Restart Method for Induction Motor Drive System without Speed Sensor

Abstract

This paper proposes a restart method for an induction motor drive system without speed sensor after power supply interruption, when the motor shaft is rotaring under the action of disturbance torque. This method is based on the characteristic of the induction motor impedance, which is resonant for a frequency corresponding to the angular rotor speed. Positive feedback is used in the proposed method, in order to excite the natural frequency of the system and the speed information is extracted from the resonant stator cuurent. Since high speed ACR are not required, this method can be implemented using a low cost processor.
The validity of the proposed method is verified by simulation and experiments, using a standard 5.5kW induction motor.