There are news talking about the new magnet-free motor for electrical vehicles from the manufacturer Mahle. They boast an efficiency of 96%. Links: YouTube Video about it

My question is: Is a motor like that able to do regenerative braking?

  • \$\begingroup\$ On what alternative field to magnetism does the motor work? \$\endgroup\$
    – Andy aka
    Jun 29, 2021 at 14:32
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    \$\begingroup\$ Yes, it can! If you have an induction motor and you turn it faster than the nominal speed (defined by V/Hz), it becomes a generator and produces power. \$\endgroup\$ Jun 29, 2021 at 14:42
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    \$\begingroup\$ It's important to note that "magnet free" does not mean "magnetism free"; the motor still uses magnetism, it just doesn't use permanent magnets. This makes the motor somewhat bulkier, but frequently cheaper (rare earth magnets are expensive) and can allow for some more advanced modes of control (such as a doubly-fed induction machine, useful for wind turbines for example). \$\endgroup\$
    – Hearth
    Jun 29, 2021 at 14:57
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    \$\begingroup\$ Every motor type can act as a generator, if excited correctly. This includes a Switched-Reluctance (no magnets) Machine and Squirrel-Cage inductance machines \$\endgroup\$
    – user16222
    Jun 29, 2021 at 15:04
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    \$\begingroup\$ @Hearth: Electrostatic motors are not so impractical. They they can produce plenty of torque. They are limited in speed compared to electromagnetic motors because the rotor and stator are separated by a dielectric fluid gap rather than an air gap. The resulting drag limits the speed, but they are said to be competitive in the 100 - 2000 RPM range. c-motive.com \$\endgroup\$
    – user80875
    Jun 30, 2021 at 12:59

2 Answers 2


The motor described is a wound-field synchronous motor with a brushless excitation system. It is basically the same machine as most large power station generators. Yes, it can provide regenerative braking.

The "new" aspect of this motor is said by the manufacture, Mahle Gmbh, to be the excitation system. It is a wireless system that they have designed. The motor is being developed as a vehicle traction motor with the motor and controller integrated into a single housing. It appears to be a liquid cooled assembly.


Instead of updating I am going to answer my own question here, because since people on this platform have helped me identify what I was really looking for, I have found a good source of information on a similar or maybe even identical motor design (Mahle GmbH does not disclose much, as far as I could find). So here goes my attempt to give back to the community.

For anybody else interested in this:

Here is the link to the publication:


For the less fortunate who also lack access to that journal:

This document was written by one of the authors of the paper above.

EDIT: Section 12 here talks about using the motor as a generator, therefore I would at least conclude that regenerative braking should be possible, which merely confirms the more elaborate answers of the community.

  • \$\begingroup\$ You asked "Is a motor like that able to do regenerative braking?". So your answer is...? \$\endgroup\$ Jul 1, 2021 at 4:55
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    \$\begingroup\$ I am aware of the excitation system. patented by Ludois & Hagen. It is capacitive rather than inductive. The Mahle images and statements pretty clearly indicate that they are using an inductive system. The Ludois & Hagen technology is available for license: warf.org/technologies/summary/P190295US01 – \$\endgroup\$
    – user80875
    Jul 1, 2021 at 15:06

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