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KAIST Wi-Power system transfers energy over a 5m range

Posted: 21 Apr 2014 ?? ?Print Version ?Bookmark and Share

Keywords:wireless power? KAIST? dipole coil? resonance system?

A team of researchers at KAIST notched up a milestone in wireless power transfer with a distance of up to five metres between transmitter and receiver coils.

Led by Chun T. Rim, a professor of Nuclear & Quantum Engineering at KAIST, the researchers developed a "Dipole Coil Resonant System" (DCRS). The system has a maximum output power of 209W at 20kHz, and can charge 40 smartphones simultaneously even if the power source is five metres away.

DCRS prototype

Figure 1: A prototype of the DCRS turns a LED television on at a 5-metre distance.

The system is based on MIT's Coupled Magnetic Resonance System (CMRS), introduced in 2007, which used a magnetic field to transfer energy for a distance of 2.1m. However, the CMRS has fallen short of extending the distance of wireless power due to technical limitations including: a rather complicated coil structure (composed of four coils for input, transmission, reception, and load); bulky-size resonant coils; high frequency (in a range of 10MHz) requirement to resonate the transmitter and receiver coils, which results in low transfer efficiency; and a high Q factor of 2,000 that makes the resonant coils very sensitive to surroundings such as temperature, humidity, and human proximity.

Rim worked out these design problems, giving the DCRS an optimally designed coil structure that has two magnetic dipole coilsa primary one to induce a magnetic field and a secondary to receive electric power. Unlike the large and thick loop-shaped air coils built in CMRS, the KAIST research team used compact ferrite core rods with windings at their centres. The high frequency AC current of the primary winding generates a magnetic field, and then the linkage magnetic flux induces the voltage at the secondary winding.

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