One method for indirect speed estimation in vector controlled induction machine drive

In order to improve the robustness of vector controlled induction machine drive, the direct speed measurement should not be applied. One method for indirect speed estimation, which permits speed estimation from the stator voltage equation in field coordinates is introduced. Presumptions that the rotor flux vector modulus is held constant and total leakage factor is considered to be zero are used. The speed estimator is applied to the indirect field orientation control structure. Simulation results and experimental verification on a 4 kW drive show that good behaviour is obtained in static conditions under variable load and in dynamic conditions under stepwise speed reference changes. The dynamic and static performances are still acceptable even if error in assumed values for stator and rotor resistance exists. The parallel control unit contains two digital signal processors in working in the inverter is realized with IGBTs.