Multiphase Machines and Drives-Revisited

Recent developments in the area of multiphase machines and drives are reviewed. The first survey focuses on the progress in power electronic supply control for multiphase systems and innovative ways of using the additional degrees of freedom in multiphase machines for various nontraditional purposes. Recent additions to the knowledge in relation to pulsewidth-modulation (PWM) control strategies in multiphase drives, using two-level and multilevel voltage source inverters in conjunction with a star-connected machine and an open-end winding configuration, are examined, and the quality of the obtained stator current and voltage waveforms is compared using the total harmonic distortion factors. The second survey discusses recent advances in the design, modeling, and control of multiphase machines, including the traditional uses of additional degrees of freedom to enhance the electrical torque using low-order stator current harmonic injection and to achieve fault-tolerant operation. A mathematical model for six-phase induction machines, based on the circuit-oriented approach, is presented in order to analyze the machine behavior in healthy and faulty operating conditions. Another paper addresses an entirely new application of the additional degrees of freedom offered by multiphase machines.