Investigation of Asymmetric and Unbalanced Winding Structures for 3-Phase Permanent Magnet Synchronous Machines

Demir Y., El-Refaie A. M., AYDIN M.

IEEE TRANSACTIONS ON ENERGY CONVERSION, vol.36, no.3, pp.1722-1732, 2021 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 36 Issue: 3
  • Publication Date: 2021
  • Doi Number: 10.1109/tec.2020.3044000
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Academic Search Premier, Aerospace Database, Applied Science & Technology Source, Business Source Elite, Business Source Premier, Communication Abstracts, Compendex, Computer & Applied Sciences, INSPEC, Metadex, Civil Engineering Abstracts
  • Page Numbers: pp.1722-1732
  • Keywords: Windings, Synchronous motors, Stator windings, Permanent magnet motors, Induction motors, Layout, Torque, Fractional-slot motor, permanent magnet machine, unbalanced winding, unbalanced winding PM motor, DESIGN CONSIDERATIONS, PM MOTORS
  • Kocaeli University Affiliated: Yes


In this study, an investigation of winding structures is performed for 3-phase unbalanced and asymmetric winding permanent magnet (PM) machines including different slot-pole combinations. There are two different cases for unbalanced winding (UBW) structure: 1) Stator slot number of the machine is divisible by three, 2) Stator slot number of the machine is not divisible by three. Only the first case is examined in this paper. The unbalanced winding layouts are created for minimum unbalance and maximum winding factor. Total magneto motive force (MMF) distributions for nine different slot-pole combinations and their harmonic contents are presented. Variation of the amount of unbalance for different slot-pole combinations is also provided in the paper. Key issues arising from the asymmetric and unbalanced windings such as degree of asymmetric and unbalanced magnetic pull are explored. A prototype motor with 39-slots and 12-poles has been manufactured for experimental verification. A comparison between the finite element analysis (FEA) results and experimental results is presented for the prototype motor for both no-load and on-load conditions. It is shown that the asymmetric and unbalanced winding PM motors have significant potential for applications requiring smooth torque operation.