SPMSM Design Considerations for Initial Position and Magnet Polarity Estimation using Carrier Signal Injection

Initial position and magnet polarity estimation is required for smooth start-up of permanent magnet synchronous machines. The signal-to-noise ratio of the salient signals used for initial position and magnet polarity estimation depends on the machine design and affects the overall performance of the estimation technique. This paper investigates the design of a ring-magnet, surface permanent magnet synchronous machine to maximize the signal-to-noise ratio of the position and polarity signals without compromising the machine performance. Since the rotor geometry is fixed given the ring-magnet, the effect of the stator tooth tip geometry on the saliency signals is evaluated using finite element analysis. By adding a bridge between the stator teeth, the magnitude of the polarity-based signal can be increased significantly. A coupled simulation verifies the implementation of the improved initial position and magnet polarity estimation based on modified machine design.