Rapid Chargers for Electric Cars Could Become Faster and Cheaper With New Concept
In a promising step towards everyday electric cars, researchers at Chalmers University of Technology have developed a unique integrated motor drive and battery charger that is much faster and cheaper at the same time. Compared to today's chargers, they claim to have managed to shorten the charging time from eight to two hours, and to reduce the cost by around $2,000.
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Saeid Haghbin, doctor of electric power engineering, said he undertook his doctoral studies in order to attempt developing the optimal electric vehicle charger. "The ideal scenario would be to have a charger powerful enough to charge a car in five to ten minutes, but this would cost over $100,000, which is more expensive than the car itself," says Saeid Haghbin. "The question we posed was: how can we reduce the size, weight and price of the on-board charger."
This resulted in a novel high-power integrated motor drive and battery charger for vehicle applications, where a new power transfer method has been introduced involving what is known as a rotating transformer. Since the electric motor and the inverter are not used during battery charging, the researchers looked into the possibility of using them in the charger circuit and building some kind of integrated motor and battery charger and thus increasing the charging power at a lower cost.
"Instead of having a separate isolated battery charger, we introduced a new concept for the power transfer, the rotating transformer, which was developed to transfer electric power while rotating," says Saeid Haghbin. "The battery is charged through the transformer and a split-phase electric motor that was especially designed for this purpose."
The Chalmers integrated charger is, from a university perspective, still on laboratory level and requires a great deal of further investigations and experimentation. However, the product has resulted in both a Swedish and an international patent already. Chalmers is trying to find a potential industrial user, and Volvo AB is working on the concept for further enhancement to be used in its system.