Mechanical Design Considerations of an 'Ironless,' High-Specific-Power Electric Machine

Yuanshan Chen, Reed Sanchez, Andy Yoon, Kiruba Sivasubramaniam Haran

Research output: Contribution to journalArticlepeer-review


This paper describes the mechanical design considerations for a 1 MW, 14 000 rpm motor which achieves a specific power of at least 13 kW/kg. This is enabled through an 'ironless,' inside out, Halbach array permanent magnet, high frequency, and airgap or slotless configuration. The 'ironless' design creates mechanical challenges because thin radial builds which reduce weight also typically reduce structural stability and vibrational damping. Structural deformation challenges include radial expansion and static bending. Vibrational issues include stator resonance mode excitation as well as rotor dynamic resonance excitation. The mechanical challenges were studied with analytical calculations and high-fidelity finite-element analysis. These analyses drove design refinements to mitigate these challenges. The rotor has then been tested to verify these analysis results.

Original languageEnglish (US)
Article number7997807
Pages (from-to)855-863
Number of pages9
JournalIEEE Transactions on Transportation Electrification
Issue number4
StatePublished - Dec 2017


  • Aircraft power systems
  • permanent magnet motors
  • rotating machine mechanical factors
  • traction motors

ASJC Scopus subject areas

  • Automotive Engineering
  • Transportation
  • Energy Engineering and Power Technology
  • Electrical and Electronic Engineering


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