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460V Motor failed on DC Hi-Pot test 1
- Thread starter HamidEle
- Start date
Dear Mr. HamidEle (Electrical)(OP)18 Mar 20 03:02
1. " FYI, the vendor came back and recommended to use 500v to Meggaer 460v motor as it is not ...."
Agreed.
Reference: (Megger an instrument manufacturer) states that commonly used test voltage for routine maintenance for equipment rating 440-550Vac , the test voltage is 500-1000Vdc.
2. Insulation resistance value taken with 1000Vdc may differ from the value taken with 500Vdc with the same duration and temperature. They do not indicate any defect if both readings are above the generally minimum acceptable resistance value.
3. In practice, a 460Vac motor [should be able],(without any ill effect) to be tested at !000Vdc.
4. Although testing a 460Vac motor at 500Vdc seems to be low, while testing it at 1000Vdc seems to be better, but NOT necessary.
Che Kuan Yau (Singapore)
1. " FYI, the vendor came back and recommended to use 500v to Meggaer 460v motor as it is not ...."
Agreed.
Reference: (Megger an instrument manufacturer) states that commonly used test voltage for routine maintenance for equipment rating 440-550Vac , the test voltage is 500-1000Vdc.
2. Insulation resistance value taken with 1000Vdc may differ from the value taken with 500Vdc with the same duration and temperature. They do not indicate any defect if both readings are above the generally minimum acceptable resistance value.
3. In practice, a 460Vac motor [should be able],(without any ill effect) to be tested at !000Vdc.
4. Although testing a 460Vac motor at 500Vdc seems to be low, while testing it at 1000Vdc seems to be better, but NOT necessary.
Che Kuan Yau (Singapore)
LionelHutz
Electrical
megger is slang for a megohmmeter testing.
Based on talks with an individual from an old school motor shop I deal with, I would surge comparison test a questionable motor myself with no derating for it being a used motor.
Based on talks with an individual from an old school motor shop I deal with, I would surge comparison test a questionable motor myself with no derating for it being a used motor.
- Thread starter
- #23
Hamid
As I said, the winding connection is not recognized by standards for hipot tests. The test is based on the rated voltage, not phase to ground voltage. The idea of maintenance test is to assure the motor is good for service. Better to have a test failure under controlled circumstances than to have a service failure, which leads to more expensive shutdowns and possibly more expensive damages to repair. Do the tests as per standards not as per vendor's fears.
Muthu
As I said, the winding connection is not recognized by standards for hipot tests. The test is based on the rated voltage, not phase to ground voltage. The idea of maintenance test is to assure the motor is good for service. Better to have a test failure under controlled circumstances than to have a service failure, which leads to more expensive shutdowns and possibly more expensive damages to repair. Do the tests as per standards not as per vendor's fears.
Muthu
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