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This research presents a finite element method to analyze the electromechanical field of a hydrodynamic-bearing (HDB) spindle motor of computer hard disk drives at elevated temperature. Magnetic field is analyzed by the nonlinear time-stepping finite element method considering the switching action of PWM inverter, and magnetic force and torque are calculated by the Maxwell stress tensor. Mechanical motion of a rotor is determined by Newton's equation of motion, in which the hydrodynamic bearing force and friction torque are calculated by solving the Reynolds equation. Both the analyses of magnetic and mechanical field are combined in a closed loop to control the speed using PWM. Simulation results are verified by the experiments. This research also investigates the electromechanical performance of a HDB spindle motor at elevated operating temperature.
Date of Publication: July 2004