Slot Harmonic Impact on Rotor Losses in Fractional-Slot Permanent-Magnet Machines

Fractional-slot permanent-magnet (PM) machines have several advantages, but they suffer from the high content of space harmonics in the air-gap magnetomotive force (MMF) distribution. The MMF space harmonic amplitude and frequency depend on the particular combination of numbers of slots and poles. Such harmonics induce losses in the rotor since they are not synchronous with the rotor speed. This paper compares several kinds of machines with the same stator lamination but with different numbers of phases; three-, five-, and seven-phase PM machines are considered. Several winding configurations are compared, changing the number of poles but maintaining the same number of slots. Although in each case there is a reduction in terms of harmonic content, it is shown that rotor loss reduction is lower than expected. Some considerations about the harmonic impact are given. Although no experimental results are given, this paper refers to previous works in which rotor losses have been investigated and measured experimentally.

[1]  D. Stone,et al.  Rotor loss in permanent magnet brushless AC machines , 1999, IEEE International Electric Machines and Drives Conference. IEMDC'99. Proceedings (Cat. No.99EX272).

[2]  Barrie Mecrow,et al.  A comparative study of permanent magnet and switched reluctance motors for high-performance fault-tolerant applications , 1995 .

[3]  N. Bianchi,et al.  Design considerations on fractional-slot fault-tolerant synchronous motors , 2005, IEEE International Conference on Electric Machines and Drives, 2005..

[4]  Leila Parsa,et al.  Fault-Tolerant Control of Five-Phase Permanent-Magnet Motors With Trapezoidal Back EMF , 2011, IEEE Transactions on Industrial Electronics.

[5]  H. Toliyat,et al.  Five-phase permanent-magnet motor drives , 2005, IEEE Transactions on Industry Applications.

[6]  W. Schuisky.  Berechnung elektrischer Maschinen , 1960 .

[7]  K. Atallah,et al.  Rotor Eddy-Current Loss in Permanent-Magnet Brushless AC Machines , 2004, IEEE Transactions on Magnetics.

[8]  Henk Polinder,et al.  Eddy-current losses in the segmented surface-mounted magnets of a PM machine , 1999 .

[9]  Nicola Bianchi,et al.  Impact of the rotor yoke geometry on rotor losses in permanent magnet machines , 2010 .

[10]  M. Ubaldini,et al.  Permanent Magnet Linear Actuators with Concentrated Coils , 2003 .

[11]  Katsumi Yamazaki,et al.  Rotor-Shape Optimization of Interior-Permanent-Magnet Motors to Reduce Harmonic Iron Losses , 2010, IEEE Transactions on Industrial Electronics.

[12]  N. Bianchi,et al.  Impact of the Rotor Yoke Geometry on Rotor Losses in Permanent-Magnet Machines , 2010, IEEE Transactions on Industry Applications.

[13]  Thomas M. Jahns,et al.  Analysis of Rotor Core Eddy-Current Losses in Interior Permanent Magnet Synchronous Machines , 2008, 2008 IEEE Industry Applications Society Annual Meeting.

[14]  J. Haylock,et al.  A comparative study of permanent magnet and switched reluctance motors for high performance fault tolerant applications , 1995, IAS '95. Conference Record of the 1995 IEEE Industry Applications Conference Thirtieth IAS Annual Meeting.

[15]  R. Dhawan,et al.  Seven phase brush-less synchronous motor with reduced inverter size , 2004, Nineteenth Annual IEEE Applied Power Electronics Conference and Exposition, 2004. APEC '04..

[16]  K Yamazaki,et al.  Effect of eddy-current loss reduction by magnet segmentation in synchronous motors with concentrated windings , 2009, 2009 International Conference on Electrical Machines and Systems.

[17]  Leila Parsa,et al.  An Optimal Control Technique for Multiphase PM Machines Under Open-Circuit Faults , 2008, IEEE Transactions on Industrial Electronics.

[18]  Emil Levi,et al.  Multiphase Electric Machines for Variable-Speed Applications , 2008, IEEE Transactions on Industrial Electronics.

[19]  N. Bianchi,et al.  Design considerations for fractional-slot winding configurations of synchronous machines , 2006, IEEE Transactions on Industry Applications.

[20]  Jiabin Wang,et al.  Rotor eddy-current loss in permanent magnet brushless machines , 2004, IEEE transactions on magnetics.

[21]  S Bolognani,et al.  An Overview of Rotor Losses Determination in Three-Phase Fractional-Slot PM Machines , 2010, IEEE Transactions on Industry Applications.

[22]  B. Heller,et al.  Harmonic field effects in induction machines , 1977 .

[23]  Sang Bin Lee,et al.  Optimization of Shield Thickness of Finite Length Rotors for Eddy Current Loss Minimization , 2006, Conference Record of the 2006 IEEE Industry Applications Conference Forty-First IAS Annual Meeting.

[24]  M.R. Shah,et al.  Optimization of Shield Thickness of Finite-Length Solid Rotors for Eddy-Current Loss Minimization , 2009, IEEE Transactions on Industry Applications.

[25]  Nicola Bianchi,et al.  Index of rotor losses in three-phase fractional-slot permanent magnet machines , 2009 .

[26]  Nicola Bianchi,et al.  Rotor losses in fractional-slot three-phase and five-phase PM machines , 2010, The XIX International Conference on Electrical Machines - ICEM 2010.

[27]  Silverio Bolognani,et al.  Impact of Stator Winding of a Five-Phase Permanent-Magnet Motor on Postfault Operations , 2008, IEEE Transactions on Industrial Electronics.

[28]  N. Bianchi,et al.  Magnetic Loading of Fractional-Slot Three-Phase PM Motors With Nonoverlapped Coils , 2008, IEEE Transactions on Industry Applications.

[29]  Fernando J. T. E. Ferreira,et al.  Three phase tooth-concentrated multiple-layer fractional windings with low space harmonic content , 2010, 2010 IEEE Energy Conversion Congress and Exposition.

[30]  Nigel Schofield,et al.  Parasitic rotor losses in a brushless permanent magnet traction machine , 1997 .

[31]  M. Ubaldini,et al.  HIGH POLE NUMBER, PM SYNCHRONOUS MOTOR WITH CONCENTRATED COIL ARMATURE WINDINGS , 2006 .

[32]  H.A. Toliyat,et al.  Fault-tolerant five-phase permanent magnet motor drives , 2004, Conference Record of the 2004 IEEE Industry Applications Conference, 2004. 39th IAS Annual Meeting..