Optimum Flux-Weakening Characteristics for Five-Phase Surface Mount Permanent Magnet Synchronous Machines

This paper aims to explore the effect of varying the motor drive parameters on the optimum flux-weakening performance of the Multi-Frequency (MF) five-phase surface mount permanent magnet synchronous motor drive (MF five-phase SPM). A lossless, steady-state per-unit, DQ model is presented. The flux-weakening performance of the Single Frequency (SF) five-phase surface mount permanent magnet synchronous motor (SF five-phase SPM) is considered first because it represents a simplified case of the MF five-phase SPM drive and gives an insight into the operation of the MF five-phase SPM motor drive. Only the fundamental and the third harmonics are assumed to be in the spectrum of the back electromotive force (EMF) and are considered as the torque producing terms in the first plane and the second plane respectively. A new DQ normalisation for an MF five-phase SPM drive, based on the rated quantities of the first DQ plane, is developed to be used in the optimisation process necessary for studying the effect of varying the motor parameters on the flux weakening performance. The non-linear optimisation problem that aims to maximise the electromagnetic torque of the MF five-phase SPM machine under the voltage and current constraints, for operation in the linear modulation region, is formulated.