Torque Performance Improvement with Modified Rotor Winding Circuit of Wound-Field Synchronous Motor Self-Excited by Space Harmonics

Abstract

This paper describes a synchronous motor in which space harmonic power is utilized for 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 field magnetization. The two coils are connected via a center-tapped full-bridge diode rectifying circuit. The optimum placement of the I-pole on the rotor is mathematically discussed and is analytically determined through FEM-based computer simulations. In addition, it is clarified that the E-pole torque increases owing to the effect of auxiliary poles. Further, the advantages of auxiliary poles are studied, using the torque ripple characteristics.