Reduction of Cogging Torque in Double-Rotor Axial-Flux Permanent-Magnet Disk Motors: A Review of Cost-Effective Magnet-Skewing Techniques With Experimental Verification

Minimizing cogging torque in designing axial-flux permanent-magnet (AFPM) motors is one of the main issues which must be considered during the design process. This paper presents several cost-effective magnet-skewing techniques to minimize cogging torque components in double-rotor AFPM motors. Rotor-side cogging torque minimization methods are examined in detail with major focus on magnet-skewing approach, and several cost-effective alternative skewing techniques are proposed. A detailed comparison of magnet-skewing approaches is provided. A prototype AFPM motor with different rotor structures is built based on the analyses. Analyses are then validated with experimental results, and the influence of cogging torque component on torque quality of AFPM motors is explored. The results confirm that the proposed magnet-skewing approaches can significantly reduce the cogging component as opposed to reference AFPM motor with unskewed magnets and help to improve the torque quality of the disk motors.

[1]  Thomas M. Jahns,et al.  Pulsating torque minimization techniques for permanent magnet AC motor drives-a review , 1996, IEEE Trans. Ind. Electron..

[2]  D. Howe,et al.  Influence of design parameters on cogging torque in permanent magnet machines , 1997, 1997 IEEE International Electric Machines and Drives Conference Record.

[3]  Z. Zhu,et al.  Influence of Electric Loading and Magnetic Saturation on Cogging Torque, Back-EMF and Torque Ripple of PM Machines , 2012, IEEE Transactions on Magnetics.

[4]  M. Aydin,et al.  Magnet shape optimization of A slotted surface-mounted axial gap PM motor for reducing cogging torque , 2010, The XIX International Conference on Electrical Machines - ICEM 2010.

[5]  D. Staton,et al.  Comparison of Analytical Models of Cogging Torque in Surface-Mounted PM Machines , 2012, IEEE Transactions on Industrial Electronics.

[6]  Thomas A. Lipo,et al.  Cogging torque minimization technique for multiple-rotor, axial-flux, surface-mounted-PM motors: alternating magnet pole-arcs in facing rotors , 2003, 38th IAS Annual Meeting on Conference Record of the Industry Applications Conference, 2003..

[7]  J.A. Tapia,et al.  Design Consideration to Reduce Cogging Torque in Axial Flux Permanent-Magnet Machines , 2007, IEEE Transactions on Magnetics.

[8]  Z. Zhu,et al.  Investigation of Torque Ripples in Permanent Magnet Synchronous Machines With Skewing , 2013, IEEE Transactions on Magnetics.

[9]  M.A. Valenzuela,et al.  Axial flux PM machine design with optimum magnet shape for constant power region capability , 2008, 2008 18th International Conference on Electrical Machines.

[10]  Nicola Bianchi,et al.  Design techniques for reducing the cogging torque in surface-mounted PM motors , 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).

[11]  R. Bojoi,et al.  Direct Flux Vector Control of Axial Flux IPM Motors for in-wheel traction solutions , 2010, IECON 2010 - 36th Annual Conference on IEEE Industrial Electronics Society.

[12]  Il-Woo Kim,et al.  Cogging Torque Optimization of Axial Flux Permanent Magnet Motor , 2013, IEEE Transactions on Magnetics.

[13]  T. Miller,et al.  Prediction of cogging torque using the flux-MMF diagram technique , 1995, IAS '95. Conference Record of the 1995 IEEE Industry Applications Conference Thirtieth IAS Annual Meeting.

[14]  Thomas A. Lipo,et al.  Torque quality and comparison of internal and external rotor axial flux surface-magnet disc machines , 2006, IEEE Transactions on Industrial Electronics.

[15]  C.C. Chan,et al.  Axial-Field Electrical Machines - Design and Applications , 1987, IEEE Transactions on Energy Conversion.

[16]  M.A. Valenzuela,et al.  Cogging Torque Reduction in an Axial Flux PM Machine via Stator Slot Displacement and Skewing , 2007, IEEE Transactions on Industry Applications.

[17]  Hoang Le-Huy,et al.  Minimization of Torque Ripple in Brushless DC Motor Drives , 1986, IEEE Transactions on Industry Applications.

[18]  Nasrudin Abd Rahim,et al.  Design and prototyping of an optimised axial-flux permanent-magnet synchronous machine , 2013 .

[19]  F. Profumo,et al.  A comparison between the axial flux and the radial flux structures for PM synchronous motors , 2001, Conference Record of the 2001 IEEE Industry Applications Conference. 36th IAS Annual Meeting (Cat. No.01CH37248).

[20]  M. Mirsalim,et al.  A Coreless Axial-Flux Permanent-Magnet Generator for Automotive Applications , 2008, IEEE Transactions on Magnetics.

[21]  Z.Q. Zhu,et al.  Minimization of Cogging Torque in Axial-Flux Permanent-Magnet Machines: Design Concepts , 2007, IEEE Transactions on Magnetics.

[22]  Matteo Felice Iacchetti,et al.  Axial Flux PM Machines With Concentrated Armature Windings: Design Analysis and Test Validation of Wind Energy Generators , 2011, IEEE Transactions on Industrial Electronics.

[23]  M. D. McCulloch,et al.  Axial flux permanent magnet machines: A new topology for high performance applications , 2006 .

[24]  R. Wallace,et al.  Cogging torque reduction in an axial flux PM machine with extended speed range , 2005, IEEE International Conference on Electric Machines and Drives, 2005..

[25]  D. Howe,et al.  Analytical prediction of the cogging torque in radial-field permanent magnet brushless motors , 1992 .