A NEW DOUBLY SALIENT PERMANENT MAGNET MOTOR FOR ADJUSTABLE SPEED DRIVES

ABSTRACT

A new type of doubly salient motor is presented in this paper in which the field excitation is provided by permanent magnets. This doubly salient Permanent Magnet (DSPM) motor is shown to be kindred to square waveform permanet magnet brushless dc (PM-BLDC) motors in principle. However, they are different from the latter in that they are capable of a considerable constant power range when properly designed. Finite Element Analysis and Transient Simulation studies are utilized to investigate the characteristics of this new type of PM motor. A prototype DSPM motor is designed and comparison is made between this new type of motor and other types of motor on the basis of performance of the entire drive. By fully exploiting the merits of modern high energy PM material and the doubly salient structure, the DSPM motor can offer higher performance expectation over many existing motors in terms of efficiency, torque density, torque-to-current ratio, torque-to-inertia ratio etc. with a relatively simple structure which is amenable to automatic manufacture.