Wireless power transfer has many promising applications, such as contactless powering, electric vehicles, and energy harvesting. To construct a wireless power transfer system, a “wireless transfer coupler” is necessary to deliver the energy from a high-frequency power source to a load, with no physical contact.
In the past, “coupling coefficient k” was used as an index of wireless-power-transfer efficiency. Since k decreased as the power-transfer distance increased, it was believed that the transmission efficiency would decline. In 2007, however, it was found that the transfer potential could increase, even over large distances, if the Q factor (quality factor) was high.
“A function to simultaneously estimate and display the ?max (maximum efficiency, see Reference 3) of a wireless transfer link from the kQ product using tan ? (the efficiency tangent) has also been realized,” explains Professor Ohira. “Using this newly developed measurement system, it is possible to greatly improve prototypes and design high-efficiency couplers for wireless power transfers.”
This system contributes to the construction of highly efficient wireless power-transfer systems by enabling the following.
- Finding the maximum transmission efficiency by changing (scanning) the power transmission and reception positions.
- Improving development speeds through the quick discovery of structures and dimensions.
- Rapidly discovering the dependency of the optimum transmission frequency on structural parameters.
This newly developed “kQ measurement system” will accelerate the realization of various wireless power-transfer applications in our everyday lives; for example, contactless powering of home applications, battery-free electric vehicles, and energy harvesting.
This system is introduced at CEATEC JAPAN 2015 (Combined Exhibition of Advanced Technologies; Japan’s largest IT and electronics exhibition), in Makuhari, Japan, October 7-10, 2015.