Today's Message Index:
----------------------
1. 11:01 AM - Re: Battery Dumps (Robert L. Nuckolls, III)
2. 12:17 PM - Re: Battery dumps (Robert L. Nuckolls, III)
3. 12:22 PM - Re: Figure Z-14 and Battery-Dump (Robert L. Nuckolls, III)
4. 03:52 PM - loadmeters (Tom Barter)
5. 06:51 PM - Help with Diagnosis (Matt Jurotich)
6. 07:12 PM - Weird LED fuse behavior (John Slade)
7. 09:04 PM - Fw: Transponder arial location (Rick Fogerson)
8. 10:04 PM - Re: Re: Battery dumps (Paul Messinger)
9. 11:13 PM - ?B lead to contactor or to battery? (Troy Scott)
Message 1
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| Subject: | RE: Battery Dumps |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
At 04:39 PM 2/27/2004 -0500, you wrote:
>--> AeroElectric-List message posted by: "Rogers, Bob J." <BRogers@fdic.gov>
>
>I plan to have an internally regulated 80-amp alternator (from a Mazda RX-7)
>as my primary electrical energy source, with a second 35-amp permanent
>magnet internally regulated alternator as a back up source of electricity.
>I will have only one battery.
>
>I need to be able to test the back-up alternator before I fly, which
>involves turning at least one alternator off while the engine is running (or
>switching from one alternator to the other). What is the correct procedure
>to insure that I do not accidentally destroy an alternator or any other
>electrical component of my system?
The PM alternator is not subject to the phenomenon of
battery-dump spiking. If you have alternator loadmeter
shunts in the output of both alternators, they'll
allow you to monitor individual alternator behavior
during preflight. A low voltage warning light is your
primary first notification of a tired or broken alternator
and will suffice for preflight checks of dual alternators.
Start the engine and turn the PM alternator on first.
Observe that you have output current. If loadmeters are
not installed, observe that your low voltage warning light goes
out when the alternator comes on. Turn the PM alternator
off and the main alternator on. Loadmeter should show
output and the low voltage light should stay off.
There's no operational need for turning the main
alternator off again until time to park the airplane.
At that time system loads should be minimal, the
battery charged and the engine is at idle rpm. Battery
dumps of damaging proportions don't happen under
these conditions.
By the way, I've been making some effort to re-label
the phenomenon under discussion "battery dump"
as opposed to "load dump". In aviation, "load dump"
speaks clearly to the phenomenon excited by
relieving the SYSTEM of a heavy load like hydraulic
pump, windshield heater, etc. We EXPECT to see
system voltage perturbations but in the general
sense, "load dump" is from a system perspective
wherein a battery is a component of stabilizing
influences.
Not trying to be obtuse . . . if I use the
phrase "load dump" during conversation with
my associates in spam-can-land, the image that
pops into their thoughts does not describe what
we're talking about here. The more precise and
less familiar term "battery dump" allows me
to answer their questioning response with a
description brings understanding about a
condition that is seldom (if ever) considered.
Bob . . .
Message 2
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| Subject: | Re: Battery dumps |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
At 01:21 PM 2/27/2004 -0800, you wrote:
>--> AeroElectric-List message posted by: "Paul Messinger" <paulm@olypen.com>
>
>---- Original Message -----
>From: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
>To: <aeroelectric-list@matronics.com>
>Subject: Re: AeroElectric-List: Re: Load Dumps
>
>
> > --> AeroElectric-List message posted by: "Robert L. Nuckolls, III"
><bob.nuckolls@cox.net>
>
> > The big question is how the alternator's built in regulator behaves.
> > If the regulator can open the field circuit before voltages get
> > so high that the regulator itself is damaged, then everything
> > comes to rest in an orderly manner. Depending on response time
> > of the REGULATOR, the TVS has to grunt 50A or so of current for
> > DURATION OF RESPONSE TIME . . . this is how George's TVS got
> > launched into orbit.
> >
> > Response time can be a huge variable from one make of regulator
> > to the next. I'm hoping that we can deduce enough information
> > from the testing to modify recommendations for implementing
> > Z-24 with some degree of comfort. If not (and the pilot
> > really feels a need to flip alternator switches on and off
> > while the engine is running), then I may have to retreat
> > to the original philosophy of recommending that airplanes
> > fly only with externally regulated alternators.
>
>I do not see how there is any basic difference (with regard to LOAD DUMP)in
>internally regulated VS externally regulated Alternators;
The "problem" we're addressing is the fact that some
alternators with built in regulators will shoot themselves
between the eyes if the pilot switches them on/off in Figure
Z-24 with the engine running and with the alternator carrying
some significant load. This generates something akin to
the automotive "load dump" except that effects are
limited to the alternator itself.
Both styles of alternator can be goaded into producing
a battery-dump surge of output voltage, but for everything
except Z-24 wiring this has been a rare event and very
low on the list of concerns. Many more radios have been smoked
for lack of ov protection than for any other reason. Experience
indicates (and DO-160 infers) that once this dragon is adequately
chained down, probability of letting lots of smoke out of your
radios is very low.
<snip>
>Either way the TVS current is limited to a few ms and can be tolerated by
>the proper TVS. however the TVS may allow a few ms of relatively HV to
>appear on the main buss that can exceed the equipment ratings.
Only if the equipment is not designed to live in the real
world of airplanes (or any other vehicle with a DC power
generation system).
>Mostly agree on Z-24, however, protection from pilot is only part of the
>concern. I really do not like the use of procedures to prevent equipment
>damage. Throwing the incorrect switch should never cause damage!
It's not a procedure . . . it's a rational/natural mode of
operating the airplane. One should not apply rapid full
travel of flight controls above certain published airspeeds . . .
okay as far as procedures go but I've never had occasion or
desire to exercise it. By the same token, I cannot recall a
single time I felt a need to cycle alternator and/or battery
switches for anything other than troubleshooting on the ground
or in the normal course of turning things on during preflight
and turning things off before I park the airplane.
Even then the alternator always goes off first and does NOT have
an internal regulator. You can take ANY certified single with
the infamous split rocker master switch and punch the alternator
and battery off simultaneously by hitting both sides of the
switch. This simultaneously disconnects the battery AND the
alternator field . . . the mechanically linked nature
of the split-rocker COMBINED with the fact that all spam-cans
have externally regulated alternators makes this action a non-
event with respect to battery dump.
>I am addressing a different case. First, not everyone has your progressive
>switches;
Can't help it if the reasoning behind the use of
progressive master switches is misunderstood or ignored.
The split rocker was crafted to address these issues
45 years ago . . . and aside from the fact that it
mounts in a square cornered hole and looks nothing
like the other switches in the panel, there's nothing
"wrong" with the split rocker. It's made by Carling
and has the same guts behind the panel as the 2-10
toggle switch. The spirit and intent of this switch
has stood the test of time quite well even if the
switch itself has been root cause of many unnecessary
replacements for alternators and regulators in spam-cans.
The Z-figures have shown either simultaneous or progressive
disconnection of alternator/battery since day-one. If
someone chooses to wire their airplane like a Bonanza,
well . . .
> and you do not seem to address contactor failure. (however
>unlikely its not zero).
Contactor failure, particularly contactor failure while the
battery presents a substantial portion of the total alternator
load is very rare.
> The importance of your progressive switch as the key
>to your above statement should be included.
>Failure of one device should never cause additional failures. I suggest that
>a battery contactor failure should not result in a load dump where the
>alternator is still connected to the main bus. Regardless of the potential
>damage of the alternator regulator the main bus gets the impact of the load
>dump and prtection needs to be added in my opinion.
The combination of DO-160 qualification and designing electrical
systems constrained to Mil-STD-704 has a pretty good track record
for covering all the bases . . . including battery-dump. If one
chooses to install accessories which are less robust, then there
are certainly new issues to be considered.
>My testing to date has shown to me that the remaining issue is the peak
>voltage and duration during the TVS protected load dump VS the ability of
>the equipment to tolerate that transient.
Can you share a repeatable experiments for the tests and the
data derived therefrom? We've been hashing this topic for
several weeks now but I've yet to see hard data by which
one can make rational recommendations for either part
selection or places where it's a good thing to include
as part of the system design.
Everyone is free to stack as many "firewalls" against the
extraordinary and unexpected as they wish. I try to avoid
recommendations for firewalls in favor of designing the risks
out (which is, in part, what DO-160 is about). I'll be pleased
to have some real hammer-n-tongs data for color and size of the
beast. It will be nice if there's a practical, one-part
solution with sufficient stature to provide a 99% plus
probability for standing off a battery dump event.
It is my intention to document testing along with a rational for
part selection which we'll recommend as an important inclusion
to Figure Z-24. We'll add information specific to this
topic at the next revision to the OV protection chapter
in the 'Connection. Of course, folks are welcome to apply
the technique to any other configuration as they see fit.
As for as my recommendations . . . may I suggest it's hard
to beat Figure Z-11 with a B&C L-40/LR-3 combination that
drives accessories capable of standing off DO-160 defined
stresses WITH or WITHOUT battery dump protection.
This combination of B&C products has amassed something on order
of a million flight hours of experience over the last 15 years.
This represents a whole lot of pilots who have had very few
reasons to worry their electrical systems. I'm confident
that we'll be able to bring a similar level of confidence
to the use of internally regulated alternators but
not until the NUMBERS are known and describe in a way
that anyone else can go verify/confirm as they see fit.
Bob . . .
Message 3
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| Subject: | Re: Figure Z-14 and Battery-Dump |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
>Comments/Questions: I have installed a dual alt / dual bus system in my RV
>per your design. Is there a failure mode which would make use of the
>X-Feed switch unwise? If so, how do I identify that failure mode prior to
>using the x-feed?
If you have internally regulated alternators and you've
wired with progressive (2-10) or simultaneous (2-3) switching
of alternator/battery in the Master DC power control switches,
there are no combinations of switch operation that generate
a hazards to your system.
Bob . . .
-----------------------------------------
( Experience and common sense cannot be )
( replaced with policy and procedures. )
( R. L. Nuckolls III )
-----------------------------------------
Message 4
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--> AeroElectric-List message posted by: "Tom Barter" <kesleyel@IowaTelecom.net>
Bob,
What is your current recommendation for a loadmeter? Searching the archives indicates
that the loadmeter kits are no longer available. Is there another instrument
available that can be modified to indicate system load rather than the
minus -0 -plus ammeter?
Thanks,
Tom Barter
Kesley, IA
Avid Magnum
Message 5
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| Subject: | Help with Diagnosis |
--> AeroElectric-List message posted by: Matt Jurotich <mjurotich@hst.nasa.gov>
My already flying when I bought it RV 6 A has a B&C alternator and a
LR3C-14 voltage regulator. The builder used a 10 amp fuse in the Field
line. Some months ago when I had a low battery, an attempt to jump the
battery got a lot of sparks in the vicinity of the LR3C-14. About 3 flying
hours later the fuse blew and we got home on the battery. Today the fuse
blew again. We landed and replaced the fuse. Everything seemed OK during
taxi and run-up, but the fuse blew again shortly after take-off. Got home
on battery again. Since my home airport is in the DC ADIZ this needs to be
fixed properly. Where do I start to look? A short in the field wire is
the first place, what next? Thanks in advance for the help.
Matthew M. Jurotich
NASA/Goddard Space Flight Center
JWST ISIM Systems Engineer
m/c : 443
e-mail mailto: mjurotich@hst.nasa.gov
phone : 301-286-5919
fax : 301-286-7021
JWST URL: <http://ngst1.gsfc.nasa.gov>
Message 6
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| Subject: | Weird LED fuse behavior |
--> AeroElectric-List message posted by: "John Slade" <sladerj@bellsouth.net>
Here's a strange one for someone....
I have those fuses with an LED that lights up when they blow.
When running my engine for the first time I notice that the LED for the fuel
injection computer (on the essential buss) is glowing, and that the glow
changes in intensity with rpm - i.e. I can light it up more by pushing the
throttle. On shut down I find that the fuse is not blown. I'm not seeing any
charge on the buss from the alternator, and I'm wondering if this may have
something to do with it. Perhaps the alternator solenoid is open, but I
can't see how that would affect voltage or cause some sort of reverse flow
effect.
Any ideas anyone?
John Slade
Cozy IV turbo rotary - making noise
Message 7
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| Subject: | Fw: Transponder arial location |
--> AeroElectric-List message posted by: "Rick Fogerson" <rickf@cableone.net>
----- Original Message -----
From: Rick Fogerson
Subject: Transponder arial location
Hi Bob,
I've got a xpdr arial question for you. I have installed that little 3 inch long
arial with a ball (B&C) belly just aft of the firewall between the exhaust
pipes. The arial would be shielded some in the forward direction by the portion
of the lower cowl where cooling air exits and the exhaust pipes emerge from
the engine compartment. That wasn't a problem when I was going to install the
standard frp cowl but now I thinking of trying to build an aluminum cowl. How
much of a problem do you think this would be?
Thanks,
Rick Fogerson
RV3
Boise, ID
Message 8
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| Subject: | Re: Battery dumps |
--> AeroElectric-List message posted by: "Paul Messinger" <paulm@olypen.com>
Thanks for your comments.
Embedded comments
Subject: AeroElectric-List: Re: Battery dumps
> --> AeroElectric-List message posted by: "Robert L. Nuckolls, III"
<bob.nuckolls@cox.net>
> >I do not see how there is any basic difference (with regard to LOAD
>>DUMP)in
> >internally regulated VS externally regulated Alternators;
>
> The "problem" we're addressing is the fact that some
> alternators with built in regulators will shoot themselves
> between the eyes if the pilot switches them on/off in Figure
> Z-24 with the engine running and with the alternator carrying
> some significant load. This generates something akin to
> the automotive "load dump" except that effects are
> limited to the alternator itself.
>
> Both styles of alternator can be goaded into producing
> a battery-dump surge of output voltage, but for everything
> except Z-24 wiring this has been a rare event and very
> low on the list of concerns.
Rare is not zero however. I still maintain ANY internal or external
regulator controlled alternator will produce a spike if the load is reduced
suddenly removed or reduced. I do not see how the response time of the
regulator is a major factor as the energy is already there and fast response
regulators will only limit the duration, not the peak of the "dump".
I do not agree that procedure alone is sufficent IF there is a solution that
prevents or clips the spike. Also, I am not addressing alternator regulator
damage but potential damage to the acft electrical systems.
After spending tens of thousands on an acft and then skimping a small amount
on adding an external regulator is to me mind boggling (dittos for low
output strobes).
> Many more radios have been smoked
> for lack of ov protection than for any other reason. Experience
> indicates (and DO-160 infers) that once this dragon is adequately
> chained down, probability of letting lots of smoke out of your
> radios is very low.
I agree but many of us have older equipment that may not have the type of OV
protection (per DO -160) to withstand a large "dump" where the voltage
'seems' to get well over 40 V with a simple 5kw 18v device and a 40 amp
dump. I have not fully instrumented it as yet.
Limiting the selection of equipment to certified to DO-160 is not affordable
in many cases.
I only have the materials and time to test my own alternator etc and do not
have a ND internal W/WO external alternator. Thus you may get very
different results. Sorry but every alternator is likely to be somewhat
different.
However, if you have a load bank that can handle 14V at 40 amps and use a
contactor to drop the load you can see what the "dump" is.
I have had no damage with the 5kw 18v device I am using in my setup but
another poster has had failures perhaps only due to the test setup. I am not
placing the TVS at the alternator but several feet away on the power bus
distribution and as such have some series resistance external to the
alternator.
Nor do I have the time (or interest) to try to see if all my equipment will
withstand the resulting OV on the bus. My intent is to clamp the OV at its
source and or prevent the dump from happening in the first place.
I think we agree that if the battery is never taken off line while being
charged, there will be no dump. Other than contactor failure your designs
prevent that IF fully followed. The problem is where a builder fails to see
the reason for your design detail and changes it.
>>s and can be tolerated by
> >the proper TVS. however the TVS may allow a few ms of relatively HV to
> >appear on the main buss that can exceed the equipment ratings.
>
> Only if the equipment is not designed to live in the real
> world of airplanes (or any other vehicle with a DC power
> generation system).
Agree but in the real world there is a lot of low cost equipment available
that some of us can afford that may not meet the real world enviroment and
needs some external help.
> >Mostly agree on Z-24, however, protection from pilot is only part of the
> >concern. I really do not like the use of procedures to prevent equipment
> >damage. Throwing the incorrect switch should never cause damage!
>
> It's not a procedure . . . it's a rational/natural mode of
> operating the airplane. One should not apply rapid full
> travel of flight controls above certain published airspeeds . . .
> okay as far as procedures go but I've never had occasion or
> desire to exercise it. By the same token, I cannot recall a
> single time I felt a need to cycle alternator and/or battery
> switches for anything other than troubleshooting on the ground
> or in the normal course of turning things on during preflight
> and turning things off before I park the airplane.
Many pilots are not as well disciplined and its easy to hit the incorrect
switch in a panic or simply by accident. So I disagree, regardless of the
word used improper or accidental switch actuation should never result in
damage. Guards and or locking levers prevent accidental actuation but does
not prevent bad thinking by the pilot who believes that turning off the
alternator with the engine running is OK.
>
> Even then the alternator always goes off first and does NOT have
> an internal regulator. You can take ANY certified single with
> the infamous split rocker master switch and punch the alternator
> and battery off simultaneously by hitting both sides of the
> switch. This simultaneously disconnects the battery AND the
> alternator field . . . the mechanically linked nature
> of the split-rocker COMBINED with the fact that all spam-cans
> have externally regulated alternators makes this action a non-
> event with respect to battery dump.
Again disagree with ALL. I fly a friends spam can and he lost the external
regulator when electrical smoke appeared in the cockpit and he hit the dual
off rocker. True no avionics were damaged but the alternator regulator was
fried and this was a factory supplied regulator.
In the above case I believe the battery contactor slow opening time of
several MS allowed the alternator to shut\down with no "dump".
> >I am addressing a different case. First, not everyone has your
progressive
> >switches;
All of us do not like toggle switches etc and while its fine to suggest you
use what you have designed in its also worth considering others need to be
able to provide the same safety with "normal" rockers or other styles that
are simple not available in sequential design.
> Can't help it if the reasoning behind the use of
> progressive master switches is misunderstood or ignored.
I suspect there are many who do not fully understand. Perhaps I missed it
but I see no note in appendix Z (just downloaded) describing the requirement
for the sequential switch.
> The split rocker was crafted to address these issues
> 45 years ago . . . and aside from the fact that it
> mounts in a square cornered hole and looks nothing
> like the other switches in the panel, there's nothing
> "wrong" with the split rocker. It's made by Carling
> and has the same guts behind the panel as the 2-10
> toggle switch. The spirit and intent of this switch
> has stood the test of time quite well even if the
> switch itself has been root cause of many unnecessary
> replacements for alternators and regulators in spam-cans.
> The Z-figures have shown either simultaneous or progressive
> disconnection of alternator/battery since day-one. If
> someone chooses to wire their airplane like a Bonanza,
> well . . .
>
> > and you do not seem to address contactor failure. (however
> >unlikely its not zero).
>
> Contactor failure, particularly contactor failure while the
> battery presents a substantial portion of the total alternator
> load is very rare.
>
>
> >Failure of one device should never cause additional failures. I suggest
that
> >a battery contactor failure should not result in a load dump where the
> >alternator is still connected to the main bus. Regardless of the
potential
> >damage of the alternator regulator the main bus gets the impact of the
load
> >dump and prtection needs to be added in my opinion.
>
> The combination of DO-160 qualification and designing electrical
> systems constrained to Mil-STD-704 has a pretty good track record
> for covering all the bases . . . including battery-dump. If one
> chooses to install accessories which are less robust, then there
> are certainly new issues to be considered.
>
>
> >My testing to date has shown to me that the remaining issue is the peak
> >voltage and duration during the TVS protected load dump VS the ability of
> >the equipment to tolerate that transient.
>
> Can you share a repeatable experiments for the tests and the
> data derived therefrom? We've been hashing this topic for
> several weeks now but I've yet to see hard data by which
> one can make rational recommendations for either part
> selection or places where it's a good thing to include
> as part of the system design.
Addressed earlier. I will post what I can when I have accurate info VS a
simple test setup where repeatability and accurate measurements are not
made. I am just looking for rough info at present and what may work as a
clamp.
> Everyone is free to stack as many "firewalls" against the
> extraordinary and unexpected as they wish. I try to avoid
> recommendations for firewalls in favor of designing the risks
> out (which is, in part, what DO-160 is about). I'll be pleased
> to have some real hammer-n-tongs data for color and size of the
> beast. It will be nice if there's a practical, one-part
> solution with sufficient stature to provide a 99% plus
> probability for standing off a battery dump event.
>
>
I think we have such a part today. There is a 500 amp TVS designed
specifically for this subject load dump (mentioned much earlier in ths
thread as I recall). Not stocked, so I went to the 160 amp 5kw part that was
in stock. It seems to work for me and should keep the dump event under
DO-160 testing. However I do have some equipment that appears to be unable
to pass DO-160 and so I am continuing to investigate.
Perhaps my background in space craft is biasing my thinking. There we did
what ever was possible to prevent single point failures regardless of
probability based on real experience that even a 0.0001% probable event can
and did happen.
Perhaps you would like to know that I recommend your "book" etc to other
builders and admonish them to follow the the info 100%. Or ask specific
questions about any deviations (including the use of progressive switches
:-) )
Paul
EAA TC, FA
Message 9
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| Subject: | ?B lead to contactor or to battery? |
--> AeroElectric-List message posted by: "Troy Scott" <tscott1217@bellsouth.net>
Gentlemen,
I note that all the Z drawings show the alternator B lead connected to a
contactor rather than directly to a battery or hot bus. Is this necessarily
always the case? Is this done to facilitate OV protection? Is this more
appropriate to internally regulated alternators that to externally regulated
alternators?
Regards,
Troy Scott
tscott1217@bellsouth.net
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