Beyond induction motors — Technology trends to move up efficiency

Premium (IEC IE3 Class) efficiency Motors are now mandatory in North America. Super-Premium (IEC IE4 Class) and IE5 Ultra-Premium efficiency classes are defined in the second edition of Standard IEC 60034-30. For line-start fixed-speed applications, Super-Premium IE4-Class Line-Start Permanent-Magnet Motors and Squirrel-Cage Induction Motors are recent entrances in the industrial motor market. For variable-speed applications, IE4-Class Variable-Reluctance Synchronous Motors are also a recent entrance in the market. For the low power range, moving from IE4 to IE5 class, may require moving away from radial-flux induction motor technology, into to the permanent magnet and reluctance technology, either using Rare-Earth or Ferrite magnets. In this paper, efficiency analysis on the best available electric motors and emerging motor technologies, such as axial-flux permanent-magnet synchronous motors, is presented. The potential efficiency gain associated with several design options as well as a study on the theoretical efficiency limit achievable taking into account those existing design options are described.