Design and Validation of an Unconventional 39-Slot PM Synchronous Motor With Asymmetric and Unbalanced AC Windings

AYDIN M., Demir Y., Yolacan E., GÜLEÇ M., El-Refaie A. M.

IEEE JOURNAL OF EMERGING AND SELECTED TOPICS IN POWER ELECTRONICS, vol.10, no.2, pp.1733-1744, 2022 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 10 Issue: 2
  • Publication Date: 2022
  • Doi Number: 10.1109/jestpe.2021.3078092
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Compendex, INSPEC
  • Page Numbers: pp.1733-1744
  • Keywords: Windings, Torque, Stator windings, Forging, Rotors, Permanent magnet motors, Power capacitors, Asymmetric winding, cogging torque, permanent magnet (PM), synchronous motor, torque ripple, winding design, MAGNET BRUSHLESS MACHINES, COGGING TORQUE, OPTIMIZATION, NUMBER, SLOTS
  • Kocaeli University Affiliated: Yes


One of the main issues in manufacturing rotors for integer slot surface-mounted permanent magnet (PM) synchronous motors is the rotor skew. Motor manufacturers typically prefer to avoid skewing due to the added complexity and the difficulty in controlling the accuracy of the skewing and achieving the required outcome. This article proposes a design that minimizes torque ripple without using any kind of skewing in the rotor using asymmetric ac windings with unconventional stator slot-pole combinations. First, feasible slot and pole combinations are reviewed for PM synchronous motors. Theory behind unconventional asymmetric and unbalanced ac winding PM motors is presented. A lumped-parameter magnetic equivalent circuit for such unconventional stator is provided for a 1.7-kW PM motor. Detailed 2-D finite element analysis (FEA) is performed and compared with the lumped parameter model. A prototype motor is manufactured, and open-circuit as well as full-load tests are performed. Good agreement between the analytical, FEA, and test results is obtained.