Sensorless vector control of induction motor based on a flux compensation with application to hoist crane

A practical sensorless vector control method for an induction motor is developed. Basically, the authors obtain the angle of the reference frame from the stator flux estimates that are obtained through integrating v_s-R_si_s. But this involves errors, especially in the low frequency range. The authors develop compensation schemes for flux magnitude and flux angle. The magnitude compensating term is obtained from the current error, while the angle compensating term is obtained from the real and reactive power relation. The usefulness of the proposed scheme is successfully demonstrated with a 110 kW inverter system for 40 ton hoist crane which requires 100% torque at 2~3 Hz