Experimental Verification of Radial-Air-Gap-Type Permanent-Magnet-Free Synchronous Motor Utilizing Space Harmonics with Auxiliary Poles

Abstract

This paper describes a synchronous motor in which space harmonic power is utilized for the field magnetization instead of permanent magnets. The stator has a concentrated winding structure, and the rotor has two different types of windings, i.e., an induction pole (I-pole) winding that primarily retrieves the second space harmonic and an excitation pole (E-pole) winding for the field magnetization. The two coils are connected via a center-tapped full-bridge diode-rectifying circuit. The adjustable-speed drive characteristics and efficiency map are experimentally verified with a prototype motor. In addition, it is experimentally clarified that the field magnet function of the self-excited electromagnet pole has passive variableness with respect to the armature current, the rotation speed, the phase angle, and the time harmonics superimposed on the phase current. Furthermore, the drive performance of the proposed motor is studied by comparing the torque and efficiency characteristics.