Overview

Focusing solely on magnetic design in the early stages of electrical machine development can result in costly rework due to temperatures, mechanical stress, or electric breakdown in the later phases. Multi-disciplinary evaluation solves this challenge. By simultaneously evaluating not only the magnetic performance but also the insulation, stress and temperature, designers can find an optimal design and lower the chance of any rework.
In this case study, we optimize a wound field synchronous motor (EESM) with two objective functions – average efficiency under the WLTC driving cycle and maximizing torque. Since cooling evaluation on the field coil side is essential for EESMs, we adopted a multi-disciplinary evaluation approach, considering field coil temperature, rotor stress, and the maximum electric field in the slot insulation paper. As a result, electric breakdown occurred even though one of the designs achieved both high efficiency and torque. This highlights the necessity of simultaneous multi-disciplinary evaluation to obtain optimal designs without rework.

Table 1. Multi-disciplinary Evaluation Indices

This case study focuses on optimizing a wound field synchronous motor (EESM), considering not only performance requirements, such as maximum torque and average efficiency during the driving cycle, but also multi-disciplinary evaluation criteria including field coil temperature, rotor stress, and the maximum electric field on the insulation paper.