High-Torque-Density Single Tooth-Wound Bar Conductor Permanent-Magnet Motor for Electric Two Wheeler Application

Abstract

The design of an in-wheel direct-drive motor for electric and hybrid electric two wheelers is studied, with particular focus on the use of bar-wound conductors in stator. In serving the space-constrained design problem of simultaneously achieving conflicting objectives of weight, cost, and short-term torque rating, this paper aims at comparing machines equipped with bar-wound stators with multistrand wound machines. This paper proposes different conductor shapes and arrangements that combine the advantages of fractional slot concentrated windings with bar conductors and describes the special fabrication method adopted for semiclosed slot geometry. The implications of using bar conductors on eddy effects and thermal equivalent circuit of the motor are studied and characterized experimentally. Finally, to investigate the impact of bar windings over multistranded windings on the ultimate performance metrics, a design study is conducted using a multiobjective optimizer for the two cases, and the resulting Pareto optimal sets are compared. The concept of the bar conductor tooth-wound motor is tested on a laboratory prototype, and the test results for skin effect, thermal contact resistance, and load tests are presented.