Influence of Winding Structure and the Effect of MMF Harmonics to the Spindle Motor Performance for Ultrahigh TPI HDD

The technologies for maintaining high recording density to suppress mechanical vibration and media flutter for ultrahigh TPI hard disk drive (HDD) require advance spindle motor design and technology against the traditional norms. To realize multimagnetic poles with limited stator slots, spindle motors generally use concentrated windings which offer small end winding and simple structure suitable for mass production. There is a variety of ways to construct a motor with different winding structures based on different pole/slot combinations. Winding structures directly affect the producing of motor back-emf and torque which determine motor capacity, reliability and efficiency. In this work, detailed analysis is carried out to identify the optimal winding structures of the high speed spindle motor and analyze their effect on the motor performances by using magneto-motive force harmonics analysis and electromagnetic magnetic field analysis. Results are useful in preliminary and final optimal designs of the high speed spindle motors.