Recent experience has shown that early indication of the onset of internal coil failures in a stator winding can be detected by the use of rotor-mounted scanning infrared sensors. Prior to the implementation of the infrared scanning sensors, the common belief was that preceding a turn insulation failure, while there may be some arcing within the winding and the pyrolyzing of insulation, there was no significant detectable evidence of turn insulation degradation until it's too late. Even if the minute electrical discharges or pyrolysis particles were detected, there was no way to determine the location of the impending fault using these conventional methods; so the obvious result was an unexpected failure. With this paper, we will show two examples of early detection of impending internal coil failures that if acted on can allow time for repair before a failure damages core and coils.
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