James H Nelson wrote:
> When trying to use a OV protection with the Rotax alternator you
> need to send the output from the Rotax through a relay. This relay is
> part of the OV control using "lectric Bob's" system. All you have to
> do is make sure that the output from the Rotax is connected to the
> 2500mfd capacitor all the time. This capacitor is the stabilizing
> "load" that must be on the output.
I think we need to be careful here. The only cause of overvoltage will
be a defective regulator. If OV protection opens the relay, thus also
removing load, there is potential to place AC voltage voltage across the
25,000uf Faraday device of maybe 100V P-P. The result will be one heck
of bomb shortly exploding within the airframe. If the regulator is
defective but all load disconnected, the capacitor simply isn't needed
to protect something which has failed. The relay should be placed
"upstream" of the capacitor.
> So my Rotax alternator is basically "just
> there" with no work being done. (Until my 40A goes "south").
We don't know what's inside the Rotax regulator, but the only way to
achieve what you describe is either a series regulator or "classic"
switching regulator, which the Rotax reg neither clearly is not. If
under no load, the regulator runs hot, power not used is being
dissipated therein. If cool, then there's some substantial portion of
250 watts dissipated in the generator coils, augmented by engine heat.
The only possible problem is that's within the same stator assembly
that's providing spark voltage! An AC ammeter inserted in the AC line
to the regulator will divulge the truth. Approximate current, as the
ammeter will read RMS voltage drop for an assumed sine wave, which the
generator output ain't (10-phase 1/2-wave?).
Regards,
Fred F.
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