Flux-density space-harmonics minimization for an axial-flux permanent-magnet machine

The content of flux-density space-harmonics in axial-flux permanent-magnet machines (AFPMMs) is an important concern to the machine designer due to its impact on machine performances. In AFPMMs, the space-harmonics are related to the flux-density and the MMF distributions in the airgap, which are mainly determined by the PM excitation. This paper proposes two different approaches to study the flux density in the airgap. The finite-element and analytical methods are jointly developed in order to model and compare the flux density waveforms. Many optimization methods have been proposed in order to optimize the design of PM machines. In this paper, the authors investigate the optimal PM design in order to minimize the space-harmonics distribution using the sequential quadratic programming (SQP) optimization algorithm. By selecting the appropriate PM shape and size, it is possible to remove the undesirable harmonics. Using the SQP, the PM shape is optimized, and the harmonics content is notably reduced. The optimal solutions given by the FE model are then validated.