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 najurb

Reply to
Bruce Buchanan
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I haven't the fainted idea, but I remember a thread on alt.home.repair about this. Try a search.

Reply to
John

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