20/21 March 2024 Augsburg

The design office for the development of electrical motors

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A comparative study of the alternatives to permanent magnet excited synchronous motors in the industrial sector:




The political situation between China and Europe is tense and at the same time Europe is maximally dependent on China for magnets and rare earths. As a results of this situation, alternatives to drives with permanent magnets are currently being developed across all industries. We, therefore, would like to provide a comparison of the current motor technologies. 


Boundary Conditions:


  • inverter-fed, self-ventilated industry motor
  • frame size 112
  • IEC stator
  • 4 kW @ 1500 min-1
  • IE 4 efficiency = 91,1 %

Motor Technologies:


  • permanent magnet excited synchronous motor (PSM)
  • asynchronous motor with aluminium and copper rotor (ASM)
  • synchronous reluctance motor (SynRM)
  • electrically excited synchronous motor (El.-ex. SM)

Calculation Results:





The KSPM (PSM) is unbeatable in terms of efficiency and available space.


The ASM reaches its limits with IE4 and has no longer any cost advantage.


The SynRM is suitable for high-efficiency requirements, but is limited in terms of applications. 


The el.-ex.SM has potential for applications with high efficiency, is shorter than the ASM but longer than the PSM. In the current case, the target efficiency was not achieved due to the low speed and would require optimization of the complete geometry.