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One of its Kind EV Drivetrain Exhibited in Vienna

A new rotor without permanent magnets is now part of the platform development.

by Aishwarya Saxena

Vitesco Technologies has demonstrated its latest innovations of its EV drivetrain without permanent magnets for more efficient electric driving at the 44th Vienna Motor Symposium.

VitescoAs a result of Life Cycle Engineering, the fourth generation of its fully integrated electric axle drive platform (EMR4, Electronics Motor Reducer) is being broadened by a new option to enable an even better life cycle assessment.

A new rotor without permanent magnets is now part of the platform development.

This rotor forms the core of an externally excited synchronous machine (EESM), which works without rare earth materials.

This reduces the rotor costs, and it avoids the carbon footprint that comes with mining and processing the ores.

“Top results in the sustainability and efficiency of electric cars will be achieved, if the vehicle drive is optimally adjusted to the specific scenario. The externally excited rotor without permanent magnets is a particularly sustainable option for our customers. The higher the performance requirements to the drive, the more economically attractive EESM technology becomes,” said Thomas Stierle, division head of Vitesco Technologies’ Electrification Solutions.

Up to now, most electrified cars have synchronous machines with permanent magnets in the rotor (so-called PSMs, permanent magnet synchronous motors). They are efficient and were generally regarded as easier to manufacture than externally excited machines, which use coils in the rotor to generate the magnetic field.

“Obviously, the EESM option requires an additional inverter module to control the coils,” said Gerd Rosel, head of innovation in the Vitesco Technologies division Electrification Solutions.

“Nevertheless, we are really close to an EESM plug-and-play solution.”

In addition to saving the cost for permanent magnets and the improved sustainability, this type of machine offers further advantages.

“When the vehicle is sailing efficiently, the externally excited machine saves a watt-hour of electricity per kilometre because there is no drag from a permanent magnet field in the rotor,” Rosel added, “this lowers the power requirement of the drive by up to five percent without the need for a mechanic decoupling device.”

Vitesco Technologies has overcome some substantial obstacles to designing externally excited machines.

By harnessing many years of experience from series applications and through targeted design changes, it became possible to achieve the same performance class with both technologies (PSM and EESM) – and to use the existing space in the platform design for both options.

By applying a sophisticated winding principle, the innovative EESM rotor becomes an economically attractive option within the most recent drive platform.

Especially, when high-performance requirements necessitate a big magnet mass in a PSM, EESM machines will be more affordable and more sustainable.

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