The breakdown characteristics of thermostable insulation materials under high-frequency square waveform

Breakdown tests on four types of thermostable inter-turn insulation material were carried out under bipolar high-frequency square waves from 1~20 kHz. The insulation breakdown voltage under different frequencies were determined from the two-parameter Weibull distribution. The voltage life characteristic was calculated based on the inverse power function model. The relationship between insulation thickness and breakdown voltage at high frequencies was also studied. The results show that, the characteristic breakdown voltage, decreases with increasing frequency, and reaches a maximum at 1~5 kHz. The voltage life characteristic curves shift with increasing frequency and thermal breakdown is the main cause for failure. At high frequencies, the non-uniform electric field and heat causes the breakdown voltage to change nonlinearly, and increased frequency increases this non-linearity.