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Synchronous Generator Avr


miki83

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Hello to all. Need some help if anyone has the time/will/knowledge I would greatly appreciate any comments.

 

We have a diesel genset with a synchronous generator of 55 kVA (general brochure can be found at www.vokvataeki.is/SeverCat/Generators.pdf, type DRE 365-4, 50Hz/1500 RPM, couldn't upload it, sorry) which is missing the AVR and drops the voltage when a bigger load is connected.

 

The exciter has a compound and a regulating field. The compound field is powered from a simple circuit board (still there and working OK as far as I know) with a rectifier and a couple of resistors, while the regulating field is, I think, supposed to be powered from the missing AVR. The problem is we don't have any documentation on the generator or the AVR but what little data can be found in the catalog. Also, the exciter's rated voltage and current are missing from the generator's nameplate. I've been looking for replacement AVR's on the net, but since my knowledge is rather limited here I have some concerns... :

 

1) If I understood correctly the regulating field should be using DC current? For a generator this size I understood that an AVR with a 5A rated output should do (rated current of the generator is 79.5 Amps)?

2) If the regulating field is current-fed does anyone have any idea what is the voltage I can expect? Found some AVR's that could go up to 100V, is this sufficient?

3) What kind of damage can occur on the generator if the AVR is not correctly chosen? I suppose if the current's too high I'll burn the AVR (or the internal fuse), so no harm done. What about voltage?

4) Would it be possible to temporarily power the regulating field of the exciter from the 24V DC battery with a potentiometer between the battery and the regulation winding? In this case we could change the excitation while connecting the loads gradually and we could measure the current needed to keep the constant voltage on full load so we could size the replacement AVR.

 

That would be about it for now. Thanks to anyone in advance :)

 

Best regards, Miki.

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