E-core Transverse Flux Machine (ETFM)

The E-core Transverse Flux Machine (ETFM) is a new mechanical design of the Switched Reluctance Motor. The new design is patented by Aalborg University, Institute of Energy Technology in Denmark, and is developed by ePower Motors ApS, who owns the ETFM patent.

The patented ETFM motor has a power range of up to 4kW.

The “flux” (magnetism) in a traditional SR motor goes through the center of the motor, but in ePower’s ETFM motor the “flux” works in the peripheral, which makes ePower’s ETFM motor more fault tolerant, and thereby more robust compared to a normal SR motor or traditional motors on the market today.

ETFM Motor The ETFM design makes it possible to integrate a gearbox.

Key features of the ETFM:

  • Robustness – The ETFM is simple in structure and the machine is fault tolerant, due to the separated phase-windings. No windings or magnets on the rotor.
  • Starting Torque – The ETFM provides a high starting torque, up to 3-4 times nominal.
  • Low speed – Maintain full rated torque down to zero speed.
  • 4 Quadrant Operation – motor and generator in both directions.
  • Low cost – Simple construction without permanent magnets and a simple rotor construction.
  • Shape – The ETFM has a short axial length, approximately the width of the E-cores
  • Gearbox – A gearbox can be integrated in the machine without increasing the physical size.
  • Low Inertia at large diameter – The Transverse flux principle makes it possible to keep the moment of inertia low at large rotor diameter. Perfect for direct drive start/stop applications e.g. with Robotics and Fitness applications.
  • Can be controlled without cogging torque from zero speed and maximal torque. Perfect for direct drive precision applications.
  • No magnetic losses at high speed with no load (free wheel) keep high efficiency at low torque.
  • No magnets - no rare earth materials used.
  • Low maintenance costs

The “flux” works in the peripheral of the motor
Traditional SR motor The "flux" goes through the center of the motor