Impact of Interphase Dielectric Property on Electric Field Distribution of Polymer Nanocomposites

The fast-switching frequency, high slew rate, and high voltage provided by the advanced power electronics inverters promote pa discharge (PD) in the turn-to-turn insulation in the inverter-fed motors. Polymer nanocomposites have been drawing the attention of researchers as PD-resistant insulating materials in inverter-fed motors. The high-volume fraction of interphase between the metal oxide nanoparticles and polymers improves the dielectric properties of the enameled wire. In this article, a numerical model of the electric field distribution of polymer nanocomposites is developed based on the dielectric properties of the interphase between the nanoparticles and metal oxides. The relative permittivity of the interphase region is first determined from the thickness and volume fraction of nanoparticles. A numerical model of polymer nanocomposites is developed in COMSOL Multiphysics to determine the electric field distribution for various interphase relative permittivity driven by the volume fraction of nanoparticles and interphase thickness. This numerical model is useful in designing polymer composites to effectively mitigate PD in inverter-fed motor windings.

I. Introduction

The technological advancements in power electronics inverters have led to progress in the electrification of transportation. The fast-switching frequency, high voltage blocking capacity, and high efficiency provided by wide bandgap (WBG) semiconductor-based power electronic-driven systems enable designs with high gravimetric and volumetric power density [1], [2]. However, when the electric machines are fed by the PWM inverters with short rise time, impedance mismatch occurs at the motor terminal which generates a large voltage difference between the turns of the motor. This sudden increase in the voltage at the motor terminal increases the electrical stress in the insulation system and promotes partial discharge (PD) in the motor winding [3], [4], [5]. PD characteristic in the motor winding fed by the SiC-based power electronic inverter has drawn the attention of researchers from the last decade [6], [7]. The insulation materials used in enameled twisted pair wires are polymeric materials such as polyurethane, polyurethane resin, polyamide, polyester, and polyimide [8].