Modeling and performance of a 120° square-wave inverter/induction machine drive

Abstract This paper extends and enhances prior work on the 120° square-wave inverter/induction motor drive to include short periods of regeneration produced by torque pulsations. Particular attention is paid to the accurate calculation of the back e.m.f. of the open-circuited phase. A key feature of this work is the subdivision of the motor equations depending on the particular thyristors that are conducting. The above enhancements lead to improved accuracy (in the order of 20%) in the calculation of motor torque over previously published work. Theoretical predictions are verified by previously published measurements on a six-pole, three-phase, squirrel-cage induction motor producing a maximum motoring power of 185 kW.