Tests on rewound generator
Tests on rewound generator
(OP)
We are going to carry out the following tests on a 1800kVA 440V Generator: (stator windings were newly rewound)
1. Insulation Resistance and Polarization Index test
2. DC Resistance test of windings
3. No load output voltage with separate excitation and record excitation voltage and current.
4. Check vibration value and bearing temperature.
What are the acceptable values for all the above tests?
1. Insulation Resistance and Polarization Index test
2. DC Resistance test of windings
3. No load output voltage with separate excitation and record excitation voltage and current.
4. Check vibration value and bearing temperature.
What are the acceptable values for all the above tests?






RE: Tests on rewound generator
IR > 100 megohms & PI>2
Vibration < 2.5 mm/sec peak
Bearing Temp < 80 deg C
Muthu
www.edison.co.in
RE: Tests on rewound generator
Did you perform a loop test on the core before it was rewound to check for lamination shorts in the stator? I don't believe you can do this with the unit rewound, but I could be wrong.
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If it is broken, fix it. If it isn't broken, I'll soon fix that.
RE: Tests on rewound generator
TurbineGen, could you please explain how a loop test is carried out. The stator was found badly burnt at end windings.
RE: Tests on rewound generator
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RE: Tests on rewound generator
You then let the stator heat up from the magnetization (10 minutes is plenty) and take pictures of the thermal image. The more precise the thermal camera, the better. Hot spots indicate there is likely a short between stator laminations. You can then repair the shorted laminations by inserting an insulating medium between the laminations, or occasionally using phosphoric acid and a DC current works too. I've done both with excellent success.
------------------------------------------------------------------------
If it is broken, fix it. If it isn't broken, I'll soon fix that.
RE: Tests on rewound generator
TurbineGen, thanks for explaining what loop test is. After it is rewound, is there any other tests we can carry out to determine there is any short between stator lamination?
RE: Tests on rewound generator
This is just an engineer's educated guess. I've never tried it to see if it would actually work. I've always done the loop test with the stator windings removed.
If the damage was found at the end windings I'd suspect an insulation issue. Stator shorts cause excessive heating to the windings inside the stator slots. It doesn't usually affect the end turns.
------------------------------------------------------------------------
If it is broken, fix it. If it isn't broken, I'll soon fix that.
RE: Tests on rewound generator
I need to check back the scopes involved for the first rewinding job.
RE: Tests on rewound generator
Since it has been rewound now, you could do ELCID test to on the wound stator to check the core health. In my opinion, ELCID is inferior compared to full flux loop test described above but it has been gaining a credibility in the past decade.
Muthu
www.edison.co.in