An Analytical Model of Unbalanced Magnetic Force in Fractional-Slot Surface-Mounted Permanent Magnet Machines

We present an analytical model of unbalanced magnetic force (UMF) in fractional-slot surface-mounted permanent magnet (PM) machines having diametrically asymmetrical winding distribution but no static/dynamic rotor eccentricities. It is based on a 2-D analytical field model and accounts for the influence of both the radial and tangential force waves under any load condition. It is capable of providing insight into the generation, harmonic contents, and characteristics of the UMF and accurately predicting the magnitudes, rotation directions, phase angles of its harmonics and various components, such as the UMFs due to armature reaction only, mutual interaction between both PM and armature reaction fields, and radial and tangential force waves. The cancellation and additive effects between the UMF components resulting from the radial and tangential force waves are revealed for the first time by the analytical model. We show that such effects strongly depend on the UMF harmonic order, slot/pole number combinations, and the internal/external rotor machine topologies. We have validated the analytical model by finite-element analyses and partially by experimental results.

[1]  Z. Zhu,et al.  Instantaneous magnetic field distribution in brushless permanent magnet DC motors. I. Open-circuit field , 1993 .

[2]  Z. Zhu,et al.  Instantaneous magnetic field distribution in brushless permanent magnet DC motors. II. Armature-reaction field , 1993 .

[3]  Z. Zhu,et al.  Instantaneous magnetic field distribution in permanent magnet brushless DC motors. IV. Magnetic field on load , 1993 .

[4]  Z. Zhu,et al.  Instantaneous magnetic field distribution in brushless permanent magnet DC motors. III. Effect of stator slotting , 1993 .

[5]  A.C. Smith,et al.  Calculation of UMP in induction motors with series or parallel winding connections , 1994, IEEE Power Engineering Review.

[6]  N. Schirle,et al.  History and trends in the development of motorized spindles for hard disk drives , 1996 .

[7]  G. Jang,et al.  Torque and unbalanced magnetic force in a rotational unsymmetric brushless DC motors , 1996 .

[8]  S. X. Chen,et al.  Design trends of spindle motors for high performance hard disk drives , 1996 .

[9]  D. G. Dorrell,et al.  Calculation and measurement of unbalanced magnetic pull in cage induction motors with eccentric rotors. I. Analytical model , 1996 .

[10]  Zhejie Liu,et al.  Analysis of Unbalanced-Magnetic-Pulls in hard disk drive spindle motors using a hybrid method , 1996 .

[11]  Liu Zhejie,et al.  Effects of unbalanced magnetic pull in spindle motors , 1997 .

[12]  S. X. Chen,et al.  Design Of Fluid Bearing Spindle Motors With Controlled Unbalanced Magnetic Forces , 1997 .

[13]  Byung-il Kwon,et al.  Influence on brushless DC motor performance due to unsymmetric magnetization distribution in permanent magnet , 2000 .

[14]  Sang-Moon Hwang,et al.  Comparison of vibration sources between symmetric and asymmetric HDD spindle motors with rotor eccentricity , 2000, Conference Record of the 2000 IEEE Industry Applications Conference. Thirty-Fifth IAS Annual Meeting and World Conference on Industrial Applications of Electrical Energy (Cat. No.00CH37129).

[15]  No-Gill Park,et al.  Analysis of vibration for permanent magnet motors considering mechanical and magnetic coupling effects , 2000 .

[16]  Weui-Bong Jeong,et al.  Effect of rotor eccentricity on spindle vibration in magnetically symmetric and asymmetric BLDC motors , 2001, ISIE 2001. 2001 IEEE International Symposium on Industrial Electronics Proceedings (Cat. No.01TH8570).

[17]  Z. Zhu,et al.  Improved analytical model for predicting the magnetic field distribution in brushless permanent-magnet machines , 2002 .

[18]  S.M. Jang,et al.  Analysis of unbalance force for high speed slotless permanent magnet machine with Halbach array , 2003, Digest of INTERMAG 2003. International Magnetics Conference (Cat. No.03CH37401).

[19]  Taeyong Yoon.  Magnetically induced vibration in a permanent-magnet brushless DC motor with symmetric pole-slot configuration , 2005, IEEE Transactions on Magnetics.

[20]  Chao Bi,et al.  Unbalanced-magnetic-pull induced by the EM structure of PM spindle motor , 2005, 2005 International Conference on Electrical Machines and Systems.

[21]  U. Kim,et al.  Effects of magnetically induced vibration force in brushless permanent-magnet motors , 2005, IEEE Transactions on Magnetics.

[22]  Chao Bi,et al.  Influence of Drive Current to Unbalanced-Magnetic-Pull in Spindle Motor , 2006, Asia-Pacific Magnetic Recording Conference 2006.

[23]  A. Arkkio,et al.  Comparison of the Unbalanced Magnetic Pull Mitigation by the Parallel Paths in the Stator and Rotor Windings , 2007, IEEE Transactions on Magnetics.

[24]  Chao Bi,et al.  Unbalanced magnetic pull induced by drive current in PM-BLDC motor operation , 2007, 2007 International Conference on Electrical Machines and Systems (ICEMS).

[25]  Z.Q. Zhu,et al.  Unbalanced Magnetic Forces in Permanent-Magnet Brushless Machines With Diametrically Asymmetric Phase Windings , 2005, IEEE Transactions on Industry Applications.

[26]  Dan M. Ionel,et al.  Unbalanced Magnetic Pull in Fractional-Slot Brushless PM Motors , 2008, 2008 IEEE Industry Applications Society Annual Meeting.

[27]  G. Jang,et al.  Experimental Measurement and Simulated Verification of the Unbalanced Magnetic Force in Brushless DC Motors , 2008, IEEE Transactions on Magnetics.

[28]  Z. Q. Zhu,et al.  Influence of slot and pole number combination on radial force and vibration modes in fractional slot PM brushless machines having single- and double-layer windings , 2009, 2009 IEEE Energy Conversion Congress and Exposition.

[29]  M. Hsieh,et al.  Unbalanced Magnet Pull in Large Brushless Rare-Earth Permanent Magnet Motors With Rotor Eccentricity , 2009, IEEE Transactions on Magnetics.