SPM Motor Operation with High Frequency Signal Injection Technique: Failures and Causes

Pulsating High Frequency (HF) signal injection technique is one of the sensorless position detection methods. It has demonstrated high accuracy in estimating the rotor position in Permanent Magnet Synchronous Motor (PMSM) drives. However, this technique, which uses magnetic saliency to detect the rotor position, fails to detect the rotor position in Surface Permanent Magnet Synchronous Motors (SPMSMs) under loaded conditions. Therefore, this paper investigates the causes of the rotor position detection failure in SPMSMs. The paper discusses two components that could contribute to an offset error in rotor position estimation, which in turn leads to a failure in the motor operation under loaded conditions. The two offset errors are identified as the time delay in the Low Pass Filter (LPF) used in the rotor position detection loop and the changes in the motor parameters under loaded conditions. Simulation results are presented to show that there exists a correlation between the offset error and the nominal inductance variation factor when the motor is loaded.