Uneven Inter-turn Voltage Distribution among Windings of Medium-voltage Medium/High-frequency Transformers

摘要

Working under PWM pulse voltage, medium voltage medium/high-frequency transformers may face unevenly distributed electrical stress between inter-turns. This could increase the probability of partial discharge in the winding insulation and thus the risk of premature insulation failure would be higher. To investigate this issue, an equivalent circuit model of a transformer's winding is built. Based on that, simulations on voltage distribution between inter-turns with different voltage rise times, frequencies, material relative permittivity, insulation distance, and number of turns are conducted. The results show that uneven voltage distribution exists in the winding of transformers operating under PWM pulse voltage, with the first two turns suffering from the highest voltage drop. Also, the influence of the above-mentioned parameters on the inter-turn voltage distribution is revealed.