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

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.