Design and analysis of a new doubly salient permanent magnet motor

This paper presents the design and analysis of a new doubly salient permanent magnet (DSPM) motor. The corresponding output power equation is analytically derived. The initial calculation of motor dimensions and parameters, namely, the core diameter, stack length, permanent magnet size, and winding turns, are also discussed. An 8/6-pole DSPM motor is designed and built for exemplification. Moreover, finite element analysis of this motor is carried out to investigate the magnetic field distribution at different rotor positions and load currents, in which the leakage flux outside the stator circumference of the DSPM motor is firstly taken into account. Hence, the characteristics of the proposed motor are deduced. Experimental results of the prototype are given to verify the theoretical analysis and to confirm its high efficiency.

I. Introduction

At present, there is an increasing tendency to consider brushless motors, namely, the permanent magnet (PM) brushless motor and the switched reluctance (SR) motor, for industrial and electric vehicle applications [1], [2]. The PM brushless motor offers the advantages of high power density and high efficiency. However, since its PMs are located in the rotor, this motor suffers from the possibility of irreversible demagnetization by high temperature operation or armature reaction flux. Also, the mechanical integrity of PMs in the rotor inhibits its application at high speeds. On the other hand, the SR motor takes the advantages of simple configuration and mechanical robustness. However, because of the absence of PMs, it generally offers lower efficiency and lower power density than the PM brushless motor. Recently, a new class of brushless motors, termed the doubly salient permanent magnet (DSPM) motor, has been introduced [3], [4]. This DSPM motor incorporates the merits of both the PM brushless motor and the SR motor. First, the corresponding PMs are located in the stator, eliminating the problems of irreversible demagnetization and mechanical instability, while retaining the merits of high efficiency and high power density. Second, the corresponding rotor is the same as that of the SR motor, hence, adopting the advantages of simple configuration and mechanical robustness.