On Eliminating Heavy Rare-Earth PM Elements for High Power Density Traction Application Motors

Abstract

A high performance Interior Permanent Magnet (IPM) machine utilizing heavy rare-earth elements is considered the workhorse for many applications especially traction applications. Dysprosium (Dy) is one of the heavy rare-earth elements used in higher Permanent Magnet (PM) grades and its inclusion is critical to eliminate/minimize the risk of permanent demagnetization. On the other hand, Dy is one of the key elements that are subject to price volatility as well as sustainability concerns. Therefore, this paper aims to propose an IPM machine design for traction applications based on Nissan Leaf 2012 electric motor using a blend of magnet types that eliminate the use of Dy (can be thought of as hybrid magnets) to reduce the overall PM cost while maintaining comparable electromagnetic performance. Most importantly, this paper's objective is to provide a topology for the transportation sector using PM materials that addresses sustainability concerns. This paper will present the electromagnetic performance evaluation of the proposed design using Two-Dimensional Finite Element Analysis (2D-FEA). Comparison of key performance metrics including torque vs. current angle, efficiency map, risk of demagnetization, and comprehensive comparison to the baseline design will also be presented. In addition, rotor mechanical analysis as well as cost analysis are included.