Computation of Electric Field in e-Machines Using Finite Element Analysis - Leakage Current and Simulation of an AC Hi-Pot Test

This paper presents a comprehensive approach to computing the electric field in electric machines using finite element analysis (FEA), with a focus on the computation of leakage current through alternative current (AC) high-potential (Hi-Pot) excitation. The distribution of electric field in the machine's insulation system was calculated, and the possibility of insulation failure due to high magnitude electric field concentrations was discussed. The proposed FEA methodology provided a computationally efficient and accurate means of predicting the electric field distribution. This is extremely significant in a design and optimization of an electric machine, especially in automotive applications where power density, efficiency, and reliability are critical. The electric field distribution within a proposed interior permanent magnet (IPM) machine was calculated, under a Hi-Pot test of 1000 Volt-RMS AC, using a one-machine slot model to simulate a Hi-Pot insulation test. The maximum value of electric field in machine insulation was 8 kV/mm, with a leakage current of 10.1 mA average. This value fell below the standard corona initiation threshold of 14.5 kV/mm for slot liner STRATA3-200 insulators with high electrical insulation qualities. This indicated that the examined machine design was likely to withstand the high-potential test without premature breakdown due to corona effects.