Alternator won't self excite help?

I have a 5KW power plant that powers my cabin. This week-end no
voltage came up when started. With limited tools and no volt meter I
invested. The brushes are in contact with the slip rings, I used a
light bulb and a 12 volt source to check the diodes and was able to
charge and discharge the capacitor across the brushes. The windings
are not shorted or grounded. Finally after nothing was found I
momentarily jumped 12 volts to the brushes and excitation was instant.
The genny ran 2kw of lights on my fishing pier all night. I figure
that the voltage output is normal because my battery chargers in the
cabin charged at the same amp rate as usual, as well there was no
flicker of lights. The problem remains that when the plant is shut
down and restarted it requires a jump start to the exciter brushes and
then it will produce again.
This is a simple circuit using only two poles in the field for the
main line output, and two poles that are center tapped to produce the
exciter source of 120v. Exciter voltage is rectified full wave by two
diodes and filtered by a capacitor to be fed to the rotor through the
brushes. Though all of this seems to work it will not come up on
excitation when started.
I will return next week to my cabin with better tools and a meter to
investigate further. Any one have any ideas what my have suddenly
caused such a condition? I work in the field of electrical controls
but this one has me stumped. Any help would be appreciated.
Thanks Bruce Buchanan
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Bruce Buchanan
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I haven't the fainted idea, but I remember a thread on about this. Try a search.
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