Estimation Technique for Rotor Time Constant of Induction Machines During I/f Speed Control

This paper proposes a method for estimating the rotor time constant of induction motors in the rotation state when there is no position or speed sensor. Since rotor time constant is used for vector controls and sensorless drives, accurate rotor time constant is necessary for high-performance drives. The proposed method estimates the rotor time constant through the relationship between the stator current and the stator flux. The stator flux is obtained through a flux observer. I/f speed control was used to estimate the rotor time constant in the rotating state. The proposed estimation method was tested using a 3.7 kW squirrel cage induction motor.