Traction motor gets by without rare earths

Traction motor gets by without rare earths

Technology News |
By Christoph Hammerschmidt

At the 44th Vienna Motor Symposium, Vitesco presented a traction motor that does not require rare earths and thus has the potential to contribute to more sustainable electromobility.

Vitesco is adding an additional option to the fourth generation of its fully integrated electric axle drive platform (EMR4, Electronics Motor Reducer) in the course of life cycle engineering: as part of the platform development, a new rotor option without permanent magnets is now offered. This rotor forms the heart of an externally excited synchronous electric machine (EESM), for which rare earths are no longer required. This reduces the costs for the rotor and also eliminates the CO2 footprint for the extraction and processing of the ores.

Up to now, electric vehicles have mainly used synchronous motors with permanent magnets in the rotor (PSM). They are efficient and were previously considered easier to manufacture than externally excited machines, in whose rotor coils generate the magnetic field. Vitesco now believes it has overcome the decisive hurdle in the design of separately excited machines: By means of targeted design changes, it was possible to achieve the same performance class for both technologies (EESM and PSM) – and to use the available installation space for both options. In combination with a sophisticated winding technology, the innovative EESM rotor thus becomes an economical option for the latest drive platform. Especially when high power requirements demand large magnetic masses in the PSM, EESM machines are cheaper and more sustainable.

“Of course, the EESM option requires an additional module in the inverter to control the coils,” says Gerd Rösel, Head of Innovation in the Electrification Solutions Division at Vitesco Technologies. “Nevertheless, we are very close to an EESM plug-and-play solution.” In addition to the cost savings for permanent magnets, greater security of supply and higher sustainability, this type of machine has other advantages: “When the vehicle is rolling in an energy-saving manner, the externally excited machine saves one watt-hour of electricity per kilometre, since there is no permanent magnetic field braking the rotor,” Rösel continues, “thus reducing the power requirement of the drive by up to 5% – and that without a mechanical disconnect clutch.”

The technology presented is suitable for main and auxiliary drives; it can also open up further performance advantages, the company says.

Related articles:

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ZF starts series production of CeTrax light truck drivetrain

BMW, Continental invest in innovative electric motor technology

Nidec’s 2nd-gen EV traction motor enters mass production

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