DC Link Capacitor Size Reduction Using Phase-Shifted PWM Techniques for Pole Phase Modulated Induction Machine Drive

Multiphase machines i.e. electrical machines with more than three phases have many advantages compared to the three-phase machines for high power density applications. The major advantages of multiphase machines include lower space harmonics thereby reduced losses and improved efficiency, reduced torque pulsations leading to lesser vibrations and acoustical noise, higher fault tolerance which retains the self-starting ability with minimum deration in the output power in case of fault in one or more phases and enhancement of torque density by adding higher order harmonic currents into the stator currents. Requirement of power electronic switches with reduced rating compared three phase motor drives for a given power rating is another important advantage which supports employing multiphase machines in high power applications. Wider speed and torque ranges are other important requirements of a drive for high power traction and propulsion application. Conventional machines need to be over-sized to achieve extended speed torque ranges which results in large volume, weight, high cost, and low efficiency. Pole changing techniques saves oversizing of machines by providing wider speed and torque variations maintaining constant power operation. In earlier days pole changing by reconfigurable stator windings using mechanical contactors were popular to achieve extended speed torque variations. The main drawback of these techniques is that reconfiguration of the stator windings for the next pole operations require de-energizing the stator windings from previous excitation. This affects the continuity in torque and motor operation. The pole phase modulation (PPM) of multiphase machines is a continuous pole changing technique wherein number of poles and phases of multiphase machine are varied in a particular ratio to achieve wider speed and torque ranges without the need of reconfiguring the stator winding connections. In PPM of multiphase machines, in particular multiphase induction motors (MIMs) the high pole mode supplies huge starting torque requirement of traction and propulsion applications for faster initial acceleration. The low pole mode of pole phase modulated multiphase induction motors (PPMMIMs) supplies high speed requirement for steady run of these applications. In this work, different pole phase combinations will be explored for Heavy duty vehicles