Analytical modeling of the pulsation torque of an induction motor under Steinmetz circuit

Three-phase voltage unbalance has long been a problem in electric power system. It not only increases the system losses but has detrimental effects on three-phase rotating machines. This paper deals with the pulsating torque of an induction motor caused by Steinmetz connection which has been used for a three-phase motor operating on a single-phase supply. An analytical model based on the positive-sequence and negative sequence equivalent circuits of the motor is developed, and the pulsating torque as a function of the capacitance and slip rate are then derived. The proposed analytical method is verified by the Universal Machine Model of the EMTP. Finally it is provided to show the relation between site measurement, mathematical analysis and EMTP simulation. It is expected that the proposed method can be used to get a solution for pulsating torque by Three-phase voltage unbalance.