Cogging Torque Reduction of Spindle Motor for it Application

For precise speed control of spindle motor using permanent magnet for IT application, it is important to minimize cogging torque when designing the motor instead of control topologies. Methods/Statistical analysis The design method for reducing cogging torque of spindle motor is proposed by changing magnetization pattern of permanent magnets (PMs) on a rotor. In order to change the magnetization pattern of PMs, design parameters related to shape of magnetizing fixture are selected and optimized. Magnetization performance on magnetizing fixture and cogging torque of spindle motor are analyzed by using finite element method (FEM). Findings A spindle motor should be controlled with constant speed feedback control algorithm. However, cogging torque and torque ripple of the spindle motor give a bad effect on constant speed control. There are many researches on decreasing method of cogging torque by using optimal design on spindle motor itself. In the paper, optimal design on a magnetizer in order for magnetization of permanent magnets on the spindle rotor surface is proposed instead of changing design parameters of spindle motor. In the result, cogging torque is decreased by up to 90 per cent without designing the dimension variables of the spindle motor. Moreover, magnetizing process is analyzed by considering initial magnetization characteristics of permanent magnet by using FEM. Improvements/Applications: This technique can be used in permanent magnet motor for high precision IT application including robot, dron, and electronic devices such as hard disk.