AN OVERVIEW ON COGGING TORQUE AND TORQUE RIPPLE REDUCTION IN FLUX SWITCHING MACHINES

Udochukwu B. Akuru

Keywords

Cogging torque, finite element analyses (FEA), flux switching machine (FSM), permanent magnet (PM), torque ripple

Abstract

Flux switching machines (FSMs) have continued to receive wide interest among researchers in recent times, especially in terms of permanent magnet (PM) excited topologies. In the mid-1950s after it was first unearthed, FSMs did not gather enough momentum due to its very high PM material requirements, as well as the incipient nature of PM mining technologies, primitive computer-aided design capabilities and emerging power electronic drives, among others. Today, advances in these fields have made FSMs very researchable and technically viable. In addition, their high-torque density performance, along with a robust rotor structure, makes them very attractive. However, due to a double-salient nature, FSMs are susceptible to high cogging torque and torque ripples, which not only result in vibrations and audible noise but also can proceed to mechanical stress in their electrical drivetrains. To this end, many researchers are working to address these inherent problems using numerical analysis techniques, viz., finite element analysis, among others. The relevant studies are reviewed and discussed in this article, of which the recorded research on addressing cogging torque and torque ripple in FSMs is very overwhelming and commendable, while inadvertently occurring at the expense of depreciating torque density.

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