Wireless power supply technology has a rapid development trend in these two years, but the most widely used one is the one-way charging inductive charging technology. However, there have been reports recently that a Japanese university has developed a new technology that can provide two-way wireless power supply.
Saitama University in Japan produced a two-way wireless power supply system for pure electric vehicles (EV). In addition to being able to supply power to the EV via the charger, this system can also be powered backward from the EV and used for applications such as V2H (Vehicle to Home) and V2G (Vehicle to Grid) for power dispatch between EVs and homes.
The team that developed the system is a research team composed of Professor Abemao and others from Saitama University’s Institute of Technology. Abe et al. previously developed a power supply unit using square coils for non-contact charging of EVs. The goal is to use a capacitor in series with the power supply side (primary side) coils and a parallel connection of the capacitors of the power receiving side (secondary side) coils. Secondary shunt capacitor method (series-parallel connection method, SP method). The SP method is characterized in that if the coil turns ratio is selected as the reciprocal of the coupling coefficient, the voltages on the primary side and the secondary side can be made equal. With this feature, bidirectional power supply can be achieved by further improving the circuit configuration. In general, if the inverter is provided on the secondary side for the reverse power supply, the shunt capacitor will have problems. The research team of Abe et al. solved the problem by adding a reactor to the secondary circuit and fine-tuning the capacitance of the series capacitor of the primary coil to achieve bidirectional power supply.
Abe et al.'s research team introduced the trial results of the two-way non-contact power supply system at the Japan National Conference of the Electric Society held in Hiroshima at the end of March 2012. But at the time, the distance between the primary and secondary sides was only 70mm. The trial production system has proved through experiments that even if the distance between the primary side and the secondary side is extended to about 160 mm, which is about 2 times the original, the efficiency will not be significantly reduced. Professor Abe said, "We think 160mm is a practical distance." According to reports, the power supply efficiency between the primary and secondary coils is approximately 93% in one direction and approximately 93% in the reverse direction. In addition, the power for this experiment was 3 kW and the frequency used was 50 kHz. Abe et al. are scheduled to present details of this experiment at the Institute of Electrical Studies held in February 2013.
The system developed by Abe et al. of Saitama University adopts a square coil, which has a greater tolerance for lateral position shift during charging than a circular coil, and is therefore attracting attention from automobile manufacturers and others. Halo IPT, which is also engaged in the power supply system business for EVs, is also developing square coils. According to reports, Abe et al. began publishing research papers on square coils from around 2007 and also applied for related patents. In the future, they intend to work with companies to jointly promote the use of square coil and SP power supply systems.
Spring Steel Wire,Steel Wire,Binding Wire
Galvanized Steel Wire Co., Ltd. , http://www.nswiremesh.com