A novel current-injected sensorless control scheme for squirrel-cage induction motors

This paper presents a novel sensorless control scheme of squirrel-cage induction motors by using a PWM waveform injection technique for the estimation of rotor dependent stator leakage inductances. To increase the signal-to-noise ratio when operating in low-speed region, the magnitude of the injected signal is adaptively adjusted according to motor operating condition. Practical realization issues of the detection of the reflected signals and estimation of the rotor position have been addressed. The developed sensorless control scheme has been implemented by using a high-performance single-chip DSP controller. Experimental verification of the developed adaptive injection scheme and rotor position estimation scheme has been carried out. Experimental results show the proposed sensorless position control scheme can reach a position control resolution of 0.05 rad with a rated holding torque.