On the Design of a Near-zero-speed Direct-driven Permanent Magnet Synchronous Torque Motor

With the speed and the back-EMF values approaching zero in super-low-speed direct-drive PMSMs, its design has great differences with those of common machines. This paper summarized the differences and presented the design guidelines of several key parameter selections and their influences on motor performances by theoretical analyses as well as FEA calculations. What's more, as the torque stability is crucial for achieving high position precisions, the MMF harmonic distributions of different pole-slot combinations and winding patterns were analyzed and were managed to constrain the torque ripples. By adopting certain pole-slot combination with properly designed winding patterns plus some harmonic MMF reduction techniques, the total torque ripple level can be constrained to minimum.