Design of rare earth magnet free traction motor

Abstract

The global climatic scenario is confronting a highly alarming state which has pressed the countries around the globe to implement thoughtful actions in this regard. Transportation sector, being the major contributors to environmental pollution has witnessed a radical revamp. The greenhouse gases present in the tail pipe emissions from the internal combustion engine (ICE) powered vehicles is one among the root causes for global warming. Additionally, the availability of fossil fuels is also limited which has posed a serious threat to the future of ICE powered vehicles. This has marked a resurgence in the automotive industry-electrification of vehicles. Traction motor forms the main constituent in electric vehicle. Commercially speaking the motor should be efficient, light weight and less costly so that the large-scale manufacturing turns out to be viable and successful. The key candidates that are being utilized in market as traction motor are: Interior permanent magnet synchronous motor (IPMSM) and Induction motor (IM). Reluctance motors are the less popular contenders. Although IPMSM's possess higher torque density, efficiency when compared to other motors the drastic increase in cost of rare earth magnets have paved the way for using rare earth magnet free traction motor. IM's are limited by the reduced efficiency which lead to excessive heating and lower bearing life. This chapter highlights the significance of switching to a rare earth magnet free traction motor and a brief comparison among the motor choices is also presented. Since in this machine the torque produced entirely depends on the reluctance mechanism, the appropriate design of the rotor is essential. Electromagnetic design of SynRM with different parameters influencing the design is described in detail. Electromagnetic analysis is performed by using finite element analysis (FEA) tool ANSYS Maxwell 2D. An overview of literature discussing the design aspects, torque ripple minimization is also highlighted. The complete performance curves of the machine along the entire speed range helps in visualizing the machine features. ANSYS Motor-CAD is utilized for obtaining the torque speed curve. The essential outcome from the chapter is that the design presented meets the efficiency target of 95%. The costing analysis presented along with the efficiency clearly depicts that SynRM proves to be a promising and strong competitor with reference to IPMSM's. The conclusion gives a comprehensive overview of the motor along with the advantages, disadvantages and the measures that can be utilized further to alleviate the demerits.