A High-Frequency Pulsating Signal Injection Technique for Surface Permanent Magnet Synchronous Motors

Pulsating High Frequency (HF) signal injection is a sensorless rotor position detection technique that uses magnetic saliency to detect rotor position during both starting and low speed operation of Interior Permanent Magnet Synchronous Motors (IPMSMs). However, this technique fails to work on Surface Permanent Magnet Synchronous Motors (SPMSMs) under all load conditions due to lack of magnetic saliency. To overcome this drawback, this paper proposes an extended pulsating HF technique in which an artificial saliency is created by changing flux in the d axis, based on the knowledge of the load applied on the motor shaft. The consequent variation of the d and q axis inductances introduces sufficient magnetic saliency to detect the rotor position at all load conditions. Experimental results are presented to prove the validity of the proposed technique.