Three traction motors with different magnet materials — Influence on cost, losses, vehicle performance, energy use and environmental impact

Abstract

The aim of reducing both cost and environmental impact of automotive electric traction motors motivates the examination of motor performance when using magnets of varying strength and materials. Such investigations have attracted increasing interest in recent years. Given the same take-off torque capability, three motors are compared that have the same stator geometry but different magnet materials in the rotor; two PMSMs — one with Nd(Dy)FeB and one with SmCo magnets — and one PMaSynRM with strontium-ferrite magnets. To compensate the weaker magnets, their corresponding core stacks are prolonged. The resulting torque capability at high speed levels is lower for the SmCo PMSM and ferrite PMaSynRM compared to the Nd(Dy)FeB PMSM. The ferrite PMaSynRM has the poorest dynamic vehicle performance, but also the lowest energy losses over a wide range of drive cycles. In addition, the ferrite based motor option has the lowest environmental impact during manufacturing as well as the lowest material cost estimate. The SmCo motor has slightly lower losses than the Nd(Dy)FeB, but the highest material cost. Certainly, the result signals that further in-depth studies of the described PMaSynRM are of high relevance.