Diagnostic method of induction motor stator winding interturn short circuit fault based on the feature impedance

A diagnostic method of induction motor stator winding interturn short circuit fault based on the feature impedance is proposed in this paper. The fundamental positive and negative sequence components of the voltage and current are separated effectively by the improved multiple reference frames theory and Hilbert transform, then the impedance matrix of the motor is calculated. Taking the fluctuation of the load, supply unbalance and the inherent asymmetry of the motor into account, the feature impedance Z(np) in the impedance matrix is selected as the stator winding interturn short circuit fault character, for its sensitivity and reliability. A series of experiments on a 4kW induction motor give the relationship between the amplitude of the feature impedance and the short circuit fault. Corresponding to the different input power, the fault diagnosis threshold and fault severity factor are set up. Experimental results demonstrate the effectiveness of this method.