Flux linkage maps identification of synchronous AC motors under controlled thermal conditions

This paper describes a flux linkage maps identification method for AC synchronous motors under thermal quasi-steady state operating conditions, corresponding to a specified machine rms current. This method applies to any synchronous machine, including Permanent Magnet (PM), wound field and synchronous reluctance machines. If the machine uses permanent magnets, then the proposed method allows the comparison of the machine performance for cold and hot conditions due to the influence of temperature on the magnets strength. The proposed method is implemented with inverter supply using the standard set of sensors that are normally on board of any industrial inverter. Nevertheless, augmented accuracy can be achieved when the identification method is implemented using a high-precision, external data recording device capable of collecting the motor voltages and currents, and the rotor position. The paper reports the experimental flux maps for an internal permanent magnet machine and a comprehensive comparison between the machine performance for cold and hot conditions, including the sensorless operation capability using high frequency injection.