Comprehensive analysis and evaluation of cogging torque in Axial Flux Permanent Magnet machines

Evaluation and minimization of cogging torque in Axial Flux Permanent Magnet (AFPM) machines become essential specially in direct drives for low speed applications. This paper presents a comprehensive analysis of the cogging torque in AFPM machines designed for low speed applications and mitigation methods are proposed. Evaluation methodologies of the cogging torque based on Finite Element Analysis (FEA) computations are discussed and applied to a double-sided, internal rotor, AFPM reference machine. From the performance comparison of Maxwell stress tensor and virtual work methods on the evaluation of cogging torque, it is possible to conclude that the latter overestimates the amplitude of the cogging torque into a considerable extent.