ABSTRACT

In the spindle motor, the permanent magnet is made of bonded neumodiumiron-boron. Unbalanced Magnetic Pull (UMP) is detrimental for the application of spindle motor as it produces acoustic noise and vibration. The quality control of components and production is critical for reducing UMP. This chapter examines the major factors that must be considered before selecting a motor for hard disk drive (HDD) spindle and addresses the Issues arising from these factors. The Electro-magnetic Interference affecting the electronics system of HDD is a key factor to be considered while selecting the spindle motor. The zero-crossings of the back- electromotive force waveform are widely used to detect the rotor position and to measure the speed of the spindle motor in HDD products. In HDDs, the disks for storing information are mounted on the shaft of the spindle motor, and they rotate together with the rotor of the motor.