Multi-phase motors have several advantages over the traditional three-phase motors.In this study, the additional degrees of freedom available in five-phase permanentmagnet motors have been used for three purposes: 1) enhancing the torque producingcapability of the motor, 2) improving the reliability of the system, and 3) better adjustingof the torque and flux linkages of the five-phase direct torque controlled system.1) Due to the fact that space and time harmonics of the same orders will contributepositively to output torque, a five-phase permanent magnet motor with quasi-rectangularback-EMF waveform is supplied with combined fundamental and third harmonic ofcurrents. For modeling and analysis of the motor a 0 3 3 1 1 q d q d frame of reference isdefined where 1 1q d rotates at the synchronous speed and 3 3q d rotates at the three timessynchronous speed. Based on the mathematical model in the 0 3 3 1 1 q d q d frame ofreference, it is shown that this system while having a higher torque density with respectto a conventional permanent magnet synchronous machine, is also compatible withvector control algorithm.2) A resilient current control of the five-phase permanent motor with both sinusoidaland trapezoidal back-EMF waveforms under asymmetrical fault condition is proposed.In this scheme, the stator MMF is kept unchanged during healthy and faulty condition.Therefore, the five-phase permanent magnet motor operates continuously and steadilywithout additional hardware and just by modifying the control algorithm in case of lossof up to two phases. The feature is of major importance in some specific applicationswhere high reliability is required.3) High torque and flux ripple are the major drawbacks of a three-phase directtorque controlled system. The number of space voltage vectors directly influences theperformance of DTC system. A five-phase drive, while benefiting from other advantagesof high order phase drives, has inherently 32 space voltage vectors which permits betterflexibility in selecting the switching states and finer adjustment of flux and torque. Asensorless direct torque control of five-phase permanent magnet motor is implemented.Speed information is obtained based on the position of stator flux linkages and loadangle.Experiments have been conducted on a 5kW five-phase surface mount permanentmagnet motor and a 3kW five-phase interior permanent magnet motor by usingTMS320C32 DSP. The results obtained are consistent with theoretical studies andsimulation analysis, which further demonstrate the feasibility and practical significanceof the five-phase permanent magnet motor drives.
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