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Back-EMF ZCP error induced by EM structure of spindle motor

In a hard disk drive (HDD), the zero crossing points (ZCPs) of back-emf generated in the spindle motor armature windings are used as rotor position signal for realizing precision motor speed control. The error of ZCP is thus very concerned in HDD products, especial for the HDDs with ultrahigh data recording density. In the paper, several reasons inducing the ZCP error are analyzed, and these reasons are from the problems in the motor design and production. Both the analytical and numerical methods are used in the analysis to analyze the influence of the electromagnetic structure to the ZCP. The related solutions are proposed to reduce the errors of the ZCP in the motor design.