Automatic Inductance Measurements of Synchronous Reluctance Machines Including Cross-Saturation Using Real-time Systems

This paper presents a new approach to the inductance measurement of a synchronous reluctance machine. Instead of an open loop pulsed voltage reference described in many references, a pulsed current reference is applied to the test machine in closed loop. The response of the machine is measured, and voltage and current samples are processed (integration) in real time to calculate the flux linkages and inductances. Since the measurement is done in current control mode, the time constant of the overall system can be modified in such a way that a sufficient number of samples are available during the transient even for machines with smaller time constants. This improves the accuracy of the measurement for low time constant machines compared to the voltage reference based measurement. Additionally, inductance at a desired operating point is obtained in a single trial; this reduces the duration of the measurement process. Unlike the pulsed voltage reference method that requires post processing of a huge data set to calculate the inductance map of the machine, the proposed method can be programmed in a real time processor to automate the generation of an inductance map of the test machine.