Inverter-fed Based Electrical Machine Stator Winding Moisture Condensation Detection

Presence of moisture in the stator windings of electrical machines increases the risk of insulation failure. Integrating humidity transducers into the system results in additional costs and fails to provide direct measurements of moisture levels within the stator windings. This paper proposes the use of the capacitive leakage currents generated by a conventional inverter commutation (i.e., square-wave pulses) whenever the machine is off to identify winding moisture condensation offline. This method helps prevent insulation failure during service without additional hardware and can be triggered automatically and remotely. It will be demonstrated that the presence of moisture condensation influences both the magnitude of the capacitive leakage current and its resonance frequency; both of them will serve as reliable indicators of moisture presence in the stator windings.