Today's Message Index:
----------------------
1. 04:09 AM - Re: Alternator failure thoughts (FLYaDIVE@aol.com)
2. 04:22 AM - Re: Alternator failure thoughts (Gilles Thesee)
3. 04:50 AM - Re: Re: Alternator failure. Info provided (LarryRobertHelming)
4. 05:37 AM - Re: Alternator failure thoughts (Brian Lloyd)
5. 07:29 AM - Re: Alternator failure thoughts (PWilson)
6. 08:13 AM - Re: Alternator failure thoughts (Jim Baker)
7. 09:04 AM - George filter (Fergus Kyle)
8. 09:32 AM - Re: Alternator failure thoughts (John Burnaby)
9. 10:11 AM - Re: Alternator failure thoughts (Hinde, Frank George (Corvallis))
10. 10:19 AM - Battery Contactor - HOT... (Don Honabach)
11. 10:28 AM - Re: Battery Contactor - HOT... (Gilles Thesee)
12. 11:03 AM - Re: Alternator failure thoughts Paul - Barry (PWilson)
13. 11:03 AM - Re: Alternator failure thoughts (Brian Lloyd)
14. 11:10 AM - Re: Battery Contactor - HOT... (Brian Lloyd)
15. 11:36 AM - Re: Battery Contactor - HOT... (FLYaDIVE@aol.com)
16. 11:39 AM - Re: Alternator failure thoughts (Jerry2DT@aol.com)
17. 11:44 AM - Re: Paul's article on modifying ND and MI alternators (Jerry2DT@aol.com)
18. 12:30 PM - Re: Alternator failure thoughts (PWilson)
19. 01:07 PM - Re: Re: Alternator failure thoughts (Brinker)
20. 01:41 PM - Re: Re: Alternator failure thoughts (Hinde, Frank George (Corvallis))
21. 02:17 PM - Re: Re: Alternator failure thoughts ()
22. 03:25 PM - Re: Re: Alternator failure thoughts (Brinker)
23. 04:18 PM - Re: Re: Alternator failure thoughts (Brian Lloyd)
24. 04:30 PM - alternator failure modes (Brian Lloyd)
25. 04:36 PM - Bob's Ground Power Plug button (Robert G. Wright)
26. 04:50 PM - Re: alternator failure modes (Brinker)
27. 05:56 PM - Re: Re: Alternator failure. Info provided (Robert L. Nuckolls, III)
28. 06:15 PM - Strange power source (Terry Watson)
29. 06:48 PM - Annunciator Project (Bret Smith)
30. 07:34 PM - Load Meter Question (PeterHunt1@aol.com)
31. 07:41 PM - Charging System (Jim Butcher)
32. 07:54 PM - Re: Insrument Lighting (Jerry & Ledy Esquenazi)
Message 1
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| Subject: | Re: Alternator failure thoughts |
In a message dated 7/4/2006 9:25:44 PM Eastern Standard Time,
chaztuna@adelphia.net writes:
For the purposes of the alternators we use, the rectifier is
comprised of 6 diodes. These diodes can fail in two modes, open or
short. Failing open (diode blows apart) is the more common
failure mode. In this mode, each diode that fails will reduce the
alternator's output by 1/6th.
Charlie,
Charlie:
Why 6 diodes? Half wave rectification only requires 2 diodes. And Full
wave reverification only requires 4 diodes. So why 6 and how are they hooked
up?
Barry
"Chop'd Liver"
Message 2
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| Subject: | Re: Alternator failure thoughts |
--> AeroElectric-List message posted by: Gilles Thesee <Gilles.Thesee@ac-grenoble.fr>
> Why 6 diodes? Half wave rectification only requires 2 diodes. And
> Full wave reverification only requires 4 diodes. So why 6 and how are
> they hooked up?
>
> Barry
> "Chop'd Liver"
Hi Barry,
Those alternators are 3 phase.
Regards,
Gilles Thesee
Grenoble, France
http://contrails.free.fr
Message 3
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| Subject: | Re: Alternator failure. Info provided |
--> AeroElectric-List message posted by: "LarryRobertHelming" <lhelming@sigecom.net>
Bob, if you want a beta tester when you get the system developed, let me
know. I could be a good candidate. I have new IR 60amp alternator that is
waiting to be installed if the ER alt. from Vans fails which is controlled
by a B&C LR3; but I could make the switch sooner. Larry in Indiana with
flying RV7
> --> AeroElectric-List message posted by: "Robert L. Nuckolls, III"
> <nuckollsr@cox.net>
>
>
> Don't worry about it. There's a system under development
> that's easy to add on to any existing system that provides
> the any-time/any-conditions absolute control over a
> stock automotive alternator. The risks for not having it
> right now are low. If you want OV protection now, you can
> install the original Z-24 configuration knowing that the
> ultimate solution will use the b-lead contactor and alternator
> control switch. The straight transorb approach hypothesized
> on the last figure of page 4 will not work. We've got
> a plan-E . . . or is it "F" . . . anyhow, the solution
> will not be difficult or expensive.
>
> See:
> http://www.aeroelectric.com/articles/Alternator_Failures.pdf
>
>
> Bob . . .
Message 4
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| Subject: | Re: Alternator failure thoughts |
--> AeroElectric-List message posted by: Brian Lloyd <brian-yak@lloyd.com>
On Jul 5, 2006, at 6:57 AM, FLYaDIVE@aol.com wrote:
> In a message dated 7/4/2006 9:25:44 PM Eastern Standard Time,
> chaztuna@adelphia.net writes:
> For the purposes of the alternators we use, the rectifier is
> comprised of 6 diodes. These diodes can fail in two modes, open or
> short. Failing open (diode blows apart) is the more common
> failure mode. In this mode, each diode that fails will reduce the
> alternator's output by 1/6th.
> Charlie,
> Charlie:
>
> Why 6 diodes? Half wave rectification only requires 2 diodes.
For a single winding, half-wave rectification only needs one diode.
> And Full wave reverification only requires 4 diodes. So why 6 and
> how are they hooked up?
It would be possible to write a whole dissertation on this subject.
The alternator is three phase. There are three windings in the stator
of the alternator. Each one by itself produces a full AC wave but
each one has its phase starting 120 degrees after the phase of the
previous winding. Imagine a sine wave starting at zero, rising to a
positive peak at 90 degrees, crossing zero again at 180 degrees,
rising (falling?) to a negative peak at 270 degrees, and then coming
back to zero at 360 degrees to start the whole cycle over again. Now
imagine that the next winding starts its wave at zero just as the
waveform from the first winding is on its downward slope between 90
and 180 degrees. Do this again for the third winding. (This stuff is
hard to describe in words without pictures.)
If you think of how a full-wave bridge rectifier is connected to a
single winding (as in a transformer) You see that each leg of the
transformer has two diodes connected to it -- one going from ground
to the winding and another going from the winding to output. So each
leg of the transformer requires two diodes, one to conduct the
positive half of the cycle to the positive output and the other to
connect the negative half of the cycle to ground.
Since we have a three-phase device we have three windings, not just
one. It turns out that you can save diodes by hooking the three
windings together so you end up with only three leads total. They are
hooked up in either delta configuration or wye ('Y') configuration.
Here, let me try to draw a picture. The letter 'W' will denote a
winding and 'T' will denote a connection terminal:
Delta:
T
/ \
W W
/ \
T---W---T
Wye:
T
|
W
|
t
/ \
W W
/ \
T T
(The center-tap terminal in the wye configuration is often not used
so I made it a small 't'.)
Most alternators are wired in wye configuration. Each of the three
main terminals gets two diodes, one each for the positive and
negative half-cycle of the waveform available at that terminal.
BTW, if your alternator has a 'stator' terminal (the Delco
alternators do) it is usually the center-tap terminal. On boats the
AC at this terminal is used to drive the tachometer. The frequency is
proportional to engine speed. Having your tach drop to zero while the
engine is running is a good indication you have lost your alternator.
(This is how I usually find out I have burned up another stator.)
BTW, if you are wondering about how you can 'short' all the windings
together in the delta configuration without hurting anything you will
find that the voltage at the free ends of any two windings connected
together (vector sum) will be equal and opposite in phase to the
voltage on the other winding so no current will flow.
>
> Barry
> "Chop'd Liver"
Brian Lloyd 361 Catterline Way
brian-yak AT lloyd DOT com Folsom, CA 95630
+1.916.367.2131 (voice) +1.270.912.0788 (fax)
I fly because it releases my mind from the tyranny of petty things . . .
Antoine de Saint-Exupry
Message 5
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| Subject: | Re: Alternator failure thoughts |
--> AeroElectric-List message posted by: PWilson <pwmac@sisna.com>
Its interesting about the number of diodes used
in alternators. The Ford alternator used in
recent vehicles has 8 diodes and a regulator
bolted to the back of the case. I have not been
able to determine if the field wire is externally
accessible. Anyhow, the 95130/160/200amp versions
of the 3G alternator are physically pretty big
for a plane. A schematic and other details can be
found at:
http://fullsizebronco.com/forum/showthread.php?t=55169&highlight=alternator
I would appreciate an explanation of for all the diodes.
The guy who sells the upgraded alternators also
sells various pulleys if anybody has interest.
His link is buried in the above site.
Regards, Paul
=========================
At 06:35 AM 7/5/2006, you wrote:
>--> AeroElectric-List message posted by: Brian Lloyd <brian-yak@lloyd.com>
>
>
>On Jul 5, 2006, at 6:57 AM, FLYaDIVE@aol.com wrote:
>
>>In a message dated 7/4/2006 9:25:44 PM Eastern Standard Time,
>>chaztuna@adelphia.net writes:
>>For the purposes of the alternators we use, the rectifier is
>>comprised of 6 diodes. These diodes can fail in two modes, open or
>>short. Failing open (diode blows apart) is the more common
>>failure mode. In this mode, each diode that fails will reduce the
>>alternator's output by 1/6th.
>>Charlie,
>>Charlie:
>>
>>Why 6 diodes? Half wave rectification only requires 2 diodes.
>
>For a single winding, half-wave rectification only needs one diode.
>
>>And Full wave reverification only requires 4 diodes. So why 6 and
>>how are they hooked up?
>
>It would be possible to write a whole dissertation on this subject.
>
>The alternator is three phase. There are three windings in the stator
>of the alternator. Each one by itself produces a full AC wave but
>each one has its phase starting 120 degrees after the phase of the
>previous winding. Imagine a sine wave starting at zero, rising to a
>positive peak at 90 degrees, crossing zero again at 180 degrees,
>rising (falling?) to a negative peak at 270 degrees, and then coming
>back to zero at 360 degrees to start the whole cycle over again. Now
>imagine that the next winding starts its wave at zero just as the
>waveform from the first winding is on its downward slope between 90
>and 180 degrees. Do this again for the third winding. (This stuff is
>hard to describe in words without pictures.)
>
>If you think of how a full-wave bridge rectifier is connected to a
>single winding (as in a transformer) You see that each leg of the
>transformer has two diodes connected to it -- one going from ground
>to the winding and another going from the winding to output. So each
>leg of the transformer requires two diodes, one to conduct the
>positive half of the cycle to the positive output and the other to
>connect the negative half of the cycle to ground.
>
>Since we have a three-phase device we have three windings, not just
>one. It turns out that you can save diodes by hooking the three
>windings together so you end up with only three leads total. They are
>hooked up in either delta configuration or wye ('Y') configuration.
>Here, let me try to draw a picture. The letter 'W' will denote a
>winding and 'T' will denote a connection terminal:
>
>Delta:
>
> T
> / \
> W W
> / \
> T---W---T
>
>Wye:
>
> T
> |
> W
> |
> t
> / \
> W W
> / \
> T T
>
>(The center-tap terminal in the wye configuration is often not used
>so I made it a small 't'.)
>
>Most alternators are wired in wye configuration. Each of the three
>main terminals gets two diodes, one each for the positive and
>negative half-cycle of the waveform available at that terminal.
>
>BTW, if your alternator has a 'stator' terminal (the Delco
>alternators do) it is usually the center-tap terminal. On boats the
>AC at this terminal is used to drive the tachometer. The frequency is
>proportional to engine speed. Having your tach drop to zero while the
>engine is running is a good indication you have lost your alternator.
>(This is how I usually find out I have burned up another stator.)
>
>BTW, if you are wondering about how you can 'short' all the windings
>together in the delta configuration without hurting anything you will
>find that the voltage at the free ends of any two windings connected
>together (vector sum) will be equal and opposite in phase to the
>voltage on the other winding so no current will flow.
>
>
>>
>>Barry
>>"Chop'd Liver"
>
>Brian Lloyd 361 Catterline Way
>brian-yak AT lloyd DOT com Folsom, CA 95630
>+1.916.367.2131 (voice) +1.270.912.0788 (fax)
>
>I fly because it releases my mind from the tyranny of petty things . . .
> Antoine de Saint-Exupry
>
>
Message 6
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| Subject: | Re: Alternator failure thoughts |
--> AeroElectric-List message posted by: "Jim Baker" <jlbaker@msbit.net>
> Its interesting about the number of diodes used
> in alternators. The Ford alternator used in
> recent vehicles has 8
Recall seeing an article that said Mercedes or BMW (forget
which) uses 12......
Jim Baker
580.788.2779
Elmore City, OK
Message 7
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--> AeroElectric-List message posted by: "Fergus Kyle" <VE3LVO@rac.ca>
Cheers,
I am delighted to see my superiors replying to the bad spelling
and grammar (to say nothing of the manners) of today's millstone. There have
been others - actually they average about one every 18 months. If you ignore
them they run out of opposition and fade away to bother someone else.
However, every tenth should be flogged in the town square at high noon on
Sunday. George is only eighth so not worth the work.
Out of chaos comes opportunity,
out of heated discourse comes understanding and knowledge,.
out of dissonance comes noise,
out of horse manure comes violets,
Out of George comes blow-by
do not archive
Ferg Kyle
Europa A064 914 Classic
Message 8
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| Subject: | Re: Alternator failure thoughts |
I'm not flying yet, but my 60 A ND ER alternator (of undetermined auto
application) has been modified by removing the stamped steel vented rear
cover and replacing it with a fiberglass closed cover with a stub to
accept a blast tube to force air over the diode plate, as an attempt to
compensate for a backward turning alt fan. Aside from buying a B&C or
Plane Power unit, is there a better way? Is this likely to have a
positive effect?
John
Message 9
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| Subject: | Alternator failure thoughts |
Not sure i understand this "backwards turning" deal. Frome what i can
see the internal fan alternators appear to have simply radial fan
blades that simply throw air out thru the sides of the alt. Therby
presumably sucking air in from both front and back.
Adding a cool air supply to the regulator should therefore augment the
existing fan. I am thinking of doing a similar thing by riveting
something similar to the stamped rear cover of my Autozone Toyota Camry
special.
Cetainly couldn't hurt
Frank
________________________________
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of John
Burnaby
Sent: Wednesday, July 05, 2006 8:55 AM
I'm not flying yet, but my 60 A ND ER alternator (of undetermined auto
application) has been modified by removing the stamped steel vented rear
cover and replacing it with a fiberglass closed cover with a stub to
accept a blast tube to force air over the diode plate, as an attempt to
compensate for a backward turning alt fan. Aside from buying a B&C or
Plane Power unit, is there a better way? Is this likely to have a
positive effect?
John
Message 10
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| Subject: | Battery Contactor - HOT... |
I'm in the process of wiring up my panel and noticed that the battery
contactor gets fairly hot (don't have an exact temperature, but so hot
that you wouldn't leave your finger on it for more than a second, but
probably not hot enough to burn you in any 'real' way).
Since I'm only running between 1 to 2A rights now during testing (just a
few instruments connected), I'm assuming the heat is being generated by
the contactor's internal 'switch mechanism'. It also appears to be
hottest at the bottom of the contactor.
Is this normal?
In case you're curious, the unit is a continuous duty contactor and
meant for this type of application.
As always, thanks in advance for your help!
Don
Message 11
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| Subject: | Re: Battery Contactor - HOT... |
--> AeroElectric-List message posted by: Gilles Thesee <Gilles.Thesee@ac-grenoble.fr>
Don Honabach a crit :
>
> Im in the process of wiring up my panel and noticed that the battery
> contactor gets fairly hot (dont have an exact temperature, but so hot
> that you wouldnt leave your finger on it for more than a second, but
> probably not hot enough to burn you in any real way).
>
>
Hi Don,
This seems quite normal to me.
Regards,
Gilles Thesee
Grenoble, France
http://contrails.free.fr
Message 12
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| Subject: | Re: Alternator failure thoughts Paul - Barry |
--> AeroElectric-List message posted by: PWilson <pwmac@sisna.com>
RE: Ford 8 diode alternator
I don't belong to that forum and it pops up without a password
Here is another link that has the same info It works for me and I
don't belong to that forum either.
http://www.foureyedpride.com/phpBB2/viewtopic.php?t=23682
Regards, Paul
====================================
At 10:09 AM 7/5/2006, you wrote:
>Paul:
>
>I could not access the site you gave the link for. Seems it requires a
>password.
>
>http://fullsizebronco.com/forum/showthread.php?t=55169&highlight=alternator
>
>Any other way I can get in, or you could copy the page and send it to me?
>
>Barry
Message 13
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| Subject: | Re: Alternator failure thoughts |
--> AeroElectric-List message posted by: Brian Lloyd <brian-yak@lloyd.com>
On Jul 5, 2006, at 10:23 AM, PWilson wrote:
> I would appreciate an explanation of for all the diodes.
Well, as I said in my earlier post, there are two diodes for each leg
in the stator. You may find some alternators that have diodes in
parallel to carry more current. That would lead to there being 12
diodes in some cases. (Diodes do not parallel well as one diode of a
parallel pair will hog more of the current.)
Nippon Denso adds two more diodes going to the center tap of the wye
which will help the alternator keep going if one of the stator
windings happens to fail open.
If there are more diodes over and above the (basically) six output
diodes then they are there to provide power to the internal
regulator. The most typical system I have seen has three extra diodes
to provide the power to the regulator. Nippon Denso just gets its
regulator power from the B-lead. This means that whenever the battery
is connected to the alternator the alternator is using some amount of
battery power but the full power to the field is not switched on (it
would kill the battery in a couple of hours) until power is applied
to the 'I' lead. This is generally not a problem for an aircraft
application as the battery is disconnected from the alternator when
the battery master contactor is switched off.
In most other alternators there is no way for current to flow from
the battery to the regulator. You either have to provide start-up
power for the regulator through the ignition ('I') or idiot-lamp
('L') terminals, or you have to spin the alternator fast enough that
the residual magnetism in the armature will generate enough to get
the internal regulator to start sending some on to the field.
Does that help?
Brian Lloyd 361 Catterline Way
brian-yak AT lloyd DOT com Folsom, CA 95630
+1.916.367.2131 (voice) +1.270.912.0788 (fax)
I fly because it releases my mind from the tyranny of petty things . . .
Antoine de Saint-Exupry
Message 14
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| Subject: | Re: Battery Contactor - HOT... |
--> AeroElectric-List message posted by: Brian Lloyd <brian-yak@lloyd.com>
On Jul 5, 2006, at 1:14 PM, Don Honabach wrote:
> Im in the process of wiring up my panel and noticed that the
> battery contactor gets fairly hot (dont have an exact temperature,
> but so hot that you wouldnt leave your finger on it for more than
> a second, but probably not hot enough to burn you in any real
> way). ...
> Is this normal?
Yes. There is about 1A flowing through the coil to hold the contactor
closed. Since it is not doing any other work that 1A at 12V is turned
into 12 watts of heat. That is enough to make the contactor get quite
warm. But that is how it is designed to work.
Brian Lloyd 361 Catterline Way
brian-yak AT lloyd DOT com Folsom, CA 95630
+1.916.367.2131 (voice) +1.270.912.0788 (fax)
I fly because it releases my mind from the tyranny of petty things . . .
Antoine de Saint-Exupry
Message 15
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| Subject: | Re: Battery Contactor - HOT... |
--> AeroElectric-List message posted by: FLYaDIVE@aol.com
In a message dated 7/5/06 1:22:49 PM Eastern Daylight Time,
don.honabach@pcperfect.com writes:
> Since I'm only running between 1 to 2A rights now during testing (just a
> few instruments connected), I'm assuming the heat is being generated by
> the contactor's internal 'switch mechanism'. It also appears to be
> hottest at the bottom of the contactor.
========================================
Don:
I can understand WARM but not HOT! I honestly have never checked the
temperature of the Master or Starter relays but so hot that you can't touch it
and
keep your fingers on it does NOT seem correct.
My first thought is ... Did you Mix Up the relays? The Master Relay is rated
as CONTINUOUS DUTY while the Starter Relay is rated only INTERMITTENT DUTY.
If you mixed them up then SURE! The one used as Master would get HOT ...
Probably Very HOT!
Barry
"Chop'd Liver"
Message 16
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| Subject: | Re: Alternator failure thoughts |
Charlie, IIRC you are an automotive technician so I am curious... In your
years in that industry, how many alternators did you see fail mechanically
enough to toss parts and pieces around? Before I retired 8 years ago, I owned a
shop with 4 busy mechanics, many alternator failures we saw, but I don't
recall one that destroyed itself that way. We saw a few that seized and destroyed
the belt, but that's about it.
Jerry Cochran
>snipped
>I have seen a number of alternator failures on cars, boats, and
>airplanes. Some were pretty simple, no-brainer failures and some were
>"HOLY S--T" failures. I thought I would toss in here the ways I can
>see alternators failing (and have failed) and then address the failures.
>
>Here are the failure modes I have see so far (feel free to add to
>this list):
>
>1. Straight electrical failures:
>
> a. regulator failed -- no output
> b. brushes failed -- no output
> c. output diode failure -- whine and reduced output
> d. diode trio failure -- no output
> e. regulator failed -- runaway output (destroys battery and
> anything
>else attached to the bus)
snipped
Brian,
I'd like to expand on item C of the list above
Output diodes comprise the rectifier. (converts AC current to
DC) For the purposes of the alternators we use, the rectifier is
comprised of 6 diodes. These diodes can fail in two modes, open or
short. Failing open (diode blows apart) is the more common failure
mode. In this mode, each diode that fails will reduce the
alternator's output by 1/6th.
Diodes that fail shorted are more insidious. Often, the pilot will
not notice a decrease in performance. However, he/she will generally
notice an increase in noise (generally on the radios) This is because
1/6th of the alternator's output is now bleeding through as AC
current. The ship's electrical system is designed for DC current. The
one item which really can not tolerate AC current is the battery. Any
time an alternator fails, it is best to do a postmortem, to determine
the cause.
Shorted rectifier diodes which are not repaired promptly, will soon
destroy the battery's storage capacity. This damage to the battery
may not be noticed, without conducting a battery output test. This is
important if you subscribe to Bob N's ideas regarding battery only
emergency operations.
Charlie Kuss
Message 17
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| Subject: | Re: Paul's article on modifying ND and MI alternators |
Paul,
I trust you'll give us a headsup when that update is available? Thanks for
your contribution. Do not archive.
Jerry Cochran
alternators
--> AeroElectric-List message posted by: "Paul Messinger" <paulm@olypen.com>
Thanks; I will be updating the article as a PDF with current info and part
numbers etc as needed. Need a couple of weeks to complete but it will not be
limited to the mag article for photo size and resolution etc.
Paul
Message 18
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| Subject: | Re: Alternator failure thoughts |
--> AeroElectric-List message posted by: PWilson <pwmac@sisna.com>
Thanks Brian it helps
===============
At 11:57 AM 7/5/2006, you wrote:
>--> AeroElectric-List message posted by: Brian Lloyd <brian-yak@lloyd.com>
>
>On Jul 5, 2006, at 10:23 AM, PWilson wrote:
>
>>I would appreciate an explanation of for all the diodes.
>
>Well, as I said in my earlier post, there are two diodes for each leg
>in the stator. You may find some alternators that have diodes in
>parallel to carry more current. That would lead to there being 12
>diodes in some cases. (Diodes do not parallel well as one diode of a
>parallel pair will hog more of the current.)
>
>Nippon Denso adds two more diodes going to the center tap of the wye
>which will help the alternator keep going if one of the stator
>windings happens to fail open.
>
>If there are more diodes over and above the (basically) six output
>diodes then they are there to provide power to the internal
>regulator. The most typical system I have seen has three extra diodes
>to provide the power to the regulator. Nippon Denso just gets its
>regulator power from the B-lead. This means that whenever the battery
>is connected to the alternator the alternator is using some amount of
>battery power but the full power to the field is not switched on (it
>would kill the battery in a couple of hours) until power is applied
>to the 'I' lead. This is generally not a problem for an aircraft
>application as the battery is disconnected from the alternator when
>the battery master contactor is switched off.
>
>In most other alternators there is no way for current to flow from
>the battery to the regulator. You either have to provide start-up
>power for the regulator through the ignition ('I') or idiot-lamp
>('L') terminals, or you have to spin the alternator fast enough that
>the residual magnetism in the armature will generate enough to get
>the internal regulator to start sending some on to the field.
>
>Does that help?
>
>Brian Lloyd 361 Catterline Way
>brian-yak AT lloyd DOT com Folsom, CA 95630
>+1.916.367.2131 (voice) +1.270.912.0788 (fax)
>
>I fly because it releases my mind from the tyranny of petty things . . .
> Antoine de Saint-Exupry
>
>
Message 19
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| Subject: | Re: Alternator failure thoughts |
I have run a auto salvage business for 20 years and I cannot
recall ever seeing or hearing of an exploded alternator. I have seen
many of them seized up as you mention. It is hard to say how many I've
sold (several thousand I would guess) And I have never heard of any
damage to an auto engine resulting from an alternator seize. I would
guess most auto engines will cruise somewhere between 2000 and 3000 rpms
which would put it close to what an airplane engine is run. But on a
long drive I would guess the alternator would see 4000 and above rpm's
in an automobile many times while downshifting to pass, going uphill,
accelerating from stop etc, which in an airplane the max will normally
be around 2700 rpm. Accually the alt itself would see a much higher rpm
possibly twice or more that of the engine rpm's since the crank pulley
is generally at least twice the circumference of the alt pulley on an
auto engine and probably around 3 times difference on the airplane crank
vs. alt pulley. Which would make the alt rpm's much higher than an auto
if the same sized alt pulley. Taking into consideration the higher rpm's
of the auto engine the alt maximum seen rpm's difference between the
aircraft and auto alt's would be somewhere close I would think,
especially if the airplane alt pulley was larger. I am not saying that
an alt seizing cannot explode or damage an engine but I would think it
very rare. My observations are deffinately not scientific but I should
think a good indicator of the rarity.
Randy
----- Original Message -----
From: Jerry2DT@aol.com
To: aeroelectric-list@matronics.com
Sent: Wednesday, July 05, 2006 1:37 PM
Subject: AeroElectric-List: Re: Alternator failure thoughts
Charlie, IIRC you are an automotive technician so I am curious... In
your years in that industry, how many alternators did you see fail
mechanically enough to toss parts and pieces around? Before I retired 8
years ago, I owned a shop with 4 busy mechanics, many alternator
failures we saw, but I don't recall one that destroyed itself that way.
We saw a few that seized and destroyed the belt, but that's about it.
Jerry Cochran
From: Charlie Kuss <chaztuna@adelphia.net>
Subject: Re: AeroElectric-List: Alternator failure thoughts
>snipped
>I have seen a number of alternator failures on cars, boats, and
>airplanes. Some were pretty simple, no-brainer failures and some
were
>"HOLY S--T" failures. I thought I would toss in here the ways I can
>see alternators failing (and have failed) and then address the
failures.
>
>Here are the failure modes I have see so far (feel free to add to
>this list):
>
>1. Straight electrical failures:
>
> a. regulator failed -- no output
> b. brushes failed -- no output
> c. output diode failure -- whine and reduced output
> d. diode trio failure -- no output
> e. regulator failed -- runaway output (destroys battery
and
> anything
>else attached to the bus)
snipped
Brian,
I'd like to expand on item C of the list above
Output diodes comprise the rectifier. (converts AC current to
DC) For the purposes of the alternators we use, the rectifier is
comprised of 6 diodes. These diodes can fail in two modes, open or
short. Failing open (diode blows apart) is the more common failure
mode. In this mode, each diode that fails will reduce the
alternator's output by 1/6th.
Diodes that fail shorted are more insidious. Often, the pilot will
not notice a decrease in performance. However, he/she will generally
notice an increase in noise (generally on the radios) This is
because
1/6th of the alternator's output is now bleeding through as AC
current. The ship's electrical system is designed for DC current.
The
one item which really can not tolerate AC current is the battery.
Any
time an alternator fails, it is best to do a postmortem, to
determine
the cause.
Shorted rectifier diodes which are not repaired promptly, will
soon
destroy the battery's storage capacity. This damage to the battery
may not be noticed, without conducting a battery output test. This
is
important if you subscribe to Bob N's ideas regarding battery only
emergency operations.
Charlie Kuss
Message 20
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| Subject: | Re: Alternator failure thoughts |
The standard large pully on lyc is around 9.5 inches so the alt speed
does get up there even at a cruise of around 2400 RPM.
Mind you if the alt seized I'm sure it would simply vapourise the belt.
Can't imaging the belt will absorb more than 30HP without breaking.
Hard to see it stopping an engine....At leats I hope not...:)
Frank
________________________________
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
Brinker
Sent: Wednesday, July 05, 2006 1:06 PM
I have run a auto salvage business for 20 years and I cannot
recall ever seeing or hearing of an exploded alternator. I have seen
many of them seized up as you mention. It is hard to say how many I've
sold (several thousand I would guess) And I have never heard of any
damage to an auto engine resulting from an alternator seize. I would
guess most auto engines will cruise somewhere between 2000 and 3000 rpms
which would put it close to what an airplane engine is run. But on a
long drive I would guess the alternator would see 4000 and above rpm's
in an automobile many times while downshifting to pass, going uphill,
accelerating from stop etc, which in an airplane the max will normally
be around 2700 rpm. Accually the alt itself would see a much higher rpm
possibly twice or more that of the engine rpm's since the crank pulley
is generally at least twice the circumference of the alt pulley on an
auto engine and probably around 3 times difference on the airplane crank
vs. alt pulley. Which would make the alt rpm's much higher than an auto
if the same sized alt pulley. Taking into consideration the higher rpm's
of the auto engine the alt maximum seen rpm's difference between the
aircraft and auto alt's would be somewhere close I would think,
especially if the airplane alt pulley was larger. I am not saying that
an alt seizing cannot explode or damage an engine but I would think it
very rare. My observations are deffinately not scientific but I should
think a good indicator of the rarity.
Randy
----- Original Message -----
From: Jerry2DT@aol.com
To: aeroelectric-list@matronics.com
Sent: Wednesday, July 05, 2006 1:37 PM
Subject: AeroElectric-List: Re: Alternator failure thoughts
Charlie, IIRC you are an automotive technician so I am
curious... In your years in that industry, how many alternators did you
see fail mechanically enough to toss parts and pieces around? Before I
retired 8 years ago, I owned a shop with 4 busy mechanics, many
alternator failures we saw, but I don't recall one that destroyed itself
that way. We saw a few that seized and destroyed the belt, but that's
about it.
Jerry Cochran
From: Charlie Kuss <chaztuna@adelphia.net>
Subject: Re: AeroElectric-List: Alternator failure
thoughts
>snipped
>I have seen a number of alternator failures on cars,
boats, and
>airplanes. Some were pretty simple, no-brainer failures
and some were
>"HOLY S--T" failures. I thought I would toss in here
the ways I can
>see alternators failing (and have failed) and then
address the failures.
>
>Here are the failure modes I have see so far (feel free
to add to
>this list):
>
>1. Straight electrical failures:
>
> a. regulator failed -- no output
> b. brushes failed -- no output
> c. output diode failure -- whine and reduced
output
> d. diode trio failure -- no output
> e. regulator failed -- runaway output
(destroys battery and
> anything
>else attached to the bus)
snipped
Brian,
I'd like to expand on item C of the list above
Output diodes comprise the rectifier. (converts AC
current to
DC) For the purposes of the alternators we use, the
rectifier is
comprised of 6 diodes. These diodes can fail in two
modes, open or
short. Failing open (diode blows apart) is the more
common failure
mode. In this mode, each diode that fails will reduce
the
alternator's output by 1/6th.
Diodes that fail shorted are more insidious. Often,
the pilot will
not notice a decrease in performance. However, he/she
will generally
notice an increase in noise (generally on the radios)
This is because
1/6th of the alternator's output is now bleeding through
as AC
current. The ship's electrical system is designed for DC
current. The
one item which really can not tolerate AC current is the
battery. Any
time an alternator fails, it is best to do a postmortem,
to determine
the cause.
Shorted rectifier diodes which are not repaired
promptly, will soon
destroy the battery's storage capacity. This damage to
the battery
may not be noticed, without conducting a battery output
test. This is
important if you subscribe to Bob N's ideas regarding
battery only
emergency operations.
Charlie Kuss
Message 21
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| Subject: | Re: Alternator failure thoughts |
--> AeroElectric-List message posted by: <chaztuna@adelphia.net>
---- Jerry2DT@aol.com wrote:
>
> Charlie, IIRC you are an automotive technician so I am curious... In your
> years in that industry, how many alternators did you see fail mechanically
> enough to toss parts and pieces around? Before I retired 8 years ago, I owned
a
> shop with 4 busy mechanics, many alternator failures we saw, but I don't
> recall one that destroyed itself that way. We saw a few that seized and destroyed
> the belt, but that's about it.
>
> Jerry Cochran
snipped
Jerry,
I, like you, own an auto repair shop. I have never in 30+ years seen an automobile
alternator "explode". It just doesn't happen. What did happen, back in the
days when cars mounted alternators like is done on light aircraft, was that
the adjuster bracket cracked and broke. The alternator then starts bouncing
around. If the driver didn't shut the engine down fairly soon, it would attempt
to depart the engine. On most light aircraft, the normal operating noises would
preclude any chance of you hearing this situation in time to do anything about
it.
You have two brackets, the pivot bracket and the adjuster bracket. The adjuster
bracket is the long arm with the slotted hole in it. These brackets broke with
some regularity back before the use of large cast mounting and tensioning pulleys.
They would break for one of two reasons.
#1 The brackets were under designed for the load. I think that the bracket supplied
by Vans Aircraft is marginal here. (I'm building an RV-8A, so that's my
reference point with experimental aircarft)
#2 Due to carelessness or poor workmanship during an alternator replacement, a
mechanic omitted some of the retaining hardware for the alternator or it's brackets.
Most common was loosing the large "fender" (think AN970) washer between the adjuster
bolt and the slotted hole in the adjuster bracket. This would concentrate
the vibratory stresses around the hex head of the bolt at the adjuster bracket.
The adjuster bracket is weak due to the adjustment slot machined (or broached)
into it. The purpose of the fender washer was to spread the stress over
an area large enough to absorb it, and to reinforce this less than steller mount
design.
I also have a background in aerospace machine assembly. I was taught that any
metal surface less than 1/4" thick should have a flat washer installed between
the bolts (or nut) and the surface it bore down on (in this case the bracket)
Another rule of thumb is that all brackets should be triangulated. By this I mean
that they should have 3 mounting points. Two points should attach to the engine
and one to the alternator.
Many aviation (and decades old cars) did not meet either of these engineering
rules of thumb. Most RV alternator adjusting brackets have this failing. The adjustment
bracket mounts to the engine with only one fastener and to the alternator
with one fastener. Compound the problem with the following agrivating conditions.
#1 The 4 cylinder Lycoming's reputation to mimic a wet dog during start up and
shut down.
#2 An adjustment slot that is much longer than necessary to do the job.
So you have 3 conditions which are trying to destroy your adjustment bracket. I
suggest to the listers that they ensure that their alternator mounting system
is stout enough to do the job. Also take care when installing and removing the
mounting hardware to it.
Charlie Kuss
Message 22
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| Subject: | Re: Alternator failure thoughts |
Thanks for that info. I have a loose IO-540 flywheel that
measures 9 3/4" I measured it to the outside, Lyc. may get their
measurement from down in the groove. That spurred me to check some
automobile measurements (I have aprox. 150 or so engines on my engine
rack from anything from a chevy v-8 to a 4cyl foreign) It was
interesting to see the varying sizes on the crankshaft pulley's, they
ranged from aprox. 4 1/2" to 8". Of course many of them had double and
triple pulley system, so not sure which one would have been the alt.
pulley. Although the largest 8" was a single crank pulley system off of
a 99 Plymouth Breeze ( I am 99% sure it was a single pulley system, I
found no indications of any other pulleys that may have been bolted to
it).
I also went thru my alternator racks and got various
different pulley measurements. They ranged from aprox. 2 1/4" to 2 7/8"
although I am almost certain I have seen some over 3" in diameter in the
past but just not on the rack at this time.
Keep in mind these measurements we're all outside pulley
measurements. I did not even try to figure the diameter where the belt
accually rides. I would guess the shoulder measurements we're anywhere
from 1/8" to 1/4" on the serpintine types and probably around 1/2" deep
for the v-belt type.
So from my perspective, there are some auto's that approach the
Lyc. flywheel size so the alt. rpm's difference would not be extremely
far apart and some of the auto alt's would probably surpass the airplane
alt. rpm speed ( although most do not ) while in an acceleration. But
even if only say 10% of the auto alt's would exceed the airplanes rpm's
even only 10% of the time that would be I believe a significant enough
number to say that if it we're a real world problem with them exploding
we would have seen at least one.
Nope not exactly scientific data but I hope this may give some
perspective. Of course I thru in some Randy rambling logic for free.
Sorry for the rant.
Rambling Randy
----- Original Message -----
From: Hinde, Frank George (Corvallis)
To: aeroelectric-list@matronics.com
Sent: Wednesday, July 05, 2006 3:36 PM
Subject: RE: AeroElectric-List: Re: Alternator failure thoughts
The standard large pully on lyc is around 9.5 inches so the alt speed
does get up there even at a cruise of around 2400 RPM.
Mind you if the alt seized I'm sure it would simply vapourise the
belt. Can't imaging the belt will absorb more than 30HP without
breaking. Hard to see it stopping an engine....At leats I hope not...:)
Frank
-------------------------------------------------------------------------
-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
Brinker
Sent: Wednesday, July 05, 2006 1:06 PM
To: aeroelectric-list@matronics.com
Subject: Re: AeroElectric-List: Re: Alternator failure thoughts
I have run a auto salvage business for 20 years and I cannot
recall ever seeing or hearing of an exploded alternator. I have seen
many of them seized up as you mention. It is hard to say how many I've
sold (several thousand I would guess) And I have never heard of any
damage to an auto engine resulting from an alternator seize. I would
guess most auto engines will cruise somewhere between 2000 and 3000 rpms
which would put it close to what an airplane engine is run. But on a
long drive I would guess the alternator would see 4000 and above rpm's
in an automobile many times while downshifting to pass, going uphill,
accelerating from stop etc, which in an airplane the max will normally
be around 2700 rpm. Accually the alt itself would see a much higher rpm
possibly twice or more that of the engine rpm's since the crank pulley
is generally at least twice the circumference of the alt pulley on an
auto engine and probably around 3 times difference on the airplane crank
vs. alt pulley. Which would make the alt rpm's much higher than an auto
if the same sized alt pulley. Taking into consideration the higher rpm's
of the auto engine the alt maximum seen rpm's difference between the
aircraft and auto alt's would be somewhere close I would think,
especially if the airplane alt pulley was larger. I am not saying that
an alt seizing cannot explode or damage an engine but I would think it
very rare. My observations are deffinately not scientific but I should
think a good indicator of the rarity.
Randy
Message 23
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| Subject: | Re: Alternator failure thoughts |
--> AeroElectric-List message posted by: Brian Lloyd <brian-yak@lloyd.com>
On Jul 5, 2006, at 4:36 PM, Hinde, Frank George (Corvallis) wrote:
> The standard large pully on lyc is around 9.5 inches so the alt
> speed does get up there even at a cruise of around 2400 RPM.
> Mind you if the alt seized I'm sure it would simply vapourise the
> belt. Can't imaging the belt will absorb more than 30HP without
> breaking. Hard to see it stopping an engine....At leats I hope
> not...:)
I think it more likely that the mounting ears could break and the
alternator could find itself bouncing around in the cowling. I don't
think it will turn into a grenade but who knows.
Brian Lloyd 361 Catterline Way
brianl at lloyd dot com Folsom, CA 95630
+1.916.367.2131 (voice) +1.270.912.0788 (fax)
"Five percent of the people think.
Ten percent of the people think they think.
Eighty-five percent of the people would rather die than think."
---Thomas A. Edison
Brian Lloyd 361 Catterline Way
brian-yak AT lloyd DOT com Folsom, CA 95630
+1.916.367.2131 (voice) +1.270.912.0788 (fax)
I fly because it releases my mind from the tyranny of petty things . . .
Antoine de Saint-Exupry
Message 24
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| Subject: | alternator failure modes |
--> AeroElectric-List message posted by: Brian Lloyd <brian-yak@lloyd.com>
I have had several people write to me to tell me that they have never
seen an alternator turn into a grenade. Neither have I. I was just
listing that is a *possible* scenario, as in, "I suppose this might
happen." I think it unlikely but I do think that things like broken
brackets, having the alternator seize, and who knows what happens if
both happen at once.
The key point is that there are mechanical failure modes, not just
electrical failure modes. When the alternator stops producing power
it is not just an electrical problem. If one were to fly for a longer
period of time something bad could happen that would make the
situation much worse.
I still hold that it is a good idea to land and check things out even
if you have a backup alternator or lots of battery capacity.
Brian Lloyd 361 Catterline Way
brian-yak AT lloyd DOT com Folsom, CA 95630
+1.916.367.2131 (voice) +1.270.912.0788 (fax)
I fly because it releases my mind from the tyranny of petty things . . .
Antoine de Saint-Exupry
Message 25
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| Subject: | Bob's Ground Power Plug button |
I've been slowly working on Bob Nuckolls' design for the ground power plug
made out of the Cole-Hersey Piper-style plug/socket. I couldn't get the
insulating button out with pliers or other methods so I figured I'd try to
be careful as I heated up the rear screw for solder. Of course, it got too
hot and melted. I emailed Cole-Hersey (CH) on the website and got a message
to call local dealers. Dealers, come to find out, don't carry little parts,
just the end item.
I finally talked to someone at CH who had to go down to the assembly
line/warehouse to find the little buttons, then sent me four for free when I
only requested one that I would pay for, and who was also kind enough to
write the part number on the little baggie when she sent them to me.
Awesome job at customer service. If anyone else has had this problem,
before you go buy a new plug or find a decades-old salvage part, call CH up
and ask for part number 11055-25.
Rob Wright
RV-10 #392
Message 26
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| Subject: | Re: alternator failure modes |
--> AeroElectric-List message posted by: "Brinker" <brinker@cox-internet.com>
Yep it's not like we can coast to the side of the road when we have a
major problem. Better safe than sorry. And hey we might even make a friend
at our non scheduled destination. If there's one thing I've noticed in my
relatively short flying experiences is that airport folks are generally
friendly and willing to help.
Randy
----- Original Message -----
Sent: Wednesday, July 05, 2006 6:07 PM
> --> AeroElectric-List message posted by: Brian Lloyd <brian-yak@lloyd.com>
>
> I have had several people write to me to tell me that they have never
> seen an alternator turn into a grenade. Neither have I. I was just
> listing that is a *possible* scenario, as in, "I suppose this might
> happen." I think it unlikely but I do think that things like broken
> brackets, having the alternator seize, and who knows what happens if both
> happen at once.
>
> The key point is that there are mechanical failure modes, not just
> electrical failure modes. When the alternator stops producing power it is
> not just an electrical problem. If one were to fly for a longer period of
> time something bad could happen that would make the situation much worse.
>
> I still hold that it is a good idea to land and check things out even if
> you have a backup alternator or lots of battery capacity.
>
> Brian Lloyd 361 Catterline Way
> brian-yak AT lloyd DOT com Folsom, CA 95630
> +1.916.367.2131 (voice) +1.270.912.0788 (fax)
>
> I fly because it releases my mind from the tyranny of petty things . . .
> Antoine de Saint-Exupry
>
>
> http://www.matronics.com/Navigator?AeroElectric-List
> http://wiki.matronics.com
>
>
>
Message 27
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| Subject: | Re: Alternator failure. Info provided |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckollsr@cox.net>
At 06:47 AM 7/5/2006 -0500, you wrote:
>--> AeroElectric-List message posted by: "LarryRobertHelming"
><lhelming@sigecom.net>
>
>Bob, if you want a beta tester when you get the system developed, let me
>know. I could be a good candidate. I have new IR 60amp alternator that
>is waiting to be installed if the ER alt. from Vans fails which is
>controlled by a B&C LR3; but I could make the switch sooner. Larry in
>Indiana with flying RV7
I'll keep it in mind. There will be some beta-systems shipped
to builders who are willing and able to provide best-practical
turn-around for proofing installation instructions and product
performance.
Thanks for the offer!
Bob . . .
Message 28
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| Subject: | Strange power source |
I got this today from a relative who lives in Florida:
.our son-in-law, had an underground electrical service line burn up about
two months ago. The electric company came with a two wheel hand truck
mounted metal box (heavy, had a hoist on it to get it back in the truck) to
replace his electric service. They cut the service line into his meter,
removed it, plugged in, and then plugged back in the meter. It ran his
house for over a month, including air conditioner, water heater, stove, etc.
I crawled all over the device, and there was not a line coming to it. It
worked just like a battery, and was silent. I could not find a manufactures
nameplate, a property number, any thing but a number stamped into the box
with the word "Deland" (name of the town that the service company is located
in).
What a hell of a backup generator, and with the wheels on it, we could just
lift the hood, roll it into the front of our vehicle, and replace the "gas
burner". I'm not making much progress in locating the manufacturer of this
device (has to be a fuel cell). Progress Energy, headquartered in the
Carolinas, is the electric company. If you see anything, let me know, this
thing was awesome.
I thought one of you might know more about what he is talking about. Sounds
interesting!
Terry
RV-8A
Seattle
Message 29
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| Subject: | Annunciator Project |
Bob,
Speaking of test projects, have you heard anything from your "design crew"
about the annunciator project? Prospective buyers want to know.
Bret Smith
RV-9A (91314)
Mineral Bluff, GA
www.FlightInnovations.com
Message 30
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| Subject: | Load Meter Question |
Bob:
When I first installed the load meter you sold me it read 25%. Now, with
the same instruments/electrical equipment on it reads 16%. The decrease from
25% to 16% has taken place gradually over the past 20 hours of flight time and
it just seems to me that this decrease is substantial. No lights,
instruments or other electrical equipment have failed. Any thoughts on what may
be
causing this decrease in load meter reading?
Pete in Clearwater
RV-6, Reserve Grand Champion - Kit, Sun 'n Fun 2006
All electric panel
Heading for Oshkosh
Message 31
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I'm having difficulty trouble shooting a charging system problem. The
install is a Rotax 914 in an Europa XS. Besides the Rotax alternator, I
have a B&C L60 alternator driven off the crankshaft and a B&C LR3C
regulator. The electrical system is basically AeroElectric Z-13. I have
recently completed the 50 hour inspection of the airframe and engine.
There were no problems found with the charging system and the battery
(Panasonic LC-X1220P 20 aH) is only 18 mos old with 50 hours of use. It
passed a capacity test with the same result as when new.
The aircraft is equipped with 3 ammeters - one on the battery positive
and one on each alternator output. What I observed during flight and
subsequent testing today is that the battery ammeter shows -3 amps (a 3
amp discharge) all the time, regardless of load - ie turning on pitot
heat doesn't change the value - it's still a 3 amp discharge. Data from
flights prior to the maintenance showed 0 amps at this spot as expected.
The problem is present with either alternator on line and both of them
operate correctly, proven by loading heavily (pitot heat) and noting the
amp output.
Any suggestions on where to look? Might there be a problem with this
battery where it can't accept a charge properly? The bus voltage runs
14.1 - 14.2 volts which is what B&C recommends.
Thanks
Jim Butcher
Europa XS N241BW
Message 32
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| Subject: | RE: Insrument Lighting |
Hey Guys,
Thanks to Eric, Ken , and Charlie for your suggestions. However, I
don't have any idea on how to build a PWM or variable duty cycle
circuit. Do you guys have any schematics or more info? Thanks Charlie
for including the link.
I don't plan on disconnecting the instrument or covering it up. I
have the g-meter lit for aesthetics and symmetry. I paid extra to have
it lit, so I plan on using it.
I called the manufacturer of the g-meter. The reason the instrument
is so bright is that it actually has three bulbs drawing a total of
0.56. The company verified my amp draw correct for a 12 v unit. So at
least I know I have the right bulbs. I still need to dim it down a bit
to make the brightness similar to the rest of the instruments. Bob K.,
do you have any ideas?
Thank you,
Jerry
--> AeroElectric-List message posted by: Ken <klehman@albedo.net>
Hi Jerry
I'd say you did it all correctly but you are just surprised at how much
the 2.5 watts heats up a resistor. A 5 watt bulb is about what
incandescent children's night lights are and does seem ridiculous for an
instrument so I agree that is is the wrong bulb. I would leave it as is
with your resistor. Second choice would be change the bulb to one that
is really 12 volts. Third choice is a variable duty cycle circuit that
pulses short 12 volt pulses to the lamp so that it averages the same
power as running it on 5 volts. That avoids heating up a resistor and
dumping the 2.5 watts but I doubt it is worth the trouble. Fourth choice
is kind of silly but if you had another similar instrument you could
wire them is series...
Ken
Jerry & Ledy Esquenazi wrote:
> Hey Guys,
> I have a simple problem that most likely has a simple solution.
> The solution, however, eludes me. I have an internally lit g-meter on
> my instrument panel (Don't ask me why :-)). The g-meter's lighting is
> internal to the instrument, i.e. it's not a lighting tray that is
> screwed to the top. The instrument would have to be opened up to get
> to the lamp.
>
> I purchased the g-meter from Chief a while back ago, and when I
> received it, I realized it was a 5v unit. Chief didn't have any other
> lighting option listed or available. I thought about dropping the
> voltage with a resistor. Before doing this I called the manufacturer
> Wultrad (aka Falcon Gauge). They said they had a 12v unit in stock
> that they could swap for mine. I thought... "great problem solved."
> They shipped me one back with a 12v label over the original label. In
> testing my instrument panel lighting, I discovered that the g-meter is
> considerably brighter than the other instruments to the point it would
> be annoying at night. The interesting thing is the light is nice and
> white and very uniform though out the face of the instrument. Anyway,
> I thought... "gee I'm back to putting in a resistor to dim the light!"
>
> "OK, no problem. I'll figure out what size resistor I need and
> move on," I thought. The problem is the resistance of any
> incandescent lamp changes whether it hot or cold. The lamp is drawing
> 0.56 A at 12.0 v. Seem's like a lot to me. From that I deduced the
> lamp's resistance at 21.3 ohm. The problem is that when I figure out
> what size resistor I need to get say a 7 or 8 v voltage drop across
> the lamp and add that resistor to the circuit, the current changes and
> so does the resistance of the lamp. So how does one figure this stuff
> out? I decided to purchase a potentiometer and install it in my
> circuit, adjust it 'till I got the brightness I wanted and then
> measure the resistance of the pot. In doing this I began to smell
> smoke, the little pot was beginning to glow red as I dimmed down the
> light in the instrument. I went back and purchased a heavier pot.
> This did the trick. I decided a 20 ohm resistor in series would be
> perfect. I purchased a 22 ohm, 2 W resistor, temporarily installed
> it, and the light was perfect. The problem was I was still smelling
> that familiar acrid smell. I had a 7.4 v drop across the resistor and
> a .34 A current giving me 2.5 W to dissipate. I later tried two 10
> ohm, 2 W resistors in series. Still, they got too hot. I purchased a
> ceramic 22 ohm, 5 W resistor and it still got too hot to touch. The
> small battery I was using for testing was putting out 12.2 v under the
> load. I had a 7.4 v drop across the resistor, So I deduced I must be
> getting a 4.8 v drop across the lamp. The light was just right. I
> wonder if I still have a 5v lamp inside the instrument! I measured
> 0.34 A in the circuit. The 5 W resistor ought to be handling the 2.5
> W I need to dissipate just fine. Something is wrong. Do any of you
> smart guys know what I'm doing wrong?
>
> Jerry
> "Smelling smoke in Georgia
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