A novel stator resistance estimation method for speed-sensorless induction motor drives

A method for online estimation of the stator resistance of an induction machine is presented and a speed-sensorless field-oriented drive equipped with the proposed estimator is built. The drive is particularly suitable for low-speed operation. Resistance estimation is based on a two-time-scale approach, and the error between measured and observed current is used for parameter tuning. The simple full-order observer in use allows for direct field orientation in a wide range of operation. The system can drive active load and generate stall torque, as confirmed by numerical simulations and experimental tests on a general-purpose 7.5 kW induction machine.