Page 88 - Basic PD Theory
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References
IR 1(min) = minimum insulation resistance of the entire machine winding in megohms, at 40 C
o
kV= rated machine terminal to terminal voltage, in rms kilovolts
13. Endwinding Vibration Response
Especially for large 2 and 4 pole stators, it is necessary to determine slackness in end winding bracing, blocking and ties. Use
calibrated hammer, accelerometers and frequency analyzer to look for high amplitudes and resonance at 100/120 Hz.
Finds: endwinding vibration problems
14. Winding Resistance
Use a Wheatstone bridge to measure the winding’s copper resistance between phase leads or the resistance of each phase. For medium to high
voltage, form windings of all phase readings should be within 1% of each other. Higher resistance in one phase indicates open coils or poor
connection or joints. Low resistance may be indicative of shorted turns. Any changes in trend should be investigated, but comparisons should
only be made when the measurements were made at the same temperature.
Finds: shorted turns and high-resistive connections
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