Electromagnetic design of permanent magnet motors for high speed applications

Permanent magnet (PM) electric motors supported by fluid bearings are often used in high-speed applications. One example is the use of such spindles in data storage devices such as modern hard disk drives. This paper focuses mainly on the electromagnetic design aspects for PM motors. A finite element based approach is devised to obtain accurate predictions of electromagnetic torque and forces (UMP). The paper also discusses the dynamic behaviours of the disk spindle system with the presence of the electromagnetic excitation forces that may drive the disks to resonance. It is found that UMP can have a significant effect on structural dynamics of the disk-spindle system