Development of a flux, speed and rotor time constant estimation scheme for the sensorless induction motor drive

The paper presents a control scheme for the sensorless induction motor that yields the estimates of the fluxes, motor speed and inverse of the rotor time constant. The motor is field-oriented using Direct Field Orientation — the stationary frame fluxes are obtained from a combined Current and Voltage Model Observer. The speed is obtained from a flux-based MRAS sliding mode observer. More importantly, the rotor time constant inverse is estimated from a sliding mode observer using a simple dynamic model. The availability of the rotor time constant improves the speed estimation accuracy and allows implementation of a more robust sensorless control scheme.