Torque Ripple Reduction for Low Pole Variable Flux Reluctance Machine

Abstract

This paper investigates reducing torque ripple for four poles variable flux reluctance machine (VFRM). Magnetic flux linkage variations depend on the rotor position for 12/10 and 6/4 topologies are obtained using finite element analysis (FEA). Harmonic components of magnetic flux linkages of 12/10 and 6/4 topologies are investigated. Torque ripple of 12/10 VFRM topology is extremely low as magnitudes of harmonics of the magnetic flux linkage are quite low. However, the magnetic flux linkage of the 6/4 machine has high magnitude even harmonics, which causes a high torque ripple. A double-stator structure is used to eliminate even harmonics of flux linkage. Torque ripple is decreased significantly since even harmonics are eliminated. Also, the harmonic injection method is used to further reduce torque ripple for double-stator 6/4 VFRM. 6th harmonic is injected into the DC field current. The magnitude and phase angle of harmonics are defined by torque variation which is obtained by FEA.