Impact of Saturation and Scaling on the Field Weakening Performance of an Interior PM Machine

Paper in proceeding, 2020

If magnetic saturation is neglected, powerful visual tools exist for understanding field weakening in interior permanent magnet machines (IPMs). However, saturation can severely reduce field weakening performance. This is of concern in electric vehicle propulsion, where compact machines operate short-term at high power over a wide speed range. This paper shows how finite element results, including saturation, can be interpreted in established visual tools. This aids deeper understanding of field weakening in IPMs with significant saturation. Further, scaling laws for finite element results are shown to preserve field weakening performance. This allows analysis of machine peak performance over a range of maximum currents, with varying saturation severity, while scaling ensures precise fulfilment of torque and power requirements. Ultimately, this combination of current variation and scaling can be used to identify the trade-off between inverter rating and machine volume, with finite element analysis accuracy, for any specific application and IPM geometry.