Magnetizing Curve Identification for Induction Motors at Standstill Without Assumption of Analytical Curve Functions

It is necessary to obtain accurate knowledge about the magnetizing curve of an induction machine so that the magnetizing inductance can be updated according to different flux references for either efficiency optimization or field weakening control. This paper proposes a computational saving method to obtain a one-to-one correspondence magnetizing curve without the need for conventional curve-fitting strategies, which require the assumption of explicit analytical curve functions. A detailed comparison between the proposed method and the conventional curve-fitting method has been done. It shows great accuracy improvements of this proposed method. The identification is easy to implement with high precision while maintaining the motor at standstill. No additional sensor devices are needed except the sensors carried by the drive itself. This proposed method is verified by simulation. Further experimental results of this method are utilized in a real control strategy with a 2.2-kW 50-Hz 4-pole induction motor to confirm its validity and feasibility.