Wireless charging system for electric vehciles

Showa Aircraft Industry Co Ltd have developed a contactless power supply system that is an electromagnetic induction type and can supply power even when two coils are placed adjacent to or 1m apart from each other.

The company exhibited it at AT International 2009, a trade show that is taking place from July 15 to 17, 2009, at Pacifico Yokohama in Yokohama City, Japan.

In an electromagnetic induction method, electric power is transferred between the primary and secondary coils. It can supply power from a distance of about 10cm but has some problems such as displacement in a horizontal direction and heat generation due to an invasion of a foreign substance.

Showa Aircraft Industry did not disclose the details because of patent-related issues. But the new system can have a transmission efficiency of 90% or more between coils that are set about 60cm apart from each other, the company said.

The system uses almost the same frequency as before but does not employ a resonance method. However, the transmission efficiency of the entire system including the power source is less than 50% because the system still uses, for example, a power supply device for laboratory use, Showa Aircraft Industry said.

The company had a demonstration of lighting ten 100W incandescent lamps using coils that are 60cm apart from each other. In addition, when a metal frying pan was placed between the coils, it did not heat up. The size of the coils was 50 x 50cm, and the thickness was about 5cm.

Showa Aircraft Industry expects that the new system will be used for supplying electric power to trucks, whose floors are difficult to be lowered. There is a demand to supply power to the auxiliaries of refrigerated trucks by using an external power source when they are parked at convenience stores, etc, the company said.

The technology could also be used to recharge electric cars, perhaps even when paused at traffic lights or parked in car-parks, without the healthy & safety or security hazard of a physical connection.

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