無線給電は電気自動車の充電などへの応用が期待されるが、漏洩磁界が周囲と干渉するため、大電力を送る場合には重い磁性材料を用いたシールドを要する。そこで本研究では磁性材料を用いない漏洩磁界の抑制に向けて、片面に偏った磁界分布を示すHalbach配列に着想を得た共振器構造を提案する。さらに数値最適化手法による設計を行い、従来手法と同等の電力効率を示しつつ漏洩磁界が84%減少する共振器構造を実現した。

Wireless power transfer can empower various electronic systems such as EVs. However, as leakage magnetic fields interact with ambient objects, shielding methods using heavy ferromagnetic material are usually necessary for transferring large power. We present a ferrite-less resonator with an asymmetric magnetic field pattern focused on one side of the resonator, which can suppress the leakage field. To overcome the challenge of achieving an asymmetric field pattern, we developed a wiring pattern that generates a magnetic field pattern analogous to Halbach arrays and further showed that optimized structures can simultaneously achieve field suppression and efficient power transfer. Numerical analyses and simulations show that the optimized coil structure can reduce the leakage magnetic fields by 84%, observed 15 cm downward from the top of the transmitter, which will allow higher level power transfer within field exposure limits.

Yuichi Honjo, Takuya Sasatani, Cedric Caremel, Yoshihiro Kawahara

Contact: honjo@akg.t.u-tokyo.ac.jp