Vitesco Technologies will present some innovations in the field of vehicle electrification at the 35th International Electric Vehicle Symposium (EVS) from June 11-15 in Oslo. Among them is a separately excited synchronous electric machine that is said to be optimized for long-distance electric vehicles.
Unlike permanently excited synchronous motors (PSM) that are widespread today, externally excited synchronous machines (EESM) do not require any rare earths. The reason is simple: unlike PSM, a permanent magnet with rare earth (therefore permanently excited) is not installed in the rotor, but a coil. The EESM is not based on a permanent magnetic field of a permanent magnet, which is actuated by the magnetic field generated in the stator, but magnetic fields are generated by coils in both the stator and the rotor.
As Vitesco states, EESM (often referred to as Synchronous Excited Current Machines or SSM) is more efficient than PSM, especially at higher speeds. According to the supplier, it is especially suitable for long distances with fast driving on the highway. What Vitesco does not explicitly state in the connection: because the magnetic field of the turn can also be turned off, EESMs have similarly low pull losses as asynchronous motors (ASM). This makes them more suitable for electric all-wheel drives than for PSMs, where the permanent magnetic field causes losses – which must be compensated for by either a mechanical clutch or a complex zero torque control.
Only: Vitesco has not yet provided technical data on the planned EESM (at least in the announcement). However, it is clear that the supplier is already planning: a portfolio expansion is being prepared “which will make EESM technology available for an already successful hub motor including power electronics”.
By the way, Vitesco sees not only the advantages of EESM: the fifth generation of electronic drives from BMW (for example in the iX3, i4, iX, i7 and iX1) are also externally excited synchronous motors.
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