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Old 03-02-2015, 03:01 PM   #1
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Default Generator Problem

Hi

I got this generator that have been working fine until yesterday. The generator when started works fine, but after 3 minutes the voltage drops from 230vac to 150-70vac and fluctuate. I have tried to replace the AVR with a new one but still i have the same problem. What do you guys think the problem could be ???


This is some info on the generator

40KW
3 Phase
50HZ
Brushless alternator
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Old 03-02-2015, 03:17 PM   #2
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Could it be a bad alternator?
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Old 03-02-2015, 03:23 PM   #3
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Is the engine rpm steady?
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Old 03-02-2015, 03:24 PM   #4
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Quote:
Originally Posted by Dennis Alwon View Post
Could it be a bad alternator?
Dennis;

I have tested both the exciter winding and the main stator winding and both have their resistance up to specs
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Old 03-02-2015, 03:29 PM   #5
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Well my guess was the voltage regulator but it sounds like you replaced that already. Not sure what else if everything else is in tact
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Old 03-02-2015, 03:44 PM   #6
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Quote:
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Is the engine rpm steady?
Yes its steady
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Old 03-02-2015, 04:07 PM   #7
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post your question over on "smokstak.com lot of great mines over there on all types of generators. lot of smart ones here also!
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Old 03-02-2015, 04:38 PM   #8
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First thing I would do is call the manufacturer and see if tech support could offer if any some answers.
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Old 03-02-2015, 07:45 PM   #9
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where in Dubai is it ? I wonder if ISIS snuck in during the night and put a potato in the exhaust.
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Old 03-02-2015, 07:59 PM   #10
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Check "all" your connections. Loose wire could cause the VR to wander.
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Old 03-02-2015, 10:38 PM   #11
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Def check for loose connections at the source and first means of disconnect.
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Old 03-02-2015, 11:35 PM   #12
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Quote:
Originally Posted by magmash View Post
Dennis;

I have tested both the exciter winding and the main stator winding and both have their resistance up to specs
Straight resistance measurements will not always detect
shorted turns or insulation breaking down under load.

You need to do a ring test for that.

And a megger test.
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Old 03-02-2015, 11:58 PM   #13
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Are you taking these readings with a load on it?
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Old 03-03-2015, 12:11 AM   #14
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Have you done a load test on the rotating diodes ?. One possible theory could be that a diode or two fails during load and causes a not constat current flow to the electro magnet from the exciter, which would cause the generator to output a fluctuating voltage + reduced voltage.
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