Estimation of saturation characteristic of induction motors by injecting sinusoidal currents with customized low frequency

To keep ac magnetized state of iron core same as actual working condition and use steady-state information, a novel method for saturation characteristic estimation of induction motors at stand-still is proposed. The saturated mutual inductance is estimated according to measured stator-side reactance, when a low-frequency sinusoidal current is injected in single-phase mode. The frequency of sinusoidal current is customized according to the rotor time constant, which is a key point for successful estimation. Besides, no voltage sensor is included by using a voltage compensation technique, suitable for hardware setup of common inverters. Both simulation and experiments have been implemented to demonstrate the feasibility and validity of the proposed method.