nuckolls.bob(at)aeroelect
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 Posted: Tue Feb 02, 2010 6:41 am Post subject: Using a SPST switch to control both the alternator field |
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At 11:50 AM 2/1/2010, you wrote:
Robert L. Nuckolls, III wrote:
> I have a switch that I really like that I want to use for the main
> switch. It's a heavy duty switch that can handle up to 75amp, but it's
> only a SPST switch.
Okay, WHY heavy duty? This switch normally carries
less than 5A for the alternator field and 1A for
the battery contactor. Since you're not attempting
to eliminate the battery contactor with a manual
switch, I'm mystified by the notion that trading
out the two pole master for a single pole device
is a good thing to do . . .
<snip>
Ok, so if I'm reading you right, since the battery lead on the alt and
the field lead are both connected to the main power bus, the residual
magnetism in the alternator could cause it to produce some bias
(voltage) that will keep the field coil working, which creates more bias
causing it to continue to work. Did I get that right?
Yes, that is the essence of "self excitation" . . . generators
did it nicely, alternators often do not come on line by themselves
but will run without a battery once they get stood up.
I wonder what happened to my attachment, I got it. Oh well, you can see
it here:
http://forum.matronics.com/viewtopic.php?t=67973
Anyway, no I'm not looking to replace the battery contactor.
Okay. That leads me to inquire as to the design
goals for departure from the legacy control philosophy
for a DC power master switch in aircraft.
No, I just like the switch (it's a push/pull), and it just happens to be
high current, I'll still use the contactor.
If it's just a style-thing, I'll suggest you reconsider
and go with Z-11 (or other architecture) as published.
Bob . . .
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