Concept of a New Permanent Magnet Motor for Flux Weakening Operation and Analysis of the Motor using FEM

Abstract

In variable speed drive applications, both the constant torque (low speed) and constant power (flux weakening) operating modes are required. As the magnet flux of a permanent magnet motor is fixed, the air-gap flux weakening is accomplished by applying a large d-axis current to drive at high speed. Therefore, efficiency of the motor is low and the permanent magnet is demagnetized irreversibly.
In this paper, a new permanent magnet motor for flux weakening operation is proposed and the characteristics of the motor using a magnetic analysis are described. The new permanent magnet motor has a rotor mounting permanent magenets which are covered with a magnetic ring made of Fe-Si or SUS630. To evaluate no-load, load and flux weakening characteristics of the motors, the field analysis using a two dimensional finite element method has been performed.
The results of analysis are shown that the new permanent magnet motor performs to the wide speed range of 2 times a maximum speed of a conventional motor.