Partial discharge characteristics of piezoelectric ceramics under bipolar and unipolar applied voltages

Electrical partial discharge measurement has been investigated as a nondestructive test method to evaluate the mechanical reliability of piezoelectric ceramics. In order to understand the factors affecting partial discharge in piezoelectric ceramics, the effect of electric loading conditions is investigated. In this work, electrical partial discharge tests have been carried out on piezoelectric bulk ceramics under electric loading in both bipolar and unipolar modes. Partial discharge inception fields are measured for piezoelectric ceramic samples. The results demonstrate that under bipolar sinusoidal applied voltage, electrical partial discharges tend to occur at relatively low electric fields as compared to the case of unipolar field application. This suggests that the partial discharge recurrence rate may be lower under the unipolar applied voltage. Besides, the polarization change during domain switching under bipolar waveform in piezoelectric ceramics may facilitate partial discharges.