STEADY-STATE CONTROL OF AN INDUCTION-MOTOR BY ESTIMATION OF STATOR FLUX MAGNITUDE

A technique is presented for estimating the stator flux magnitude in an induction motor from the DC link current. The signal produced has a wide bandwidth and is used in a feedback control system that maintains the stator flux magnitude at any desired value. The steady-state performance of an induction motor controlled in this way is modelled and compared with practical results. No speed, flux, voltage or current transducers are mounted on the motor. The effect of temperature variation on winding resistance is compensated for by using saturation-induced harmonics to indicate errors between the parameters from the controller model and the real motor.