Incipient faults in inverter-driven permanent magnet machine drives can often be detected and their progression monitored by some characteristic parameter in the machine's modeling equations. Some diagnosis and prognosis methods use features not reflected in the machine model, evident when voltage and current frequency harmonics are used. To indicate an inverter fault, a model of the inverter is instead used and its characteristic parameters found to detect parametric changes. Insulation condition is assessed by monitoring the high-frequency slot capacitance and high slot resistance. Demagnetization faults are detected by monitoring changes in the inductance.In order to improve permanent magnet synchronous machine reliability, inverter faults must be detected in addition to motor faults. A minimally-invasive technique is developed which uses the device voltage-current characteristics. By detecting small changes in the voltage-current characteristic, each device's condition is assessed and the time to failure estimation is improved.The remnant flux density of one or more rotor magnets in a PMSM can be reduced, resulting in demagnetization which occurs from either over-temperatures or excessive demagnetizing current. A magnet with reduced remnant flux density also has a reduced coercivity--it is more susceptible to further reversible demagnetization. Voltage and current harmonics can detect the presence of demagnetization, but cannot differentiate between rotor eccentricity and demagnetization in all cases. The direct axis incremental inductance can also be used to indicate demagnetization because this can be used to detect a change in the saturation characteristic. Analysis is used to show the process of demagnetization.Stator winding insulation failure has the potential outcome of catastrophic failure, cessation of operation, or the necessity for mitigation. Insulation degradation is either caused by voltage stress across the insulation or insulation thermal cycling. Because insulation degradation is reflected in the insulation's electrical characteristics, a method is presented to assess the insulation with its equivalent resistance and capacitance. A method is shown to assess the insulation condition with currents present during switching transitions induced by high dV/dt.
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