Contactless Power Supply System Claims 95% Efficiency at 40cm Range

Aug 20, 2009
Keisuke Ogawa, Nikkei Automotive Technology
The sending and receiving units placed in parallel
The sending and receiving units placed in parallel
[Click to enlarge image]
The sending and receiving units placed in directions perpendicular to each other
The sending and receiving units placed in directions perpendicular to each other
[Click to enlarge image]

Nagano Japan Radio Co Ltd developed a contactless power supply system for electric vehicles and mobile phones.

The distance between the sending and receiving units can be several tens of centimeters to 1m. When the transmission distance is 40cm, the transmission efficiency is 95%. The company plans to expand the application of the system by improving the output from the current several tens of watts to several kilowatts.

Contactless power supply systems have already been used for electronic devices. However, their transmission ranges are short, and their sending and receiving units have to be precisely positioned.

The newly developed system consists of power sending and receiving coils, a power controller for the sending unit and so forth. It can efficiently transmit electric power even when the central axis of the receiving coil is misaligned from that of the sending coil by several tens of centimeters or the two coils are placed in directions perpendicular to each other. It is because the sending unit automatically detects the displacement of the central axis and the orientations of the coils.

There are two methods for contactless power supply, the electromagnetic induction method and the magnetic resonance method. This time, Nagano Japan Radio employed the latter method. However, with the magnetic resonance method, the transmission efficiency drastically lowers when the positions of the sending and receiving units are displaced only by several centimeters. This time, the company increased the degree of freedom in layout.