From The Milken Institute Review, May 13:
Technology writers love breakthroughs. But technologies often don’t cooperate, advancing by steps rather than leaps. So it goes with electric motors.
Electric motors are, in fact, a very old technology. Benjamin Franklin experimented with a precursor, the electrostatic motor, in the 1740s, and Michael Faraday demonstrated the first electromagnetic motor in 1821. Industrial versions appeared about 10 years later, operating on direct current as supplied by batteries. Nikola Tesla invented the induction motor, which gave birth to alternating current motors, in 1874. A century and a half of incremental improvements followed.
Spruced up over the decades, the Tesla induction motor was good enough for most industrial applications and household appliances. But the rebirth of the electric vehicles a dozen years ago jumpstarted a new phase in motor development. And while media attention has rightly focused on the need for cheaper batteries that can store more energy in smaller packages, happily electric motors have been quietly improving in power output, weight and heat. These gains will contribute to a new generation of EVs with better performance, lower cost — and even green cred.
Lighter, Faster, Cheaper?Five years ago, Spectrum, the journal of the Institute of Electrical and Electronics Engineers, ran an article headlined, “Shut Up About the Batteries: The Key to a Better Electric Car Is a Lighter Motor.” Interviewed recently, the author, Prof. Martin Doppelbauer of the Karlsruhe Institute of Technology said that he didn’t write the headline, and would have chosen less provocative words, but he’s not backing down.Common industrial electric motors were already pretty efficient, turning about 80 percent of the energy they consume into power and torque, compared with as little as 30 percent for internal combustion engines in vehicles. But the motors being developed today spin ten times faster and weigh a tenth to one-hundredth as much, allowing them to achieve 95 percent efficiency. And engineers have 99 percent in their sights.
Doppelbauer and his students have eked out additional gains by combining multiple design principles in a single motor. Most EV motors use permanent magnets, which are affixed to the spinning rotor; the stationary housing, or stator, contains the coils through which electricity flows. This setup is quite efficient when the rotor is turning relatively slowly. But a few companies, notably BMW and Renault, use motors with the electric coils in the rotor, which work better at high speeds. The Karlsruhe motor finesses the trade-off by using both.
Add a few more bells and whistles and the result is a motor able to produce almost 6 percent more torque and attain 2 percent higher peak efficiency. On the road, this translates into an extra 4.4 percent driving range on a charge. What’s more, the extra range is close to a free lunch because the advanced design uses only a few additional parts, which cost less than the battery capacity they can replace. Early examples powered one team sponsored by Ka-Racing to victory in electric car racing, and a Karlsruhe motor is currently being tested by a major German auto company. “Had you asked me 20 years ago, I would not have thought this was possible,” says Doppelbauer....
....MUCH MORE
