Fast Initial Speed Estimation for Induction Motors in the Low-Speed Range

In this paper, a fast initial speed estimation method has been proposed for low rotational speed operation of speed sensorless induction motor drives based on the second-order differential of the secondary flux. The fast estimation can reduce an undesirable disturbance torque generation during the restart process. The effectiveness of the proposed method is confirmed by experiments. The estimation time has been compared with those in the literature and the benefit of the proposed method is confirmed.