An estimation method of rotation speed for minimizing speed variation on restarting of induction motor

For minimizing unstable operation of an induction motor during acceleration, a three phase voltage-fed inverter has to increase an output frequency from a rotating speed. This paper proposes a new restarting method of induction motor for minimizing speed variation on a transient state of building up the flux. This method estimates the rotating speed using rotor flux observer and back electromotive force (back-emf) signals when the inverter starts an induction motor. This proposed method is verified by a test set experimentally.