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Home > Issues > SearchMutual Inductance Analysis of Rectangular Spiral Coils with Angle and Position Variations for Wireless Power Transfer
Journal of Magnetics, Volume 25, Number 1, 31 Mar 2020, Pages 92-100
Juwan Kim (Dept. of Electronic and Comm. Eng., Konkuk University, Seoul 05029, Republic of Korea), Wei Huang (Transcom Instrument Co. Ltd, Shanghai, China), Jae Woo Chung (Dept. of Information Comm, Materials and Chemistry Convergence Tech., Soongsil University, Seoul 06978, Republic of Korea), Hyunchul Ku * 
(Dept. of Electronic and Comm. Eng., Konkuk University, Seoul 05029, Republic of Korea)
(Dept. of Electronic and Comm. Eng., Konkuk University, Seoul 05029, Republic of Korea)
Abstract
For wireless charging, a misalignment between a receiver (Rx) coil in the devices (EV, drone and IMD) and a
transmitter (Tx) coil often occurs. In this case, a mutual inductance between the coils changes, and consequently
a power transfer efficiency (PTE) of the wireless power transfer (WPT) system also changes. To analyze
the WPT system in such a situation, this paper presents an analytical method using Neumann formula to
derive mutual inductance considering angular and position variations of two rectangular spiral coils. To verify
the proposed method, magnetic resonant WPT systems of 85 kHz and 6.78 MHz are implemented, and the PTE
values derived from the analyzed mutual inductance and the measured S-parameters are compared for the
cases of angle and position variations. For each case, the two PTE values agree well with each other, and it is
verified using the normalized root mean square error (NRMSE) values.
transmitter (Tx) coil often occurs. In this case, a mutual inductance between the coils changes, and consequently
a power transfer efficiency (PTE) of the wireless power transfer (WPT) system also changes. To analyze
the WPT system in such a situation, this paper presents an analytical method using Neumann formula to
derive mutual inductance considering angular and position variations of two rectangular spiral coils. To verify
the proposed method, magnetic resonant WPT systems of 85 kHz and 6.78 MHz are implemented, and the PTE
values derived from the analyzed mutual inductance and the measured S-parameters are compared for the
cases of angle and position variations. For each case, the two PTE values agree well with each other, and it is
verified using the normalized root mean square error (NRMSE) values.
Keywords: Wireless Power Transfer (WPT); mutual inductance; neumann formula
DOI: https://doi.org/10.4283/JMAG.2020.25.1.092
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