Companies around the world are working to develop magnetless electric motors to make them a more viable option for electric vehicles. ZF Friedrichshafen followed the same path of wireless inductive communication as German automotive supplier Mahle, but with a unique configuration. ZF saves space by integrating its inductive converter into the rotor itself, creating a compact, magnetless motor that dominates today’s electric vehicles.

By replacing the magnets in the rotor of the motor with electrical windings, manufacturers can eliminate the costs, environmental damage and potential supply chain disruptions associated with the extraction of rare earth materials required for these magnets. However, conventional magnetless designs include additional physical elements such as slip rings or brushes necessary to pass electrical current to the rotor windings, increasing the size and weight while increasing friction and the potential for wear. This is why EV manufacturers tend to choose the path of least resistance, relying on permanent magnet motors.

Contactless induction is a promising solution that eliminates its shortcomings by sending electricity to the rotor coils without physical brushes or rings.

To further this work, ZF integrates the inductive transducer into the rotor shaft in the middle of the coils, eliminating the additional 3.5 inches (90 mm) of axial space estimated to be occupied by physical solutions such as brushes, while delivering power and torque density. Torque comparable to PSM.

ZF calls this design the Inductive Inductive Excitation Synchronous Motor (I2SM), and the idea is that an automaker could replace the PSM with this new type of motor without sacrificing anything in terms of packaging or performance. ZF also claims that in continuous operation at high speeds such as highway traffic, the I2SM will operate more efficiently than the PSM.

The ZF induction converter looks more compact than alternatives like Mahle, which uses two larger diameter discs around the outer circumference of the rotor shaft. Of course, it is not possible to definitively compare these two prototype systems or conclude that the ZF is “the world’s least compact and dense electronic engine without magnets and rare earth elements”.

For now, ZF has announced plans to continue production development to integrate I2SM units into 400V and 800V electric drive platforms for supply to passenger car and commercial vehicle manufacturers. Source