Surface-Permanent-Magnet Synchronous Machine Design for Saliency-Tracking Self-Sensing Position Estimation at Zero and Low Speeds

Elimination of externally mounted position sensors and their associated cables is a goal for drive manufacturers. This paper addresses design methods of surface-permanent-magnet (SPM) synchronous machines for saliency-tracking self-sensing (position sensorless) position estimation. Machine spatial saliency is created by stator magnetic saturation due to the rotor zigzag leakage flux from SPMs. Using the machine saliency created by zigzag leakage flux can allow an SPM machine to be suitable for saliency-tracking position estimation without the need of any special rotor design modification. In addition, another major benefit is achieved, i.e., a saliency role reversal whereby L-d > L-q. This has the advantage of reducing machine cross-saturation and increasing the feasible region for closed-loop self-sensing control. All the design procedures are verified by the finite-element analysis, and a 50-W SPM machine is used for experimental evaluation.