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jonlaury
Joined: 06 Nov 2006
Posts: 336
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 Posted: Tue May 11, 2010 9:23 am Post subject: Alternator cooling |
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After scouring the archives and only one post on topic, I come to you all with an Alternator cooling question.
My alternators are driven off a spur gear and hence turn opposite to their intended direction. I've built fiberglass "caps" with blast tubes over the diode plate end of the alternators to try to keep them cool, but they haven't been run yet to see if the cooling is adequate.
Has anyone else dealt with this?
Thanks,
John
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nuckolls.bob(at)aeroelect
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| Posted: Tue May 11, 2010 10:59 am Post subject: Alternator cooling |
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At 12:23 PM 5/11/2010, you wrote:
| Quote: |
After scouring the archives and only one post on topic, I come to
you all with an Alternator cooling question.
My alternators are driven off a spur gear and hence turn opposite to
their intended direction. I've built fiberglass "caps" with blast
tubes over the diode plate end of the alternators to try to keep
them cool, but they haven't been run yet to see if the cooling is adequate.
Has anyone else dealt with this?
|
. . . and if they had, their stories are probably
of limited or no value.
Cooling studies are always accomplished on an installation-
by-installation, model-by-model basis. Then the cooling
studies are blessed as 'golden' because type certificated
aircraft are configuration managed . . . you don't change
ANYTHING without due consideration for unintended consequences.
The ONLY way to ascertain your particular alternator cooling
requirements are to do max angle of climb, full electrical
load cooling studies with thermocouples attached to the
alternator's expected hot spots. After the test data is gathered
and averaged (over 5 or more climb profiles) you then correct the
measured temperatures for hot-day climate conditions.
Failures of alternators on OBAM aircraft due to inadequate
cooling are rare. Major contributors to this rarity are
light loading of alternators, minimum durations for heavy
loads, plenty of air-flow in vicinity of alternator, and
to some degree, luck.
You've obviously 'worried' about it enough to craft
specifically tailored cooling components . . . but
are still unsure. I suspect it's because nobody has repeated
your experiment before and there's no data to share.
So if you're really compelled to know, then you'll
need to fit thermocouples to your alternators bearing
mounts, diode heat sink, and perhaps a couple places
in the stator windings. You'll also need to fit your
airplane with a load bank you can adjust to set up
a nameplate rated load on the alternator along with
instrumentation to read alternator voltage, current,
and thermocouple temperatures. Then you get somebody
to fly with you to do the flight tests.
Once this data is acquired, then YOU will have become
the expert for whether or not your worries were justified
and extra ordinary cooling measures were necessary and
useful.
Bob . . .
Bob . . .
////
(o o)
===========o00o=(_)=o00o=========
< Go ahead, make my day . . . >
< show me where I'm wrong. >
=================================
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