Condition Monitoring of Stator Groundwall Insulation for AC Motors by Broadband Common-Mode Impedance Observation

Stator winding insulation is one of the most fragile components in electric drive system. To prevent insulation-related failures, online condition monitoring of stator insulation is critical to ensure high reliability requirements in inverter-fed ac motors. Groundwall insulation monitoring can be achieved by common-mode (CM) measuring methods, which evaluate insulation by CM impedance spectrum shifts. However, CM impedance shows distinct insulation-related characteristics over broadband frequency range. In this article, insulation-related characteristics are revealed and compared by developing individual models in different frequency regions. Besides, a hybrid model-data driven method is proposed to achieve assessment of groundwall insulation in this article. Phase-to-ground and neutral-to-ground insulation are distinguished by pretrained network, which establishes the link between CM features and insulation capacitances. Experimental results have been conducted on inverter-fed induction machine with an accelerated aging procedure. The experiment results prove that the proposed method can achieve detection of groundwall insulation in real time.