A method for correction of rotor time constant in indirect field orientation of an induction motor

This paper describes a method for the correction of rotor time constant due variations in the operating conditions of induction motor drives. In field oriented control, due to the variation of rotor time constant, decoupling between the flux and torque components of stator currents is lost and hence the operational performance of the machine deteriorates. This detuned operation is corrected by calculating stator flux signals with the help of stator voltages and stator currents in an indirect field orientation scheme having speed feedback. The error in the flux is used to adjust the gain of slip calculator until decoupling is achieved. This consequently improves the dynamic performance of the motor. The validity of this technique is verified through simulation studies on an induction motor