonder if
>the small number of false trips we have been told about could have been
>related to something similar.
Good question. I've had a lot of conversations about nuisance
trips over the years. The vast majority have been cured by
installing the spike catcher across an offending relay or
contactor. I've had perhaps a half dozen of the DIY projects
that would trip when a transmitter was keyed. The thing was built
on too large a scale and placed in a plastic box. The production
OVM-14 is quite compact and seems to be immune to RFI problems
and resistant to dv/dt (spike) events after the gate resistor
was dropped to 10 ohms.
I wouldn't have tried to filter off dv/dt effects with anode
to cathode capacitance. The filter has to grunt the noise
source impedance at the bus level. By tying the gate down,
you take advantage of weak coupling of noise through the anode-gate
capacitance. Besides the large parallel capacitance would
drive the initial crowbar trip current out the roof. Is THIS
how you measured 700A in the SCR?
>As I have said above the addition of a 1/4 ohm resistor is my only remaining
>concern ant that is to satisfy the CB mfgrs requirements to replace any CB
>that opens under more than 10X rated currents.
I've noted your concern and I'll research why this didn't bubble
up as an issue a long time ago. I still need to noodle out the
effects of this change as a generic OV protection device and
then make more specific recommendations in our installation
instructions and the Z-figures.
>Thanks for your participation in this sometimes warm discussion. Fortunately
>just smoke no fire (joke that is please other readers) :-)
I'll continue with the development of the white paper with
exploration of suggested changes and repairs to errors noted.
You are invited to comment on the continuing effort or not as you
see fit. Your input to date has been thought provoking and
helpful.
Bob . . .
Message 35
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| Subject: | Re: Circuit breaker ratings for OVP |
--> AeroElectric-List message posted by: Robert McCallum <robert.mccallum2@sympatico.ca>
Bob;
Although the "time to trip" charts stop at 1000% of the breakers rating,
the specifications you have published here
http://www.aeroelectric.com/Mfgr_Data/Breakers/Eaton_4200.pdf
under interrupting capacity at 28 volts state that for a 4200 series
breaker of 5 amp rating, the interrupting capacity is "unlimited" (seems
a bit high?) Certainly more than 10X. Further the same spec sheet says
that a 7.5 amp breaker is capable of interrupting 2000 amps. This is
266X its nominal rating. If you look at a 25 amp it's 80X nominal. I
realize that this doesn't specify the number of times the breaker will
survive these currents, but it does state that they are capable of
taming currents of these magnitudes. How do these figures impact on the
10X theory and where does the 10X information show up in the
specifications? In a parallel but totally different scenario, household
breakers of 15 amp rating, to be certified for use in your home, (at
least here in Canada) must be capable of interrupting 10,000 amps
minimum. That's 667X nominal value. Unrelated, I know, but ----- These
numbers and those stated by Eaton in the charts cited seem to be at odds
with the 10X value. Yes????? No??????
Bob McC
Robert L. Nuckolls, III wrote:
>--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <b.nuckolls@cox.net>
>
>Hmmmm . . . I note that the 10x rated limit for surviving repeated trips
>seems to be an industry standard practice for most breakers offered.
>One might guess that the limits to the plots in the graph I excerpted
>at 1000% imply the same thing. I don't find it in words on the Eaton
>data sheet like for most others on the 'net. I found some $low$ breakers
>out there rated at only 6x for resetable trips.
><snip>
>Interesting. <snip>
>Bob . . .
>
>
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