Fast calculation of harmonic torque pulsations in a VSI/induction motor drive

The authors present a frequency-domain model for the accurate and efficient prediction of harmonic torque pulsations in three-phase VSI/induction motor drives, which enables rapid consideration to be given to their potentially harmful effects in producing uneven shaft rotation. A detailed analysis is provided for both quasi-square wave (QSW) and optimal pulse-width modulated (PWM) modes of switching operation, with the latter technique designed to improve the low-speed drive performance by eliminating low-order harmonic components. A comparison is made with practical results obtained from an experimental 0.56 kW drive and from a comprehensive time-domain model using a numerical solution of the machine equations. It is shown that accurate prediction of the actual performance is provided.<>