Today's Message Index:
----------------------
1. 12:57 AM - Re: White Paper on Crowbar OV Protection (Andrew Rowley)
2. 05:45 AM - Re: White Paper on Crowbar OV Protection (BobsV35B@aol.com)
3. 06:01 AM - Re: White Paper on Crowbar OV Protection (BobsV35B@aol.com)
4. 06:18 AM - OV protection (Gary Casey)
5. 06:18 AM - 21V Transformer (Charlie Brame)
6. 06:24 AM - Re: Using a 115 volt 400 hz device in a 12 (Matt Jurotich)
7. 07:07 AM - GPS Annunciator (Vern W.)
8. 07:28 AM - Re: 21V Transformer (John Danielson)
9. 08:02 AM - Re: Using a 115 volt 400 hz device in a 12 (Jim Oke)
10. 08:02 AM - Re: Using a 115 volt 400 hz device in a 12 (Ken)
11. 08:11 AM - Re: GPS Annunciator (BobsV35B@aol.com)
12. 08:49 AM - Re: White Paper on Crowbar OV Protection (Matt Prather)
13. 08:50 AM - Re: GPS Annunciator (Jim Stone)
14. 09:15 AM - Re: GPS Annunciator (Vern W.)
15. 09:41 AM - Re: GPS Annunciator (BobsV35B@aol.com)
16. 09:43 AM - Re: GPS Annunciator (Jim Oke)
17. 09:50 AM - Re: Using a 115 volt 400 hz device in a 12 (Robert L. Nuckolls, III)
18. 03:02 PM - Re: White Paper on Crowbar OV Protection (Andrew Rowley)
19. 03:27 PM - Re: White Paper on Crowbar OV Protection (Andrew Rowley)
20. 03:55 PM - headset level to mic level for recording (Dan Checkoway)
21. 04:49 PM - Re: White Paper on Crowbar OV Protection (Matt Prather)
22. 04:58 PM - Re: headset level to mic level for recording (rv-9a-online)
23. 06:08 PM - Re: White Paper on Crowbar OV Protection (Andrew Rowley)
24. 06:14 PM - Re: Points for discussion OVP//more (Paul Messinger)
25. 06:39 PM - Re: Points for discussion OVP//more (Paul Messinger)
26. 06:46 PM - Re: Alternator Control (Paul Messinger)
27. 06:59 PM - Re: White Paper on Crowbar OV Protection (Matt Prather)
28. 07:43 PM - Re: White Paper on Crowbar OV Protection (Paul Messinger)
29. 07:43 PM - Re: Using a 115 volt 400 hz device in a 12 (Jerzy Krasinski)
30. 08:00 PM - Re: OV protection debate (Paul Messinger)
Message 1
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| Subject: | Re: White Paper on Crowbar OV Protection |
--> AeroElectric-List message posted by: Andrew Rowley <arowley@ncable.net.au>
Matt Prather wrote:
> Hello (I am guessing) Andrew,
>
> I apologize if I sounded frosty. No introductions necessary. I just like to
> poke fun at people when they don't sign their emails in any way. Maybe a
> silly hangup on my part.
>
> I do believe your questions have been answered in the archive. Maybe
> someone else will re-answer them.
OK, fair enough :-) I have changed email address and email program a few
times, and use different addresses for regular email and various lists,
so I guess my sig got lost along the way. You should still be able to
see my name in the From: field though?
I was trying to contribute to the current debate, but maybe it has all
been covered in the past. That's the nature of the internet though - and
one advantage of rehashing old information is that new people learn
stuff they didn't even know they should be asking about :-)
Message 2
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| Subject: | Re: White Paper on Crowbar OV Protection |
--> AeroElectric-List message posted by: BobsV35B@aol.com
In a message dated 3/18/2005 1:10:17 A.M. Central Standard Time,
arowley@ncable.net.au writes:
Who am I? A builder in Australia, building a Rans S6S.
Good Morning ????
That is very nice to know, but we have still not seen a name.
The convention on this list seems to be to sign your message with a name,
your type or style of aircraft and your location, often the airport from
which you fly.
We are a nosy bunch.
And; Welcome Aboard!
Happy Skies,
Old Bob
AKA
Bob Siegfried
Ancient Aviator
Stearman N3977A
Brookeridge Airpark LL22
Downers Grove, IL 60516
630 985-8502
Do Not Archive
Message 3
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| Subject: | Re: White Paper on Crowbar OV Protection |
--> AeroElectric-List message posted by: BobsV35B@aol.com
In a message dated 3/18/2005 2:58:24 A.M. Central Standard Time,
arowley@ncable.net.au writes:
You should still be able to
see my name in the From: field though?
Good Morning Andrew,
Unfortunately, the name doesn't come through with all programs. It did on
this message, but not the others.
Happy Skies,
Old Bob
AKA
Bob Siegfried
Ancient Aviator
Stearman N3977A
Brookeridge Airpark LL22
Downers Grove, IL 60516
630 985-8502
Message 4
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--> AeroElectric-List message posted by: "Gary Casey" <glcasey@adelphia.net>
All this talk about OV protection reminds me of a question I had way back
that's never been answered. It goes something like this: If we assume the
battery can be modeled by a voltage source in series with its internal
resistance the behavior should be quite simple. We're sitting there with
the battery fully charged and say I want to instantly draw 60 amps out of
the battery. The voltage should drop according to the internal resistance -
let's say it drops 1 volt. Let's instead that I suddenly push 60 amps of
current into the battery. How high does the voltage go? If the model is
correct it will rise 1 volt. As I understand batteries it will then start
to generate gas and the bubbles will increase the internal resistance,
allowing the voltage to start rising, eventually producing destructive
events. Right or wrong? Of course, the magic 60 amps of current going into
the battery is caused by a failed voltage regulator and a 60-amp alternator.
I've read comments that in the case of a sudden 60 amps going into the
battery the voltage will rise earth-destroying values in milliseconds. That
doesn't make sense to me. If that were true then a load dump from a
fully-charging alternator would also be destructive and I think a 60-amp
load dump (when connected to a good battery) will result in a very low
voltage spike, I'll bet less than 1 volt. Unfortunately, the only 60-amp
power supplies I have are not current-regulated so I can't run an experiment
on a real battery. I would like to see a voltage vs time plot of the
battery voltage when 60 amps is applied to a fully charged battery. I have
yet to see such a thing. Somehow I have trouble with the concept that you
can put 5 amps into a battery getting 13.5 volts, but at some higher current
the voltage instantly goes north, like the battery went to an open circuit.
As a side question: I ended up buying an alternator and a B&C regulator
with internal OV protection. A friend that is experienced in aerospace
reliability instantly asked, "you mean that the OV circuitry is integral
with the regulator that it is supposed to be monitoring?" I can only assume
that the OV circuitry is physically separated from the VR circuitry even
though it is in the same box?
Gary Casey
Message 5
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--> AeroElectric-List message posted by: Charlie Brame <chasb@satx.rr.com>
Slightly off topic. I have an 18v cordless screwdriver with a spare
battery. My battery charger has crapped out. More specifically, the 21v,
500ma transformer that supports the charger has gone out. Does anybody
have a source for such a transformer? Otherwise I'm looking at buying
another screwdriver just to get a charger.
Charlie Brame
RV-6A N11CB
San Antonio
Message 6
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| Subject: | Re: Using a 115 volt 400 hz device in a 12 |
--> AeroElectric-List message posted by: Matt Jurotich <mjurotich@hst.nasa.gov>
Bob
Please enlighten us. Wild frequency means?
Matthew M. Jurotich
e-mail mail to: <mjurotich@hst.nasa.gov>
phone : 301-286-5919
Message 7
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--> AeroElectric-List message posted by: "Vern W." <vernw@ev1.net>
I hope someone can steer me in a better direction with this one because I've searched
the archives, and while there's a reference or two, I don't find any definitive
answers:
To satisfy IFR requirements using both a Garmin 300XL GPS/Comm and SL-30 Nav/Comm,
I need to have an annunciator. No problem so far, but what I don't get
is that the MD41-1454 annunciator made for the 300XL costs almost $1600! I'd
like to think one of the inventive type in this group has come up with a way to
do this without spending almost half the cost of the 300XL itself.
Has anyone yet come up with a schematic to do the same thing?
Vern
Message 8
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--> AeroElectric-List message posted by: "John Danielson" <johnd@wlcwyo.com>
Look on E-bay
John L. Danielson
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
Charlie Brame
Subject: AeroElectric-List: 21V Transformer
--> AeroElectric-List message posted by: Charlie Brame
<chasb@satx.rr.com>
Slightly off topic. I have an 18v cordless screwdriver with a spare
battery. My battery charger has crapped out. More specifically, the 21v,
500ma transformer that supports the charger has gone out. Does anybody
have a source for such a transformer? Otherwise I'm looking at buying
another screwdriver just to get a charger.
Charlie Brame
RV-6A N11CB
San Antonio
Message 9
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| Subject: | Re: Using a 115 volt 400 hz device in a 12 |
--> AeroElectric-List message posted by: Jim Oke <wjoke@shaw.ca>
An AC generator/alternator that is driven by an engine that varies in speed
will provide an output that varies in frequency in some way with engine
speed. Thus the expression "wild" frequency AC. "Tame" or "fixed" frequency
AC would be carefully regulated to a particular frequency, usually 400
hertz.
Onboard AC applications such as heating prop blades or windscreens don't
much care what frequency the AC power arrives at. However, most instrument
systems do so often a separate 400 Hz inverter is installed to provide a
reliable source of "tame" AC power.
Jim Oke
Wpg., MB
RV-6A OBAM
----- Original Message -----
From: "Matt Jurotich" <mjurotich@hst.nasa.gov>
Subject: Re: AeroElectric-List: Using a 115 volt 400 hz device in a 12
> --> AeroElectric-List message posted by: Matt Jurotich
> <mjurotich@hst.nasa.gov>
>
> Bob
>
> Please enlighten us. Wild frequency means?
>
> Matthew M. Jurotich
>
> e-mail mail to: <mjurotich@hst.nasa.gov>
> phone : 301-286-5919
>
>
>
Message 10
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| Subject: | Re: Using a 115 volt 400 hz device in a 12 |
--> AeroElectric-List message posted by: Ken <klehman@albedo.net>
Bob will probably chime in with a more thorough explanation but in the
meantime this may suffice...
Heavy iron traditionally uses a constant speed drive (CSD) transmission
to keep the alternator speed and frequency constant at 400 Hz. If you
leave out the CSD and direct drive the alternator, then the frequency
will vary with engine speed and be "wild". Since a turbine usually idles
at 50% or more of full power accessory drive rpm, then the frequency
can double from idle to full power. A three phase AC motor would of
course also double its speed when the AC frequency is doubled. In some
cases designing for that, or using DC motors, is presumably
cheaper/lighter/more reliable than using a CSD.
Ken
Matt Jurotich wrote:
>--> AeroElectric-List message posted by: Matt Jurotich
<mjurotich@hst.nasa.gov>
>
>Bob
>
>Please enlighten us. Wild frequency means?
>
>Matthew M. Jurotich
>
>e-mail mail to: <mjurotich@hst.nasa.gov>
>phone : 301-286-5919
>
>
>
>
>
>
>
>
>
Message 11
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| Subject: | Re: GPS Annunciator |
--> AeroElectric-List message posted by: BobsV35B@aol.com
In a message dated 3/18/2005 9:08:12 A.M. Central Standard Time,
vernw@ev1.net writes:
To satisfy IFR requirements using both a Garmin 300XL GPS/Comm and SL-30
Nav/Comm, I need to have an annunciator.
Good Morning Vern,
I am not completely familiar with the Garmin 300XL, but for the vast
majority of IFR boxes, the need for an annunciator is dependent on the location
of
the panel unit.
If your panel unit meets the requirements for inclusion in the pilots normal
scan, no annunciator is required.
However, I totally agree with your assessment of the horrendous costs of the
annunciator units. Back when Mid Continent Instruments had some
competition, their CDIs and annunciators cost about one third of what they now
ask.
Once MCI cornered the market, their prices doubled in one stroke and have been
creeping higher ever since.
MCI is no longer one of the good guys.
Happy Skies,
Old Bob
AKA
Bob Siegfried
Ancient Aviator
Stearman N3977A
Brookeridge Airpark LL22
Downers Grove, IL 60516
630 985-8502
Message 12
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| Subject: | Re: White Paper on Crowbar OV Protection |
--> AeroElectric-List message posted by: "Matt Prather" <mprather@spro.net>
Hello Andrew,
I must have needed a good night of sleep.. I was dealing with a lot of what
seemed like dumb questions at work yesterday. Let me try this again.
From a design standpoint, an internally regulated alternator where
we don't have positive control of field current suggests the use of a B-lead
contactor. I believe field current (instead of voltage) is more important in
terms of controlling alternator output. Alternators work by magneto dynamics
as much as anything else. The field current generates a magnetic field (!).
I'll digress..
Many builders are using off-the-shelf/out-of-the-junkyard parts. They don't
have any guarantee of what the behavior of a given device will be, much less
what the internal design details are. With this in mind, to get fault
tolerance, it's
good to use a design method which makes conservative assumptions about
the performance of each device.
For instance, make an educated guess about how you think your
alternator/regulator system works. If you suspect that you won't be able to
positively control field current (Andrew's concern), design the system so
that unregulated field current won't hurt you. In this case, as has been
discussed,
the ocurrence of an overvoltage event should cause whatever installed Over
Voltage Protectection circuitry to disconnect the alternator from the bus by
opening the contacts on the B-lead relay.
If however, you are privy to the design details of a particular internal
regulator
circuit and are confident that, for instance, lowering the current through
the
control lead will tame it's output, maybe you don't need any other form of
bus
protection.
Mr Nuckolls' recent whitepaper is an analysis of the electrical performance
and behavior of a crowbar system. It talks mostly about what the voltage
and \
current on the bus are when the Crobar is thrown on the line. The whitepaper
was in response to recent discussion about these dynamics. It isn't a
treatise
on the universal applicability of such a system. I don't think it makes
an comment about what type of alternator/regulator system it is most
applicable to.
Your question is about the use of an alternator/regulator system where there
is some doubt about controlling alternator output via the systems control
lead.
In this case, a crowbar, by itself, certainly is not adequate protection
for other
devices on the bus.
I hope that helps.
Regards,
Matt-
VE N34RD, C150 N714BK
> Hi...
>
> Are you new to the list?
>
> Your questions have been discussed at length in the recent past.
>
> You have access to the easily searchable archive by clicking on one of
> the links in the bottom of the message.
>
> http://www.matronics.com/archives
>
> By the way, who are you?
>
> Regards,
>
> Matt-
> VE N34RD, C150 N714BK
>
>> --> AeroElectric-List message posted by: Andrew Rowley
>> <arowley@ncable.net.au>
>>
>> Robert L. Nuckolls, III wrote:
>>
>>> See:
>>>
>>> http://www.aeroelectric.com/articles/Crobar_OV_Protection/Crowbar_White_Paper.pdf
>>
>> I have a couple of queries...
>>
>> If I am understanding it correctly, you make the comment that the
>> alternator output is reduced when the SCR fires, because the field
>> voltage is reduced to the voltage across the SCR, about 2 volts.
>>
>> However, doesn't the internally regulated alternator supply the field
>> voltage internally, which is why reducing the (external) field voltage
>> to 0 doesn't shut off the alternator? I wouldn't be surprised if there
>> was a diode in the field supply to ensure that the alternator could
>> not supply current through the field terminal, in which case shorting
>> this circuit shouldn't have an effect on the internal field supply at
>> all.
>>
>> I would imagine that the internal field supply paths would be shorter
>> and lower resistance than the paths through the bus, so the field
>> voltage is likely to be at least as high as the bus voltage, possibly
>> higher. Do we know how much field voltage internally regulated
>> alternators actually require to produce full output? I imagine this
>> could be lower than 12V.
>>
>>
>> http://www.matronics.com/search
Message 13
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--> AeroElectric-List message posted by: "Jim Stone" <jsto1@tampabay.rr.com>
Vern,
I'm not sure why the built-in functions described in the user manual for
the 300XL wouldn't be sufficient.
http://www.garmin.com/manuals/GNC300XLTSO_PilotsGuide.pdf and search
"annunciator" seems to indicate a lot of capability.
You might want to check out "Annunciator" (AK-950) at Southeast
Aerospace. I see that Paul Lee is using one in his progect
(http://www.abri.com/sq2000/19.html). For spec's see
http://www.ameri-king.com/gps_accessories.html.
Jim Stone
Jabiru J450.
Message 14
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| Subject: | Re: GPS Annunciator |
--> AeroElectric-List message posted by: "Vern W." <vernw@ev1.net>
Jim,
An annunciator may not be needed if the 300XL is the only Nav attached
to a Nav head, but in my case, I'm going to be using the 300XL along with
the SL-30 and run them both to the GRT EFIS for Nav and HSI indication.
In this case, I'm going to have to know what signal is driving the HSI
at all times so I really do have to come up with a good annunciator.
I'm not sure, but I think Paul's installation is simpler than what I'm
doing.
Vern
----- Original Message -----
From: "Jim Stone" <jsto1@tampabay.rr.com>
Subject: RE: AeroElectric-List: GPS Annunciator
> --> AeroElectric-List message posted by: "Jim Stone"
<jsto1@tampabay.rr.com>
>
> Vern,
>
> I'm not sure why the built-in functions described in the user manual for
> the 300XL wouldn't be sufficient.
> http://www.garmin.com/manuals/GNC300XLTSO_PilotsGuide.pdf and search
> "annunciator" seems to indicate a lot of capability.
>
> You might want to check out "Annunciator" (AK-950) at Southeast
> Aerospace. I see that Paul Lee is using one in his progect
> (http://www.abri.com/sq2000/19.html). For spec's see
> http://www.ameri-king.com/gps_accessories.html.
>
> Jim Stone
> Jabiru J450.
>
>
Message 15
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| Subject: | Re: GPS Annunciator |
--> AeroElectric-List message posted by: BobsV35B@aol.com
In a message dated 3/18/2005 11:15:52 A.M. Central Standard Time,
vernw@ev1.net writes:
Jim,
An annunciator may not be needed if the 300XL is the only Nav attached
to a Nav head, but in my case, I'm going to be using the 300XL along with
the SL-30 and run them both to the GRT EFIS for Nav and HSI indication.
In this case, I'm going to have to know what signal is driving the HSI
at all times so I really do have to come up with a good annunciator.
I'm not sure, but I think Paul's installation is simpler than what I'm
doing.
Vern
Good Morning Vern,
As I said earlier, I am not familiar with that radio, but when I installed
my IFR Approach Approved Trimble 2000 Approach Plus many years ago, (which
was not mounted in my primary viewing area,) I did it all with small light
bulbs and a couple of double pole, double throw, switches. Your set may require
a resolver. That could complicate the switching, but such wiring is way over
my head.
One factor has to do with automatic switching from GPS to ILS when an ILS
frequency is selected on the "primary" navigation radio.
Such a function may be required by regulatory authorities of some countries,
but it is NOT required for aircraft used in the US National Airspace
System. Many installation shops think it is, but they are WRONG. If you want
that
capability, that is fine, but if you don't want that capability, it is not
required.
Make sure that it is what you want, not just what some installer thinks you
need.
Happy Skies,
Old Bob
AKA
Bob Siegfried
Ancient Aviator
Stearman N3977A
Brookeridge Airpark LL22
Downers Grove, IL 60516
630 985-8502
Message 16
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| Subject: | Re: GPS Annunciator |
--> AeroElectric-List message posted by: Jim Oke <wjoke@shaw.ca>
Speaking in generic terms, the reason a "separate annunciator" function is
required in a certified installation is to place an indicator of certain
modes or cautions being activated in the usual instrument scan of the pilot.
The idea is that even if the GPS box gives a plain enough RAIM or other
warning on its own display, this might go unnoticed by the pilots if the box
is far out of the normal instrument scan. If a RAIM warning light is placed,
say, just beside the ASI, it will likely be noticed by the pilot who will
then check the box and react accordingly.
The various TSOs will specify what functions must be "announced" in this
fashion. Most "certifiable" boxes will provide output circuits that will
drive the appropriate lights or whatever for this.
Jim Oke
Wpg., MB
----- Original Message -----
From: "Jim Stone" <jsto1@tampabay.rr.com>
Subject: RE: AeroElectric-List: GPS Annunciator
> --> AeroElectric-List message posted by: "Jim Stone"
> <jsto1@tampabay.rr.com>
>
> Vern,
>
> I'm not sure why the built-in functions described in the user manual for
> the 300XL wouldn't be sufficient.
> http://www.garmin.com/manuals/GNC300XLTSO_PilotsGuide.pdf and search
> "annunciator" seems to indicate a lot of capability.
>
> You might want to check out "Annunciator" (AK-950) at Southeast
> Aerospace. I see that Paul Lee is using one in his progect
> (http://www.abri.com/sq2000/19.html). For spec's see
> http://www.ameri-king.com/gps_accessories.html.
>
> Jim Stone
> Jabiru J450.
>
>
>
Message 17
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| Subject: | Re: Using a 115 volt 400 hz device in a 12 |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <b.nuckolls@cox.net>
At 10:15 AM 3/18/2005 -0500, you wrote:
>--> AeroElectric-List message posted by: Ken <klehman@albedo.net>
>
>Bob will probably chime in with a more thorough explanation but in the
>meantime this may suffice...
>
>Heavy iron traditionally uses a constant speed drive (CSD) transmission
>to keep the alternator speed and frequency constant at 400 Hz. If you
>leave out the CSD and direct drive the alternator, then the frequency
>will vary with engine speed and be "wild". Since a turbine usually idles
>at 50% or more of full power accessory drive rpm, then the frequency
>can double from idle to full power. A three phase AC motor would of
>course also double its speed when the AC frequency is doubled. In some
>cases designing for that, or using DC motors, is presumably
>cheaper/lighter/more reliable than using a CSD.
>Ken
Dead on Ken. The alternators on the B-52 in 1960 had
constant speed drives to maintain 400 Hz from the
alternators over full operating range of engine RPM.
These are basically hydraulic pumps driving hydraulic
motors of the wobble plate variety. A governor attached
to the wobble plates maintains fluid flow from
pump to motor such that output RPM was constant irrespective
of engine RPM.
A few years hence, someone decided that we could eliminate
an expensive heavy drive system if devices requiring AC
power could be made to accept a wider range of frequencies.
Transformers can be designed with 400Hz windings and core
magnetics but fabricated from 1000Hz materials with respect
to losses and guess what? The thing runs fine over range
of 400-1000 Hz.
This is the philosophy of choice for new systems design
and has been in place now for perhaps 20 years or more.
Bob . . .
Message 18
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| Subject: | Re: White Paper on Crowbar OV Protection |
--> AeroElectric-List message posted by: Andrew Rowley <arowley@ncable.net.au>
BobsV35B@aol.com wrote:
> That is very nice to know, but we have still not seen a name.
>
> The convention on this list seems to be to sign your message with a name,
> your type or style of aircraft and your location, often the airport from
> which you fly.
>
> We are a nosy bunch.
> And; Welcome Aboard!
Thanks, as I said my sig went missing, and I had not realised it was
gone. The original "who are you" was a little subtle for me :-) It's
under control now.
I should be adding:
do not archive
too.
--
Andrew Rowley
arowley@ncable.net.au
Message 19
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| Subject: | Re: White Paper on Crowbar OV Protection |
--> AeroElectric-List message posted by: Andrew Rowley <arowley@ncable.net.au>
Matt Prather wrote:
> Mr Nuckolls' recent whitepaper is an analysis of the electrical performance
> and behavior of a crowbar system. It talks mostly about what the voltage
> and \
> current on the bus are when the Crobar is thrown on the line. The whitepaper
> was in response to recent discussion about these dynamics. It isn't a
> treatise
> on the universal applicability of such a system. I don't think it makes
> an comment about what type of alternator/regulator system it is most
> applicable to.
>
> Your question is about the use of an alternator/regulator system where there
> is some doubt about controlling alternator output via the systems control
> lead.
> In this case, a crowbar, by itself, certainly is not adequate protection
> for other
> devices on the bus.
>
> I hope that helps.
Hi Matt,
Actually, my question was intended to be a lot more specific than that.
I think Paul Messinger raised concerns about a load dump damaging
regulators when the contacter is opened on the "B" lead, because the
crowbar short drives the alternator to full output before the contacter
opens.
In the whitepaper, Bob said
"If one uses a crowbar OV module in combination with an internally
regulated alternator, field supply to the alternator is choked off at
the 2 volt level as soon as the SCR fires . . . the alternator is
already starved for field current long before the breaker opens."
My question is: "Is that really true?" I can see how that would be the
case for an externally regulated alternator, but I am not convinced that
dropping the field voltage to 2 volts would do anything to reduce the
output from an internally regualted alternator - which is the original
problem.
I have no doubt the crowbar would protect the rest of the devices on the
bus, but the concern is what could it do to the regulator if you open
the B lead when the alternator is producing maximum output.
I have some similar concerns about the system I will have on my Rotax,
as the suggested design for that also has a contacter on the output
lead, although (correct me if I'm wrong) I don't think the PM
alternators have the same problem with load dump because they don't
control the magnetic field.
--
Andrew Rowley
arowley@ncable.net.au
Message 20
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| Subject: | headset level to mic level for recording |
--> AeroElectric-List message posted by: "Dan Checkoway" <dan@rvproject.com>
I'm not even sure if it's called a "pad" but I think it is... Here's the
deal. I bought a digital voice recorder thing from Radio Smack with the
intention of recording intercom & radio activity in the plane. The recorder
has an 1/8" mic jack, and it has two "sensitivity" settings, hi and lo. I
connected the passenger headset jack to the mic jack on the recorder, and
not surprisingly the recorder is slightly overloaded level-wise.
I recall seeing an XLR device called a "pad" which allows you to select
impedance or something to that effect.
Is there a simple way to drop/adjust the headset jack output level to be
suitable as "mic level"? I found this via Google:
http://www.hut.fi/Misc/Electronics/circuits/line_to_mic.html
...but I think that applies to line level, not headset level. Maybe
somebody can set me straight and provide some "for dummies" instruction on
this.
Thanks in advance,
)_( Dan
RV-7 N714D
http://www.rvproject.com
Message 21
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| Subject: | Re: White Paper on Crowbar OV Protection |
--> AeroElectric-List message posted by: "Matt Prather" <mprather@spro.net>
Ah, I see what you are getting at.
Some internally regulated alternators source their field current through
internal pathways and some source it from the control lead. What Mr.
Nuckolls says is true for an internally regulated alternator which gets
its field current through the control lead.
For the other style, when the SCR fires, it holds the bus voltage down to
around 11V until the breaker opens, at which point the B-lead contactor
opens. As the article says, the contactor may stay closed until breaker
opens - dropping only to 2 or so volts. But, the opening time of the
contactor is much faster then when at 13volts. At this point, the only
thing that might be dangerous is that the internal regulator or field winding
overheats itself with 100% field current. Probably a very small risk of
fire
there. My 'guess' is that alternators are designed to reach their rated
output at 100% field current. Anybody care to comment on that? If so, the
alternator shouldn't overheat.
Regards,
Matt-
> --> AeroElectric-List message posted by: Andrew Rowley
> <arowley@ncable.net.au>
>
> Matt Prather wrote:
>
>> Mr Nuckolls' recent whitepaper is an analysis of the electrical
>> performance and behavior of a crowbar system. It talks mostly about
>> what the voltage and \
>> current on the bus are when the Crobar is thrown on the line. The
>> whitepaper was in response to recent discussion about these dynamics.
>> It isn't a treatise
>> on the universal applicability of such a system. I don't think it
>> makes an comment about what type of alternator/regulator system it is
>> most applicable to.
>>
>> Your question is about the use of an alternator/regulator system where
>> there is some doubt about controlling alternator output via the
>> systems control lead.
>> In this case, a crowbar, by itself, certainly is not adequate
>> protection for other
>> devices on the bus.
>>
>> I hope that helps.
>
> Hi Matt,
>
> Actually, my question was intended to be a lot more specific than that.
> I think Paul Messinger raised concerns about a load dump damaging
> regulators when the contacter is opened on the "B" lead, because the
> crowbar short drives the alternator to full output before the contacter
> opens.
>
> In the whitepaper, Bob said
> "If one uses a crowbar OV module in combination with an internally
> regulated alternator, field supply to the alternator is choked off at
> the 2 volt level as soon as the SCR fires . . . the alternator is
> already starved for field current long before the breaker opens."
>
> My question is: "Is that really true?" I can see how that would be the
> case for an externally regulated alternator, but I am not convinced that
> dropping the field voltage to 2 volts would do anything to reduce the
> output from an internally regualted alternator - which is the original
> problem.
>
> I have no doubt the crowbar would protect the rest of the devices on the
> bus, but the concern is what could it do to the regulator if you open
> the B lead when the alternator is producing maximum output.
>
> I have some similar concerns about the system I will have on my Rotax,
> as the suggested design for that also has a contacter on the output
> lead, although (correct me if I'm wrong) I don't think the PM
> alternators have the same problem with load dump because they don't
> control the magnetic field.
>
> --
> Andrew Rowley
> arowley@ncable.net.au
>
>
Message 22
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| Subject: | Re: headset level to mic level for recording |
--> AeroElectric-List message posted by: rv-9a-online <rv-9a-online@telus.net>
Dan, the link you provided shows the correct way to attenuate the
signal. The resistor values may need to be adjusted, but the app note
is a good starting point. If you don't want to hardwire it into your
airplane, you can build it externally and wrap it in heat shrink. You'd
need to make a cable with a jack and a plug as well, so that you can
insert your gizmo in series with your recorder.
You could also use a volume control potentiometer in place of the two
resistors, (10K pot would work) and have total control on the levels.
The volume control will have three leads: connect one outside lead to
your headphone plug (tip), the other outside lead to headphone plug
ground (sleeve). Then connect the middle lead and ground to the
miniature audio jack.
I hope this helps.
Vern Little, RV-9A.
And thanks for the great website!
Dan Checkoway wrote:
>--> AeroElectric-List message posted by: "Dan Checkoway" <dan@rvproject.com>
>
>I'm not even sure if it's called a "pad" but I think it is... Here's the
>deal. I bought a digital voice recorder thing from Radio Smack with the
>intention of recording intercom & radio activity in the plane. The recorder
>has an 1/8" mic jack, and it has two "sensitivity" settings, hi and lo. I
>connected the passenger headset jack to the mic jack on the recorder, and
>not surprisingly the recorder is slightly overloaded level-wise.
>
>I recall seeing an XLR device called a "pad" which allows you to select
>impedance or something to that effect.
>
>Is there a simple way to drop/adjust the headset jack output level to be
>suitable as "mic level"? I found this via Google:
>
>http://www.hut.fi/Misc/Electronics/circuits/line_to_mic.html
>
>...but I think that applies to line level, not headset level. Maybe
>somebody can set me straight and provide some "for dummies" instruction on
>this.
>
>Thanks in advance,
>)_( Dan
>RV-7 N714D
>http://www.rvproject.com
>
>
>
>
--
No virus found in this outgoing message.
Checked by AVG Anti-Virus.
Message 23
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| Subject: | Re: White Paper on Crowbar OV Protection |
--> AeroElectric-List message posted by: Andrew Rowley <arowley@ncable.net.au>
Matt Prather wrote:
> --> AeroElectric-List message posted by: "Matt Prather"
<mprather@spro.net>
>
> Ah, I see what you are getting at.
>
> Some internally regulated alternators source their field current through
> internal pathways and some source it from the control lead. What Mr.
> Nuckolls says is true for an internally regulated alternator which gets
> its field current through the control lead.
>
> For the other style, when the SCR fires, it holds the bus voltage down to
> around 11V until the breaker opens, at which point the B-lead contactor
> opens. As the article says, the contactor may stay closed until breaker
> opens - dropping only to 2 or so volts. But, the opening time of the
> contactor is much faster then when at 13volts. At this point, the only
> thing that might be dangerous is that the internal regulator or field
winding
> overheats itself with 100% field current. Probably a very small risk of
> fire
> there. My 'guess' is that alternators are designed to reach their rated
> output at 100% field current. Anybody care to comment on that? If
so, the
> alternator shouldn't overheat.
I wouldn't be worried about the alternator overheating. The problem that
has been described is Vans alternators failing on systems where the OVP
is installed. The question then is how might the OVP do something that
damages the alternator (actually most likely the regulator I think).
Would I be right in assuming that if the alternator sources field
current through the control lead, the traditional method of turning off
the control lead would shut off the alternator, and cutting the B lead
is not necessary? So when we discuss opening the B lead contactor, we
are talking about systems that do not source field current through the
control lead?
If I understand correctly, Paul is saying that opening the B lead
produces a load dump event which is effectively internal to the
alternator, and doesn't even have a battery connected any more to absorb
it. This then may damage components in the alternator due to overvoltage.
However, as I said in a different message, if you can't turn the
alternator off by the control lead, and you want to be able to shut off
the alternator, I don't see much alternative other than disconnecting
the "B" lead.
--
Andrew Rowley
arowley@ncable.net.au
Message 24
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| Subject: | Re: Points for discussion OVP//more |
--> AeroElectric-List message posted by: "Paul Messinger" <paulm@olypen.com>
Its not the same and more like what Bob recommends.
I have gotten back and will be responding to all the commenst in one way or
the other soon.
Paul
There is more to life than this list :-)
----- Original Message -----
From: "John Swartout" <jgswartout@earthlink.net>
Subject: RE: AeroElectric-List: Points for discussion OVP//more
> --> AeroElectric-List message posted by: "John Swartout"
> <jgswartout@earthlink.net>
>
> Paul, thanks for being patient with me and others on this list who are
> neophytes. Trying to follow along, learn something, and build a better
> airplane.
>
> Is the system you describe below approximately the same thing as the
> Zeftronics-built ASP101 Overvoltage protection sold by Niagara Airparts
> (described and schematicized here:
> http://www.niagaraairparts.com/ASP101-PIT%201.pdf), except that you add
> the transorbs?
>
> Thanks.
>
> John
>
> -----Original Message-----
> From: owner-aeroelectric-list-server@matronics.com
> [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Paul
> Messinger
> To: aeroelectric-list@matronics.com
> Subject: Re: AeroElectric-List: Points for discussion OVP//more
>
> --> AeroElectric-List message posted by: "Paul Messinger"
> <paulm@olypen.com>
>
>
> Use the proper size fuse in the "B" lead. I suggest that a 55 amp
> alternator
> should use a 60 amp as that fuse is designed to run forever at 60 amps
> and
> hopefully your load will hardly ever approach 55 amps. A failed and
> shorted
> alternator will supply more than rated current but lets not over due it.
>
> Use a OVP that opens the alternator field circuit. The 16.2V setting is
> fine. Eric Jones has this as a stock item. Please do not use a shorting
> crowbar here as that is cruel and unusual punishment to the electrons.
>
> Put a parallel set of 16V transorbs across the system bus between the
> fuse
> and the bus. The transorbs will clamp the bus to under 20V and blow the
> fuse
> if the failure is a real (quite rare)failure of the alternator that the
> field lead cannot control. Normally the field OVP will trip (having a
> 200 ms
> delay for load dump transients) and correct the problem. If this fails
> the
> transorbs will clamp the bus to a safe level and blow the fuse. The
> number
> of transorbs is under investigation (6-10 max expected worst case) but
> they
> are low cost ($0.41 each) in small quantities and Mouser has them in
> stock
> at this time.
>
> Look for 1N6276A or 1.5KE16A they are the same part functionally.
>
> The KISS principal wins another battle.
>
> Paul
>
>
>
Message 25
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| Subject: | Re: Points for discussion OVP//more |
--> AeroElectric-List message posted by: "Paul Messinger" <paulm@olypen.com>
Embedded comments after snipping for brevity.
----- Original Message -----
From: "Robert L. Nuckolls, III" <b.nuckolls@cox.net>
Subject: Re: AeroElectric-List: Points for discussion OVP//more
> --> AeroElectric-List message posted by: "Robert L. Nuckolls, III"
> <b.nuckolls@cox.net>
>
> At 01:35 PM 3/14/2005 -0800, you wrote:
>
>>--> AeroElectric-List message posted by: "Paul Messinger"
>><paulm@olypen.com>
>>Use a hi quality ND rebuild alternator and / or a new one. One with a hi
>>quality regulator that controls the field all the time.
>
> I've wrestled with this issue for years. The term "high quality"
> is simply not quantifiable.
It is around here if you know what auto parts dealer to go to.
I go in and ask for a part and the reply is what quality level do you want?
The usual brand of parts makes 2 or 3 quality levels normal good and high.
This independent auto store with mechanics for salesmen are great. The store
will order the normal quality level if you insist but do not stock this
level as there have been too many returns.
The good quality is what is stocked and one needs to special order the High
quality.
Take the GM HEI control module I use in hundreds of dual ign systems for
Subaru engines. Only the Hi quality is flight proven to last. lower quality
levels fail.
Or take the external "ford" alternator regulator. Only the High quality unit
has OVP built in and flashes the "idiot light in case of alternator failure.
Typical pricing might be 20 for normal, 40 for good and 75 for High quality
levels.
Many do not know this variability of parts quality exist either because they
deal with a major chain or the sales staff do not know about it.
I have de-lidded etc the different quality levels and there is a significant
difference in design and parts quality. You get what you pay for.
>
>>Use the proper size fuse in the "B" lead. I suggest that a 55 amp
>>alternator
>>should use a 60 amp as that fuse is designed to run forever at 60 amps and
>>hopefully your load will hardly ever approach 55 amps. A failed and
>>shorted
>>alternator will supply more than rated current but lets not over due it.
>
> How so? For several years we used to supply JJN- and JJS series
> fuses for alternator b-lead protection. A 60-amp fuse was offered
> for both 40 and 60 amp alternators. Several years into the activity,
> folks started complaining about popping the 60A fuse on an L-60
> installation.
>
> After some invstigation we found that the fuses popped when
> the owner tried to charge a dead battery by running the engine.
> The cold L-60 would easily open a 60A fast fuse.
This was a lets see what Bob would say. Do you have any real data that
states the maximum output of any 55 amp alternator when supplied with 14V DC
to the field and is turning at 8,000 rpms?
I do not but you have often said the max out put is only slightly higher
than rated.
I now have a 500 amp load tester and will be testing the more or less ND
alternator in the next few weeks. We will see what it can produce. However
every brand and style may have different max currents. My testing to date
suggests that the max output will be much greater under a full dc
application of field voltage.
>
>>Use a OVP that opens the alternator field circuit. The 16.2V setting is
>>fine. Eric Jones has this as a stock item. Please do not use a shorting
>>crowbar here as that is cruel and unusual punishment to the electrons.
>
> "Cruel and unusual" is not quantified.
lighten up its supposed to be funny!
Went to the bench this afternoon
> and duplicated some work I did at Electro-Mech about 25 years ago.
> See white paper report at:
>
> http://www.aeroelectric.com/articles/Crobar_OV_Protection/Crowbar_White_Paper.pdf
I have extensive comments on this in a soon to be posted review!
>
> If you set the voltage regulator for 16.3 volts with the transorbs
> in place, will they take the system off line?
No and what is magic about any voltage above 15.5 and below 16.5??? It seems
to me that 16V was picked as high enough to be easy to reliability set with
the parts available years ago. Today there is no reason for a wide voltage
margin of safety. Of course the OVP must not have a hair trigger and false
trip from load dumps or contactor contact bounce induced spikes (yes I have
captured on film the elusive "snipe" Perhaps private joke between us Bob :-)
I would set a OVP at 15.50-15.75V trip only after 200ms. The OVP would only
OPEN the "B" lead and do it using a fet not a huge contactor etc. The
transorbs are there for load dumps, transients, and if one wanted to
continue flight with a battery system failure etc. More on this soon.
Paul
Message 26
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| Subject: | Re: Alternator Control |
--> AeroElectric-List message posted by: "Paul Messinger" <paulm@olypen.com>
As I have stated there are different "qualities" of ND alternator rebuilds
and older ones have on occasion been the type where field control was lost
once they were turned on.
Vans regulators are different from yours as field control is always
externally controlled unless there is an internal failure of the regulator.
Modern regulators are much less likely to have hard failures internally with
the advent of modern autos and the extensive electronics installed.
A brand new alternator for an older auto may have the older style of
regulator as the auto wiring may expect the old once on always on type of
control. Thus there is a danger of any new or rebuilt alternator sold for an
older auto containing the modern internal regulator. I am unwilling to
guess.
Can you share with us what happened and what was the source of your failed
alternator?
Paul
----- Original Message -----
From: "Richard Garforth" <richard@hawk.flyer.co.uk>
Subject: AeroElectric-List: Alternator Control
> --> AeroElectric-List message posted by: "Richard Garforth"
> <richard@hawk.flyer.co.uk>
>
> Paul,
>
> Having just had a real long and bad experience with ND internally
> regulated alternators (without OV protection). I am curious about your
> statement that suggests you can turn off the alternator via the 'field
> control' lead. My experience has been you can initiate o/p by applying
> +12v to the 'field' lead but subsequent removal of the 12 volts leaves the
> alt churning out amps. Have the alternators supplied by VANS (60 amp ND) a
> different regulator ?
>
> Richard ( a convert to B&C )
>
Message 27
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| Subject: | Re: White Paper on Crowbar OV Protection |
--> AeroElectric-List message posted by: "Matt Prather" <mprather@spro.net>
Huh.. I think we are going in circles here.. I went back to the archive and
re-read one of your earlier posts.
"If a device that simply opens the B lead is enough to damage the
alternator, it doesn't sound like the real reason is the OVP module
(although it is possible it could make a problem more likely). It
suggests to me that these alternators should not be disconnected at all
once running, and if you want the ability to do that maybe they are not
suitable. Of the thousands of aircraft flying without failures, how many
have tested what happens if the alternator is disconnected?"
I agree. The alternators that Van's sells probably are ones which
don't source the field current through the sense wire. They are probably
automotive derivative and as such, running without a battery wasn't one of
the design parameters.
Operationally, the risk of damage from a disconnect can probably be
minimized. Take actions which disconnect the b-lead only when the
loads and possible output are low. Don't cycle the alternator on a cold
night when all the lights are on and the engine is turning cruise RPM.
Whether an alternator which supplies its field current through the control
wire should be installed with a b-lead contactor is debatable. If I use an
alternator that has internal regulator, it will have the contactor. I
don't know
what the fail modes in the regulator are.. Is there another path for
excitation
to get through?
Regards,
Matt-
VE N34RD, C150 N714BK
> --> AeroElectric-List message posted by: Andrew Rowley
> <arowley@ncable.net.au>
>
> Matt Prather wrote:
>
> > --> AeroElectric-List message posted by: "Matt Prather"
> <mprather@spro.net>
> >
> > Ah, I see what you are getting at.
> >
> > Some internally regulated alternators source their field current
> through internal pathways and some source it from the control lead.
> What Mr. Nuckolls says is true for an internally regulated alternator
> which gets its field current through the control lead.
> >
> > For the other style, when the SCR fires, it holds the bus voltage
> down to around 11V until the breaker opens, at which point the B-lead
> contactor opens. As the article says, the contactor may stay closed
> until breaker opens - dropping only to 2 or so volts. But, the
> opening time of the contactor is much faster then when at 13volts.
> At this point, the only thing that might be dangerous is that the
> internal regulator or field
> winding
> > overheats itself with 100% field current. Probably a very small
> risk of fire
> > there. My 'guess' is that alternators are designed to reach their
> rated output at 100% field current. Anybody care to comment on that?
> If
> so, the
> > alternator shouldn't overheat.
>
> I wouldn't be worried about the alternator overheating. The problem that
> has been described is Vans alternators failing on systems where the OVP
> is installed. The question then is how might the OVP do something that
> damages the alternator (actually most likely the regulator I think).
>
> Would I be right in assuming that if the alternator sources field
> current through the control lead, the traditional method of turning off
> the control lead would shut off the alternator, and cutting the B lead
> is not necessary? So when we discuss opening the B lead contactor, we
> are talking about systems that do not source field current through the
> control lead?
>
> If I understand correctly, Paul is saying that opening the B lead
> produces a load dump event which is effectively internal to the
> alternator, and doesn't even have a battery connected any more to absorb
> it. This then may damage components in the alternator due to
> overvoltage.
>
> However, as I said in a different message, if you can't turn the
> alternator off by the control lead, and you want to be able to shut off
> the alternator, I don't see much alternative other than disconnecting
> the "B" lead.
>
> --
> Andrew Rowley
> arowley@ncable.net.au
>
>
Message 28
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| Subject: | Re: White Paper on Crowbar OV Protection |
--> AeroElectric-List message posted by: "Paul Messinger" <paulm@olypen.com>
If the internal regulator gets all its power from the field lead then
opening this lead stops the alternator output current. I have modified
several brands to eliminate the internal "B" lead to regulator connection
and then the only "B" lead protection is a fuse. Not easy to do on ND brand.
GOOD alternator internal regulators have adequate load dump protection built
in. Why Vans fail when coupled with OVP and not just Bobs is a mystery at
present. Vans has no answer.
However its not necessary to disconnect the "B" lead when the alternator is
running except in a failure mode. It should never be done as a matter of
testing in my opinion.
Paul
----- Original Message -----
From: "Matt Prather" <mprather@spro.net>
Subject: Re: AeroElectric-List: White Paper on Crowbar OV Protection
> --> AeroElectric-List message posted by: "Matt Prather"
> <mprather@spro.net>
>
> Huh.. I think we are going in circles here.. I went back to the archive
> and
> re-read one of your earlier posts.
>
> "If a device that simply opens the B lead is enough to damage the
> alternator, it doesn't sound like the real reason is the OVP module
> (although it is possible it could make a problem more likely). It
> suggests to me that these alternators should not be disconnected at all
> once running, and if you want the ability to do that maybe they are not
> suitable. Of the thousands of aircraft flying without failures, how many
> have tested what happens if the alternator is disconnected?"
>
> I agree. The alternators that Van's sells probably are ones which
> don't source the field current through the sense wire. They are probably
> automotive derivative and as such, running without a battery wasn't one of
> the design parameters.
>
> Operationally, the risk of damage from a disconnect can probably be
> minimized. Take actions which disconnect the b-lead only when the
> loads and possible output are low. Don't cycle the alternator on a cold
> night when all the lights are on and the engine is turning cruise RPM.
>
> Whether an alternator which supplies its field current through the control
> wire should be installed with a b-lead contactor is debatable. If I use
> an
> alternator that has internal regulator, it will have the contactor. I
> don't know
> what the fail modes in the regulator are.. Is there another path for
> excitation
> to get through?
>
> Regards,
>
> Matt-
> VE N34RD, C150 N714BK
Message 29
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| Subject: | Re: Using a 115 volt 400 hz device in a 12 |
--> AeroElectric-List message posted by: Jerzy Krasinski <krasinski@provalue.net>
>
> A few years hence, someone decided that we could eliminate
> an expensive heavy drive system if devices requiring AC
> power could be made to accept a wider range of frequencies.
> Transformers can be designed with 400Hz windings and core
> magnetics but fabricated from 1000Hz materials with respect
> to losses and guess what? The thing runs fine over range
> of 400-1000 Hz.
>
> This is the philosophy of choice for new systems design
> and has been in place now for perhaps 20 years or more.
>
> Bob . . .
>
>
>
Bob,
Just for curiosity, what frequency is generated by alternator (before
rectification) in a typical Cessna in cruise conditions?
Jerzy
Message 30
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| Subject: | Re: OV protection debate |
--> AeroElectric-List message posted by: "Paul Messinger" <paulm@olypen.com>
I did testing that included all you seem to want in the Load Dump study.
I setup a simple but complete electrical system (using real sized wiring and
gauges) from battery to running alternator. For the OVP testing I tested 3
different CB styles from 2 mfgrs to verify the data.
I have several hundred photos and many pages of test results that are on the
slow path to being on my web site.
However there is a fundamental difference of opinion in how to control load
dump and more important how to stop a runaway alternator in the modern
aircraft with modern avionics.
Eric Jones and I have designed and tested a method of OVP protection that
eliminates any large current surges and spikes before and after the Crowbar
approach. The crow bar approach takes a few milliseconds to start clamping
and after its opens the cb there may remain a large spike that comes from
the alternator before the "B" lead contactor finally opens.
I have taken a lot of heat from Eric on publishing the complete report but I
have so little time and so much to do. Eventually is what #2 priority gets
:-) If one only publishes parts there are unanswered questions that remain.
Also I dislike to report in pure engineering terms as there are so few that
would understand what I am saying and so many that need to hear it in
general english.
Paul
----- Original Message -----
From: "Tim Olson" <Tim@MyRV10.com>
Subject: Re: AeroElectric-List: OV protection debate
> --> AeroElectric-List message posted by: Tim Olson <Tim@MyRV10.com>
>
> Would it maybe not help solve some of this debate as to the OV
> protection if perhaps Eric, Paul, and Bob all drew up their
> favorite OV protection circuit, and maybe one or all of them
> took the time to actually run them and produce a situation
> that would cause trouble? I know Bob ran his circuit to
> prove his....but I'd be interested to see a couple of different
> OV options, and graphs of voltage and current spikes that
> happened when an OV condition was created. It seems like
> all of this debating back and forth could be settled
> with just a few hours of directly compared experiments...
>
> Tim
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