Identifying the Influence of Skin Effects on PWM-Induced Partial Discharges

Recurring, steep voltage pulses characterized by periodic polarity changes applied to electric motors or magnetic component windings are gaining prominence due to the increasing power electronics interfaced systems. The rising and falling edges of these high-frequency voltage waves can significantly influence their electrical properties, such as skin effects, and potentially have an impact on partial discharge (PD) characteristics. This study delves into the effect of the slope of voltage pulses on the skin effect and PD behavior in power electronics systems. The pulsating nature of power electronically switching voltage waves involves high-frequency components that lead to skin effects, a phenomenon that concentrates current density near conductor surfaces. It can lead to localized heating, higher electric fields, and increased insulation stress, which can change PD characteristics, including PD magnitude, rate, and inception voltage. We hypothesize that decreasing the voltage slope reduces its frequency content, potentially reducing the detrimental effects of skin effect and enhancing the insulation’s resistance to PD. Here, we also hypothesize that conductors with a thickness close to the skin depth should be immune to skin effects and hence exhibit lower susceptibility to PD. We investigated these two hypotheses by numerically simulating electric fields with COMSOL multiphysics software suit and validated them with real-world PD experiments. This observed finding directly supports the theoretical framework linking pulse shape and skin depth to electric field distributions, validating the effectiveness of a combined approach to PD mitigation, encompassing both optimized pulse shaping techniques and strategic conductor selection based on the calculated skin depth. By combining these two strategies, we aim to equip power electronic systems with enhanced resilience against PD, ultimately leading to improved reliability and extended operational lifespans