Title :
Frequency Characteristics of BEMF, Cogging Torque and UMF in a HDD Spindle Motor due to Unevenly Magnetized PM
Author :
Kang, K.J. ; Jang, Gun Hee ; Sung, S.J.
Author_Institution :
Dept. of Mech. Eng., Hanyang Univ., Seoul, South Korea
Abstract :
This research mathematically derives the frequency equations of back electromotive force (BEMF), cogging torque and unbalanced magnetic force (UMF) of a brushless DC (BLDC) motor due to unevenly magnetized permanent magnet (PM). The proposed mathematical equations are experimentally validated by comparing with the measured BEMF, cogging torque and UMF of a hard disk drive (HDD) spindle motor with 12 poles and 9 slots (12P9S). Only 3-multiple harmonics originated from uneven magnetization of the PM in the spindle motor with 12P9S introduce same frequency components to BEMF and slot-multiple harmonics to cogging torque, respectively. However, other harmonics of the uneven magnetization of PM except the 3-multiple harmonics introduce slot-multiple ±1 harmonics to UMF.
Keywords :
brushless DC motors; disc drives; electric potential; hard discs; magnetic forces; magnetisation; permanent magnet motors; permanent magnets; torque; 3-multiple harmonics; back electromotive force; brushless DC motor; cogging torque; frequency characteristics; frequency components; frequency equations; hard disk drive spindle motor; mathematical equations; slot-multiple harmonics; unbalanced magnetic force; uneven magnetization harmonics; unevenly magnetized permanent magnet; BEMF; UMF; cogging torque; magnetization;
Journal_Title :
Magnetics, IEEE Transactions on
DOI :
10.1109/TMAG.2013.2245317
