Operating characteristics of adjustable-field permanent magnet motors with 3D magnetic paths and asymmetric magnet arrangement

This paper describes a three-dimensional structure and a high-power density rotor structure using asymmetric permanent magnet (PM) arrangement of an adjustable-field PM motor aiming to achieve both high-torque and high-efficiency operations in a high-speed and low-torque range. It is demonstrated by 3D-FEA that it is possible to achieve the adjustable-field operation without sacrificing the high-torque density. In addition, the adjustable-field effect was verified through an experimental no-load test by measuring some induced voltages of a prototype motor based on the proposed method.