Impact of the Voltage Waveform on Dielectric Strength of Transformer Insulation at 1–10 kHz

Abstract

In power-electronic transformers (PETs), the insulating materials are exposed to rectangular voltages of frequencies in the range of several kilohertz. Although the impact of frequency on dielectric strength has already been investigated, the impact of the voltage waveform is at present not well-known. To investigate the differences between rectangular and sinusoidal voltage stresses and thus the impact of the voltage waveform, breakdown tests are carried out on commercially available solid insulation materials. The results show that the effective dielectric strength for rectangular stresses is higher than that for sinusoidal stresses for all materials and frequencies investigated.