Tier One automotive supplier Mahle has developed an electric motor for EVs that uses no permanent magnets. It is not the first to do so, but it is the first to create a motor that is scalable to fit the needs of many sizes of vehicles, from subcompact cars to medium duty trucks. Mahle says the ability to tune and change the parameters of the rotor’s magnetism instead of being stuck with what a permanent magnet offers has allowed its engineers to achieve efficiencies above 95% right through the range of operating speeds. Only the motors used in Formula E cars offer such efficiency, according to New Atlas.
The Mahle motor is also particularly efficient at high speeds, which could help extend the range of electric cars during highway driving. “Our magnet-free motor can certainly be described as a breakthrough, because it provides several advantages that have not yet been combined in a product of this type,” says Dr. Martin Berger, Mahle’s vice president of corporate research and advanced engineering. “As a result, we can offer our customers a product with outstanding efficiency at a comparatively low cost.”
Magnet-free motors are not unheard of, but most of them require some sort of rotating contact device to send electricity to the copper coils in the rotor. That raises the possibility of more wear and tear inside the motor than a comparable motor that uses permanent magnets would encounter.
But Mahle’s engineers have borrowed ideas from the world of wireless charging to solve the contact issue. Power is transferred to the rotor wirelessly through induction by a coil carrying alternating current. That induces a current in the receiving electrode inside the rotor, which energizes the copper windings that replace the permanent magnets and creates an electromagnetic field.
As a result, there’s practically nothing to wear out, says IEEE Spectrum. “There are no contacts to transmit electricity, no abrasion, no dust formation, no mechanical wear,” Berger, said Wednesday during an online press conference. “Also I have to say, if one must service a non-magnetized rotor, it’s not difficult to exchange the rotor.” He adds that the new motor combines the best points of several motor designs by offering good efficiency at both low and high torque.
It isn’t ideal for ultracompact vehicles such as e-bikes or large trucks that generally operate at a constant load, Berger says. “Very fast or heavy vehicles would need a transmission, but for the majority of application cases — passenger cars for example — one gear is enough.”
The Rare Earth Dilemma
Most electric motors use permanent magnets made from rare earth minerals like neodymium, dysprosium, or yttrium. Actually, rare earth minerals are not all that rare. The issue is that China controls 97% of the world’s supply. Even those that are mined elsewhere must be processed in China, which is the only country with the ability to make them commercially usable. Recently, China instituted export controls that raised the price of neodymium by 750% and neodymium by 2000%. It’s not that the price of copper hasn’t increased as well as the EV revolution moves forward, but it is nowhere near as expensive as those rare earth minerals, which means the Mahle motor should cost less to manufacture.
Because of the economic and geopolitical consequences of being dependent on China for rare earth minerals, several companies, including BMW, Audi, and Renault, are making some of their electric motors without permanent magnets already. Every other EV company has its eye on new technology as well. Mahle hasn’t said which companies are interested in its new motor but says samples have already been delivered to several companies for testing and evaluation purposes. It expects to begin mass production of the magnet-free motors by the end of 2023.
Is the new Mahle motor earth-shattering news? No, but it is an example of the tiny improvements that are making the transition to electric vehicles happen faster than we might have dared hope just a few years ago. The internal combustion engine took 100 years to achieve the power, efficiency, and durability it has today.
The pace of change in electric drivetrains is much, much faster at the beginning of the electric vehicle era. By the end of this decade, expect EVs to be as far along in their development as gasoline and diesel powered vehicles were after 70 years of improvements. Change is never fast enough for some and too fast for others, but nothing can stop it from happening.