Impact of Manufacturing Tolerances on a Low-Reactance Slotless PM Synchronous Machine

Dongsu Lee, Andy Yoon, Samith Sirimanna, Sheppard Salon, Kiruba S. Haran

Research output: Contribution to journalArticlepeer-review


This paper presents the impacts of manufacturing tolerances on a 1 MW slotless permanent magnet synchronous motor used in an aircraft propulsion system. The motor was designed using multiphysics analysis of electromagnetics, mechanical structure and thermal analysis to obtain a high torque density. It has several governing characteristics, including a Halbach permanent magnet arrangement, slotless stator windings, an outer rotor, lower reactance and a high current density. Since the current density of this design is high, the existence of circulating currents should be considered for safe operation under different levels of manufacturing tolerances. In particular, the low reactance of the motor and the slotless structure greatly contribute to increase the circulating current. Therefore, this paper analyzes various factors affecting the circulating current such as eccentricity and imbalanced windings. Finally, an analytical model is used to calculate magnetic and electric loading, and non-linear finite element analysis are applied and compared to obtain the machine performance.

Original languageEnglish (US)
Article number8818322
Pages (from-to)366-374
Number of pages9
JournalIEEE Transactions on Energy Conversion
Issue number1
StatePublished - Mar 2020


  • Analytical model
  • circulating current
  • eccentricity
  • finite element analysis
  • imbalanced windings
  • manufacturing tolerances
  • slotless permanent magnet synchronous motor

ASJC Scopus subject areas

  • Energy Engineering and Power Technology
  • Electrical and Electronic Engineering


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