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Author Topic: lister SR3 15 HP 1500 with Dunlite 10 KVA Alternator. Problem of interest.  (Read 5396 times)

kingull

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This unit has Datatronics controller for the engine. Protects, engine and also the alternator (if no volts is detected).
I experienced what appeared to be a big short circuit where generator no longer gave output.

Restarts with the datatronics controller would recycle every few seconds with no volts detected.
All windings had continuity and no earth faullts apparent.
A big learning curve for me.

I disconnected the Datatronic controller from the generator terminals.
Prepared it to connect to AC mains for testing purposes.
Hit the datatronics start button then enegised the Datatronics controller from mains after about one second.
Generator came back online and ran normally.

Thob

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I'll take a wild guess at it -

The engine was shut down during the short circuit event, allowing the generator to slow down and stop under the short circuit, which mostly demagnetized the generator.  With very little residual magnetism, it took several seconds for the generator to create enough voltage for it's exciter to produce enough current to run the main generator, resulting in no voltage out until you were able to run the engine for a while.  Once it gets going again, it should re-magnetize and work OK.

You may need a way to manually "flash" the field (put some DC current thru the field to re-establish the residual magnetism).

Like I said - a wild guess.
Witte 98RC Gas burner - Kubota D600 w/ST7.5KW head.
I'm not afraid to take anything apart.
I am sometimes afraid I'm not going to get it back together.

kingull

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Was a good guess and the generator is up and running again.
Seems the AVR dropped out as the load was excessive (Air conditioner plus all sorts of other appliances).
The Datatronics controller did not allow enough time for the AVR to reset (Just a guess).
I connected the avr to mains power and fired up the engine. The alternator came alive again.
Big relief and thanks for your theories.