Abstract: A method and system for characterizing a state of health of a winding of an electric machine are provided. The winding may include one or more stator windings in an electric machine, for example, a permanent magnet synchronous machine (PMSM). The method comprises: applying a voltage pulse to the winding; measuring a phase current signal of a current supplied to the winding; determining a high-frequency transient current based on the phase current signal. The state of health of the winding may be calculated as a function of change in frequency spectrum of the high-frequency transient current. The method may include calculating a plurality of packets using a wavelet packet decomposition of the high-frequency transient current; and determining one or both of: the state of health or a classification of degradation, using an indicator based upon at least one packet of the plurality of packets.

Abstract: A method and system for online monitoring and compensation of inter-turn short circuit faults (ISF) in windings of electric machines, such as permanent magnet synchronous motors is provided. A method for characterizing an ISF in a winding of an electric machine comprises: measuring phase voltages and currents; calculating sequence components of the electric machine based on the phase voltages and currents; determining a ratio between a percentage of shorted turns in the winding and a fault loop resistance based on the sequence components of the electric machine; and estimating characteristics of the inter-turn short circuit fault using an unscented Kalman filter. The characteristics include at least one of: a fault current, the percentage of shorted turns, or the fault loop resistance. A method for compensation an ISF in a winding of an electric machine comprises compensating the fault current based on the compensation current estimated from an unscented Kalman filter.

Abstract: Permanent magnet (PM) flux strength in a permanent magnet synchronous machine (PMSM) can be affected by operating conditions including thermal, mechanical, environmental and electrical stresses. Reduced flux strength, also called demagnetization, can lead to the degradation of the efficiency, performance and reliability of the machine and the drive system. A reliable PM strength, PM flux linkage, PM SOH, PM demagnetization detection method using the same inverter (i.e. motor drive) used to operate the PMSM is provided. The method comprises applying phase voltages to each of a plurality of motor leads of the PMSM with the PMSM at a stand-still condition; measuring current in each of the plurality of motor leads of the PMSM while applying the phase voltages thereto; and determining at least one of flux linkage, PM strength, PM SoH, or PM demagnetization based on a value of the current in at least one of the motor leads.

Abstract: A multilevel power converter, or inverter, for converting a direct current electrical power to an alternating current electrical power includes one or more 2-level converters each including gallium nitride (GaN) transistors configured to switch two input lines to a three-phase output line. The multilevel power converter may be used in a motor drive circuit, which may provide a 3-phase AC supply. Two power converters, which may be 2-level or 3-level power converters, may be alternately switched to provide the AC power to an AC motor by an output stage including bi-directional switching transistors configured to switch a corresponding three-phase output lines from the multilevel power converters. The multilevel power converters switch input lines from a neutral-point clamped input stage including capacitors connected in series across input terminals having a DC voltage therebetween to energize a midpoint terminal with an intermediate voltage half of the voltage between the input terminals.

Abstract: A motor drive for providing AC power to an electric motor includes a DC bus and three output terminals for connection to the electric motor. A positive switch selectively connects a positive conductor of the DC bus with each of the output terminals and a negative switch selectively connects a negative conductor of the DC bus with each of the output terminals. Each of the switches are Gallium Nitride (GaN) power switches. A controller commands each of the switches at a high switching speed between 10 kHz and 100 kHz using pulse width modulation to approximate an AC waveform on each of the output terminals. A dead time between activation of corresponding two of the switches conn to be selected to minimize a fifth-order harmonic distortion current.