Electromagnetic and thermal analyses of surface‐mounted permanent magnet motor with flux‐absorbing structure for enhancing overhang effect

Abstract

Robot joint drive motors require high‐torque and power densities due to their limited space. Surface mounted permanent magnet (SPM) motors are appropriate for a robot joint drive due to their advantages of ease of construction, high productivity, and high controllability. To utilise the limited space effectively, a rotor overhang structure (OS) is frequently used in SPM motors due the performance enhancement and simple fabrication. However, the OS effects do not increase linearly but converge when it becomes longer. To deal with problem, a flux‐absorbing structure (FAS), which can effectively improve the performances even in case of a quite long OS by forming an effective flux path between the OS and stator can be used. However, the FAS results in different electromagnetic and thermal characteristics. In particular, there have been few studies on the thermal characteristics of the FAS, which can change motor performance considerably. Hence, a lumped parameter thermal network (LPTN) which can effectively consider the heat sources and heat transfer characteristics influenced by the use of FAS, is proposed. The feasibility of the FAS and the usefulness of the proposed LPTN was verified experimentally. The presented analyses and results here can be utilised in various high‐torque‐density application.