Insulation life-span models for electrical and thermal aging under continuous high square impulses voltage

Stator insulation of inverter-fed motors experiences continuous impulses with significant harmonics and transients, which may result in early failure. There are many differences in insulation aging mechanism between under continuous impulses and sine waves. In order to test insulation properties under continuous impulses, a new insulation aging test system is used to simulate the aging effect of converter on the winding insulation in the inverter-fed motors. The influences of multi-stress including impulse amplitude-temperature, impulse frequency-temperature and impulse frequency-amplitude on insulation lifetime are investigated. And the test data under different conditions are analyzed by the statistic analysis method of Weibull distribution. Finally, insulation life models for multi-stress is developed based on the above test results, which is helpful for the insulation design of inverter-fed motor.