A speed self-sensing method in starting of induction motors

This paper presents a self-sensing method for speed estimation during the starting transient of induction motors. For this, a speed estimation strategy for squirrel cage or wound rotor induction motor is proposed from the measurement of the stator currents. The estimation is made by tracking sequence components for each frequency of the rotor harmonics present in the stator currents. The speed estimation avoids the use of electromechanical sensors that are generally fragile and their installation is expensive. In order to validate the proposal, experimental results obtained in the laboratory on a squirrel cage induction motor are shown. Results showed that the proposed estimation strategy is a useful tool capable of improving induction motor starting conditions.