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Improved Electric Vehicle Charging, Research at Chalmers University of Technology

Chalmers' Rotating Transformer Could Revolutionize Electric Vehicle Charging
Chalmers’ Rotating Transformer Could Revolutionize Electric Vehicle Charging

Electric vehicle opponents love to cite, and some owners have to admit, that electric vehicles are limited by range and recharging capabilities.

Even industry-leading Tesla Model S 85kWh is limited, in best case scenario, to about 300 miles and still needs access to one of just eight Superchargers to refuel in nearly an hour [30 minutes for a half-charge]. A comparably-equipped Lexus ES300h, on the other hand, has a range of 688mi and refuels in less than five minutes at any of 100,000 gas stations.

Improvements in electric vehicle battery and charging technology will help many to see the benefit of making the switch to electric. Researchers at the Chalmers University of Technology in Sweden have been looking into how the charger can be made smaller, more efficient, and less expensive. The charger they’re looking at isn’t the one mounted on the ground, but the one mounted in the vehicle. The ultimate goal of such a project would be to make an onboard electric vehicle charger that’s comparable to refueling an electric vehicle.

The solution they came up with is to remove the charger altogether and change the electric motor. Since the electric motor isn’t in use while recharging, and the onboard charger isn’t in use while driving, it only seems logical to combine the two into one unit, which saves weight and money. Think about it: the electric motor also functions as a generator when regenerative braking, so why not use the electric motor for charging when the vehicle is stationary?

If I understand the thesis correctly, [I do not have a PhD] the new electric motor uses all of the windings while driving, both for traction and for regenerative braking. During charging, the motor is decoupled from the drivetrain. Part of the windings are powered by an external charging station, and the rest of the windings function as a generator to charge the battery, just like during regenerative braking.

Now, Saeid Haghbin’s design calls for a clutch to separate the motor/charger from the rest of the drivetrain for charging, which leads me to believe that the motor turns due to the application of external power to just one pair of windings. His design is called a rotating transformer, which leads me to believe that Haghbin’s design generates power for the battery more efficiently and more powerfully due to the combination of electrical induction and rotating motion. The technology is still in laboratory stage, but could revolutionize electric vehicle charging if it is reliable and cheap enough.

Image©Chalmers University of Technology

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