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Very Important Development: Motor needs no Rare Earths

Slashdot posted an article about a new motor under development in Germany. Here's a partial description:

-------------------------------------------------------------------------- Magnets, typically using rare earth metals like neodymium, are found at the heart of most electric vehicle motors. It's nice to have a permanent source of powerful rare earth magnetism in your rotor, because using powered coils instead means you have to somehow transfer electricity from the battery through to the coils in a spinning rotor. That means you'll need a sliding point of contact, and sliding points of contact develop wear and tear over time.

Mahle's highly efficient new electric motor ditches rare earth metals altogether, instead using contactless induction to feed power to coils in the rotor.

Rather than magnets, the rotor uses wound coils.

A wireless transmitter sends power to the rotor, using an alternating field that's converted into direct current for the magnet coils.

The ability to continuously tune the magnetism of the coils in the rotor has enabled Mahle to make this a super-efficient electric motor across all operating speeds, particularly excelling at high speeds.

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This is significant. Neodymium is not used, and the new motor promises to be cheaper and more efficient. It also has unintended consequences.

Neodymium has an abundance of about 41.5 ppm. But in mining it, you also get about 8.1 ppm of thorium:

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So in needing less neodymium, you will also get less thorium. This is significant since thorium is used in liquid flouride thorium reactors, (LFTR), which is the new energy source for the planet. This will be a concern in the future, when we run out of material we have on hand, and the new motor means not as much will be mined.

This could be a problem after the mining companies have gone out of business when the new motor hits the market. So just when LFTR starts taking off, the fuel becomes scarce.

Reply to
Steve Wilson
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Don't you think they will mine for the Thorium alone? Seems to me it would be worth a lot more as fuel than the rare earths are or will have been.

Reply to
Rick C

The description of the motor makes me wonder if it is just a model of the ubiquitous shaded-pole AC motor.

Reply to
Tauno Voipio

There are lots of motors and generators around that have wound rotors and couple to the rotor through magnetic fields. Big AC generators do this, with rotating transformers and bridge rectifiers to excite the rotating field. Synchros often couple to the rotor through a rotating transformer along the shaft, to avoid brushes.

This doesn't sound terribly original.

Magnets are a pretty efficient way to make a magnetic field.

Reply to
jlarkin

The same argument was raised in the slashdot discussion. Apparently Mahle is doing it a significantly different way that results in higher performance. You'll have to read the slashdot link to understand it.

Reply to
Steve Wilson

Wasn't there a diagram that showed RF stimulation?

Reply to
Rick C

There has been a lot of press, and investment, in EVs lately. And a lot of press about rare earth shortages. This screams investment opportunity.

Someone else just reinvented the variable reluctance motor. And laminated steel pole pieces. The press releases emphasize how they use STEEL instead of rare earths.

Reply to
jlarkin

On Friday, 14 May 2021 at 08:18:40 UTC-7, snipped-for-privacy@highlandsniptechnology.com wrote: ...

.. The Tesla Roadster and Model S/X cars used induction motors from day one, in 2009, no rare earths; just iron and copper.

They recently changed one of the two motors to use permanent magnets as they have a bit higher efficiency at low powers. The other is still an induction motor. Tesla did pioneer the use of the Halbach array to reduce the amount of rare earth magnetic material needed in the permanent magnet motors.

Even in the permanent motor designs used by Tesla, BMW and others they are designed such that about 30% of the torque is derived from the variable reluctance so minimizing the amount of rare earths, although it is difficult to do larger amounts and get acceptable noise and torque ripple. Some mild-hybrid cars do use wound rotor variable reluctance motors for low cost.

kw

Reply to
ke...

So far so good but you do have to wonder what they do use to concentrate the magnetic field to a useful level.

We used to make two sorts of mass spectrometer: Soft iron cored ones that could beam switch at a leisurely pace consistent with slow very precise measurements and air cored ones that used a lot more power but could really thrash things around quickly for surveys.

I don't see how they could get the field strength needed to make this work effectively unless they have found a magic form of soft iron core.

Reply to
Martin Brown

On Friday, 14 May 2021 at 10:31:24 UTC-7, Martin Brown wrote: ...

Not sure what you mean by "work effectively".

Most electric vehicle permanent magnet motors have the magnets embedded within conventional silicon steel and a wound stator also using conventional silicon-steel laminations. These are generally known as Interior Permanent Magnet motors. They obtain some 30% of their torque from variable reluctance with the remainder from the permanent magnets.

This development from Mahle seems to be just a modern brushless exciter adapter for electric vehicles. Such exciters for large alternators have been around since the 1950's, it is difficult to see what is new about this design.

kw

Reply to
ke...

Yeah, but every induction motor has 'winding' elements in the rotor (and a shorted winding works well, for AC drive systems).

The trick is, to get the right field geometry, a PERMANENT magnet can be permanently damaged, while a magnetized core can be designed to shape the field and will never age out of spec.

Iron rotors are mechanically better than exotic magnets. The "new" design just uses a bunch of stuff to avoid slip rings (and slip rings are plenty good, IMHO). A smart electric car can tell you when to replace the wear parts, so I'm not seeing this innovation's appeal.

Reply to
whit3rd

Yes, I agree on slip rings. Hundeds of millions of cars have alternators that use slip rings. They often last longer than the car.

Reply to
Steve Wilson

Motorcycles are usually PM alternators and some are used in cars. I did a crash self-education course in PM alternators and started with one from a Deere rider lawn motor.

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The real thing is used to power a jet-engine FADEC.

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Here's the result:

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It's hard to simulate a PM alternator because, as speed increases, the open-circuit voltage gets huge and it approaches a constant-current source. The regulators typically short them to regulate.

Reply to
John Larkin

I took it to be like a brushless alternator but run in reverse.

Reply to
Jasen Betts

it doesn't sound original.

magnetic fields don't take a lot of power to maintain, and using a variable field is a long established way to get efficient speed control in traction motors without varying the supply voltage.

using a variable field in an electronically commutated rotating field motor does seem original though

Reply to
Jasen Betts

I'd be surprised if they managed to patent it.

Reply to
Bill Sloman

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