Design and analysis of 4-phase (in-hub) mini-switched reluctance motor for spindle motor in hard disk drive

In present hard disk drive systems, the brushless DC motor is the spindle motor of choice. However, the higher cost of rare-earth permanent magnets and the complexity of its controller are some of its disadvantages. Its performance also deteriorates in small format disk drive systems. This paper proposes a four-phase (in-hub) miniature switched reluctance motor with an outer rotor structure for the spindle motor in a 3.5" hard disk drive. The design methodology of the mini-SR motor is described. The magnetic characteristics, flux linkage, inductance, coenergy and static torque, have been calculated using 2D finite element analysis. The field solutions and the analysis of an electric circuit have been processed to give the description of the dynamic-state performance of the prototype. With a suitable control strategy, the prototype of the four-phase (in-hub) mini-SR motor can meet the basic specifications of the spindle motor in 3.5" hard disk drives. The development of mini-SR motor provides an alternative spindle motor in hard disk drive systems