Determination and classification of electric motor winding insulation degradation

A method for characterizing a state of health of a winding of an electric machine, the method comprising:

• applying a voltage pulse to the winding;
• measuring a phase current signal corresponding to the voltage pulse;
• determining a high-frequency transient current based on the phase current signal;
• calculating a plurality of packets using a wavelet packet decomposition of the high-frequency transient current;
• and
• determining, using an indicator based on the plurality of packets, at least one of:
• the state of health or a classification of degradation based upon at least one packet of the plurality of packets.

A system for characterizing a state of health of a winding of an electric machine, the system comprising:

• an inverter configured to apply an AC voltage to the electric machine and to supply current to the electric machine;
• a current sensor configured to measure the current supplied to the electric machine;
• and
• a controller in functional communication with each of the inverter and the current sensor and configured to:
• command the inverter to apply a voltage pulse to the winding;
• determine, based on the supply current, a phase current signal corresponding to the voltage pulse;
• determine a high-frequency transient current based on the phase current signal;
• determine a frequency spectrum of the high-frequency transient current;
• and
• determine the state of health of the winding as a function of a change in the frequency spectrum of the high-frequency transient current, and
• wherein determining the state of health of the winding as the function of the change in the frequency spectrum further includes determining a difference between the frequency spectrum of the high-frequency transient current and a reference spectrum.