Today's Message Index:
----------------------
1. 07:35 AM - Re: Re: Alternator Voltage Creeping Up (Robert L. Nuckolls, III)
2. 07:54 AM - Re: Re: Alternator Voltage Creeping Up (Bob Verwey)
3. 07:59 AM - Re: Re: Power, signal, and Coax - How should they be bundled? (Robert L. Nuckolls, III)
4. 08:34 AM - Re: Re: Power, signal, and Coax - How should they be bundled? (Matthew S. Whiting)
Message 1
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| Subject: | Re: Alternator Voltage Creeping Up |
At 10:28 PM 11/20/2023, you wrote:
>
>Check for bad connections that are corroded or loose.
>The problem could also be internal to circuit breakers or switches.
This genere' of regulator senses bus voltage
on the same conductor that supplies field
power. Small increases in resistance of
connections and devices in this pathway
will cause the regulator to believe that
bus voltage is low . . . which is compensated
for by increasing field excitation.
Taken too far, this can lead to the 'galloping
ammeter' phenomenon discussed her on the List
in years past.
Simple experiment to confirm: Acquire a 'test
regulator' from parts store. Get it off the
'net . . . they're cheaper. Fabricate the
test setup depicted here:
http://www.aeroelectric.com/articles/Alternator_Testing.pdf
In this case, you know the alternator is
working so you can leave the meter out of
the test setup.
Make a temporary installation of this fixture
and test fly the airplane. See if the bus
voltage is now stable. If so, refurbish
all connections to components in the field
supply pathway . . . perhaps the components
themselves (field breaker, alternator control
switch).
This is a very common problem with regulators
that DO NOT have separate bus sense leads. It
has plagued thousands of BePipCesMo aircraft
beginning with the first alternator installations
in mid 60's. This was a primary driver for a
design decision to fit B&C regulators with the feature.
Bob . . .
////
(o o)
===========o00o=(_)=o00o========
< Go ahead, make my day . . . >
< show me where I'm wrong. >
================================
In the interest of creative evolution
of the-best-we-know-how-to-do based
on physics and good practice.
Message 2
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| Subject: | Re: Alternator Voltage Creeping Up |
Bob, if you had to buy a regulator for an OBAM aircraft with EFIS and EMS,
and conventional lycoming engine, legacy alternator, what would it be?
On Wed, 22 Nov 2023 at 17:39, Robert L. Nuckolls, III <
nuckolls.bob@aeroelectric.com> wrote:
> At 10:28 PM 11/20/2023, you wrote:
>
>
> Check for bad connections that are corroded or loose.
> The problem could also be internal to circuit breakers or switches.
>
>
> This genere' of regulator senses bus voltage
> on the same conductor that supplies field
> power. Small increases in resistance of
> connections and devices in this pathway
> will cause the regulator to believe that
> bus voltage is low . . . which is compensated
> for by increasing field excitation.
>
> Taken too far, this can lead to the 'galloping
> ammeter' phenomenon discussed her on the List
> in years past.
>
> Simple experiment to confirm: Acquire a 'test
> regulator' from parts store. Get it off the
> 'net . . . they're cheaper. Fabricate the
> test setup depicted here:
>
> http://www.aeroelectric.com/articles/Alternator_Testing.pdf
>
> In this case, you know the alternator is
> working so you can leave the meter out of
> the test setup.
>
> Make a temporary installation of this fixture
> and test fly the airplane. See if the bus
> voltage is now stable. If so, refurbish
> all connections to components in the field
> supply pathway . . . perhaps the components
> themselves (field breaker, alternator control
> switch).
>
> This is a very common problem with regulators
> that DO NOT have separate bus sense leads. It
> has plagued thousands of BePipCesMo aircraft
> beginning with the first alternator installations
> in mid 60's. This was a primary driver for a
> design decision to fit B&C regulators with the feature.
>
>
> Bob . . .
>
> ////
> (o o)
> ===========o00o=(_)=o00o========
> < Go ahead, make my day . . . >
> < show me where I'm wrong. >
> ================================
>
> In the interest of creative evolution
> of the-best-we-know-how-to-do based
> on physics and good practice.
>
--
Best Regards,
Bob Verwey
082 331 2727
Message 3
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| Subject: | Re: Power, signal, and Coax - How should they |
be bundled?
>Your point seemed to be that there is never a problem running power
>and signal lines together so just do it. My point is that this is
>true most of the time, but not all of the time.
Recall that 'power' conductors are potential antagonists
that do their dirty work via magnetic coupling to parallel
conductors. 'signal' conductors are potential victims never
vulnerable if (1) ground loops are designed out of the
system and (2) shields are properly terminated. They are
otherwise vulnerable to electro-static coupling.
For a power conductor to be a nuisance, it must carry
LOTS of 'bumpy current'. The b-lead on an alternator,
a power feeder for hydraulic landing gear pump or really
honky flap system MIGHT be a potential antagonist . . . but
how likely is it that any of these leads might become bundled
with lines carrying micro/millivolt signal levels which
are in turn, poorly configured for noise immunity?
In my whole career, I've encountered only two such
events. One on a car I purchased in OSH where a major
bus feeder got bundled with a speaker lead. I could
barely hear alternator whine in the speaker whether
the radio was on or not. Separating the power lead
by a few inches fixed the problem.
The other was on a Hawker 800 where a cooling blower in the
tail was powered from a source in the cockpit. The
single conductor ran the length of the airplane
sharing a bundle with wires that were signal inputs
to a terribly conceived annunciator system. Inrush
currents to the little blower would cause several
annunciator to illuminate momentarily. Had to tack
some capacitors to the annunciator system inputs
to fix this one.
Energy coupling between parallel conductors is
exceedingly weak so it takes some extra-ordinary
conditions of two or more errors of design
for the problem to manifest.
In our projects, worrying about such things
is not useful.
Bob . . .
////
(o o)
===========o00o=(_)=o00o========
< Go ahead, make my day . . . >
< show me where I'm wrong. >
================================
In the interest of creative evolution
of the-best-we-know-how-to-do based
on physics and good practice.
Message 4
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| Subject: | Re: Power, signal, and Coax - How should they |
be bundled?
I think we are generally in agreement. I never suggested =9Cworrying
=9D about electrical noise, I simply suggested designing it out where it i
s nearly free to do so. Gently twisting wires has a huge effect on noise ge
neration and susceptibility. Professor Van Doren demonstrated that 1 twist p
er inch in a pair of 22 awg wires decreased the mutual inductance by 43 dB c
ompared to untwisted wires. This is 11 dB better than the same untwisted wi
res in a steel conduit (32 dB improvement over baseline)! Since gently twis
ting wires is easy to do, I do it as a matter of course. And SteinAir sells
twisted pair red and black wires ideal for power circuits in aircraft at al
most no price premium compared to the wires bought separately. To me, this i
s just a no-brainer thing to do. If this required significant effort, I wou
ldn=99t bother.
Same with separation of power and signal wires. In my airplane, it is very e
asy to run power down the left side of the fuselage and signal down the righ
t side. No worry required, just a simple precaution that costs virtually no
thing in either dollars or time. So why not? In my case it is actually easi
er as I would need to make larger holes to run everything together down one s
ide. If there was a case where only one hole existed, then I=99d run e
verything through that hole and not lose much sleep. However, if it is equa
lly easy to separate power and signal, I will do that every time.
As I mentioned earlier, my RANS home built is my first aircraft electrical s
ystem design as my experience was in industrial control and data acquisition
systems. So, I claim no specific aircraft design expertise. I have, howev
er, been a pilot since 1978 and have flown a variety of Cessna and Piper air
craft and my experience has been that such aircraft are terrible in regards t
o electrical noise management. I have not flown one yet that didn=99t
have some popping, hissing or static in the headsets. Not a single one. S
o, it isn=99t obvious to me that aircraft designers have paid much att
ention to noise mitigation. My automobiles have been far superior to any GA a
irplane I have flown or owned in this regard. I think the only vehicles whe
re I ever had significant noise issues were made in the 1970s or earlier.
Matt
Sent from my iPad
> On Nov 22, 2023, at 11:01=AFAM, Robert L. Nuckolls, III <nuckolls.bo
b@aeroelectric.com> wrote:
>
> =EF=BB
>>
>> Your point seemed to be that there is never a problem running power
>> and signal lines together so just do it. My point is that this is
>> true most of the time, but not all of the time.
>
> Recall that 'power' conductors are potential antagonists
> that do their dirty work via magnetic coupling to parallel
> conductors. 'signal' conductors are potential victims never
> vulnerable if (1) ground loops are designed out of the
> system and (2) shields are properly terminated. They are
> otherwise vulnerable to electro-static coupling.
>
> For a power conductor to be a nuisance, it must carry
> LOTS of 'bumpy current'. The b-lead on an alternator,
> a power feeder for hydraulic landing gear pump or really
> honky flap system MIGHT be a potential antagonist . . . but
> how likely is it that any of these leads might become bundled
> with lines carrying micro/millivolt signal levels which
> are in turn, poorly configured for noise immunity?
>
> In my whole career, I've encountered only two such
> events. One on a car I purchased in OSH where a major
> bus feeder got bundled with a speaker lead. I could
> barely hear alternator whine in the speaker whether
> the radio was on or not. Separating the power lead
> by a few inches fixed the problem.
>
> The other was on a Hawker 800 where a cooling blower in the
> tail was powered from a source in the cockpit. The
> single conductor ran the length of the airplane
> sharing a bundle with wires that were signal inputs
> to a terribly conceived annunciator system. Inrush
> currents to the little blower would cause several
> annunciator to illuminate momentarily. Had to tack
> some capacitors to the annunciator system inputs
> to fix this one.
>
> Energy coupling between parallel conductors is
> exceedingly weak so it takes some extra-ordinary
> conditions of two or more errors of design
> for the problem to manifest.
>
> In our projects, worrying about such things
> is not useful.
>
> Bob . . .
>
> ////
> (o o)
> ===========o00o=(_)=o00o=======
=
> < Go ahead, make my day . . . >
> < show me where I'm wrong. >
> ========================
========
>
> In the interest of creative evolution
> of the-best-we-know-how-to-do based
> on physics and good practice.
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