Torque Performance Analysis of HDD Spindle Motors Based on Geometrical Interpretation

By visualizing the torque as an area enclosed by locus of magnet operating points in
B
-
H
plane, several surface mounted permanent magnet (SPM) motors with different pole/slot combinations for hard disk drive (HDD) spindle motors are analyzed to clarify their geometrical characteristics of the maximum torque area. Then, a simple and fast calculation algorithm of predicting the maximum torque is proposed based on the torque geometrical interpretation and its validity is verified through comparison with FEA results. In addition, optimum pole/slot combinations for modern HDD spindle motors are recommended from the view points of reducing vibration resource caused by cogging torque and increasing speed control accuracy.