Relation between space charge accumulation and partial discharge activity in enameled wires under PWM-like voltage waveforms

TLDR

Voltage waveforms from power electronic converters significantly affect electric motor insulation reliability, with partial discharges identified as the main degradation mechanism, prompting the development of new enamel magnet wire insulations and aging‑test characterizations to estimate life under varied stress conditions. The study investigates the relationship between aging phenomena induced by supply voltage waveforms and partial discharge activity, presenting experimental evidence linking discharge parameters to electrical properties and space‑charge accumulation. The authors propose a methodology that characterizes and compares insulating materials for power‑electronic waveforms, enabling evaluation of candidate materials. The approach provides manufacturers with feedback on additive composition and enamel components for magnet wires in power‑electronic motors.

Abstract

It has been observed that voltage waveforms generated by power electronic converters may affect significantly the reliability of electric motor insulation. Since partial discharges are considered to be the main cause of the reliability loss, new enamel insulations for magnet wires are being developed in order to withstand better stress amplification. The electrical characterization of these insulating materials is often carried out through aging tests which may provide estimation of life under different stress levels and conditions. However, deeper investigation of aging phenomena due to supply voltage waveforms is needed, especially regarding the relation between aging factors and stress conditions. This paper deals with this topic, showing experimental evidences of relation between partial discharge quantities (e.g., inception voltage, repetition frequency, amplitude) and electrical properties, associated with charge accumulation, which can be directly evaluated through space charge measurements. Characterization of insulating materials and comparison of materials candidate for application in power electronic waveform environment can be carried out resorting to the methodology proposed here. This approach can provide, therefore, a useful feedback to wire manufacturers regarding, e.g., the choice of additive nature and enamel components for magnet wires in power-electronic controlled motors.