Design of a high fill factor permanent magnet integrated starter generator with compressed stator windings

This paper focuses on the improved thermal performance of electrical machines by increasing the conductor fill factor. A comparative design study of integrated starter generator (ISG) considering different pole/slot combinations and magnet topologies is used as a case study to fix slot dimensions. Compressed stator windings coupled with segmented stator structure are introduced to reduce copper losses of the optimized ISG. By performing quasi-static explicit dynamic simulations, deformation of insulation has been investigated regarding mechanical properties of the magnet wire enamels. It is noted that magnet wires at certain cross-sectional area can be compressed up to 0.72 fill factor without observing insulation failure. Thermal conductivity enhancement of the stator windings at improved slot fill factor is demonstrated by performing steady state and transient finite element thermal simulations.

I. Introduction

Electrification of the automotive sector has received great interest recently as it may represent a way of significantly reducing road traffic emissions. Electric vehicles can be classified as hybrid, fully electric, or range extended electric, each having its own unique requirements for the electric machine designer. Most automotive companies are working in at least one of these areas and some already have a marketable product.