Design of a single-sided axial flux PM in-wheel electric vehicle machine with non-overlap stator windings

[摘要] ENGLISH ABSTRACT: With the current worldwide energy problems electric vehicles are set to replace conventional combustion engine vehicles. Electric vehicles with gearless in-wheel mounted brushless permanent magnet motors provide a more flexible and efficient means of vehicle propulsion but the electric motors, particularly the non-overlap stator winding type have not been fully researched.This study focuses on the selection and design of suitable in-wheel hub drive machine. Several machine topologies are evaluated and the single-sided axial flux machine is chosen. The average vehicle requirements are determined and design optimisations are carried with the aid of finite element analysis and an optimisation algorithm. A comparison of torque quality between single-layer and double-layer machines is carried out and it is found that double-layer machines have the least torque ripple and single-layer machines with un-equal teeth the best torque per ripple characteristics. A 16 kW, 30-pole 27-slot prototype machine optimised for power density is built, and it is found fitting for the application meeting the design requirements. The prototype machine is extensively tested and good agreement is found between finite element and measured results. The well known axial flux attraction forces are encountered in the prototype machine and they are overcome by suitable bearing selection and mechanical design. It is found that theoretical and measured cogging torques are inconsistent, the reason for this is that practical machines are not absolutely ideal due to material and manufacturing tolerances. Excessive rotor losses are found in the prototype machine and appropriate methods for their reduction are presented. This work does not aim to find the best in-wheel hub drive solution, but instead looks to uncover some of the technical available solutions.

[发布机构] Stellenbosch University