Abstract
In this work, we present a novel coil structure for the design of Wireless Power Transfer (WPT) systems via magnetic resonant coupling. The new coil consists of two layers of flat polygonal windings in square, pentagonal and hexagonal shapes. The double-layer coil can be conveniently fabricated using the print circuit broad (PCB) technology. In our design, we include an angle between the two layers which can be adjusted to change the area of inter-layer overlap. This unique structure is thoroughly investigated with respect to the quality factor Q and the power transfer efficiency (PTE) using the finite element method (FEM). An equivalent circuit is derived and used to explain the properties of the angularly shifted double-layer coil theoretically. Comparative experiments are conducted from which the performance of the new coil is evaluated quantitatively. Our results have shown that an increased shift angle improves the Q-factor, and the optimal PTE is achieved when the angle reaches the maximum. When compared to the pentagonal and hexagonal coils, the square coil achieves the highest PTE due to its lowest parasitic capacitive effects. In summary, our new coil design improves the performance of WPT systems and allows a formal design procedure for optimization in a given application.
Highlights
The original concept of Wireless Power Transfer (WPT) was first pioneered by Tesla over a century ago to operate a system without cables or connectors.[1]
Since the idea of a WPT system based on strongly coupled magnetic resonance was reported in 2007, it has been found that the quality factor (Q-factor) of the coupled resonators can compensate for the coupling decay in near field.[2]
We believe that there remain rooms for improvement by adopting other structures for the double-layer Polygonal Spiral Coil (PSC)
Summary
The original concept of Wireless Power Transfer (WPT) was first pioneered by Tesla over a century ago to operate a system without cables or connectors.[1]. A novel, low-cost and implementable structure of the resonance coil is presented. Such a coil is built with double-layer spiral windings in a certain angle between the two layers. This coil can be used in either the transmitter or the receiver of a WPT system as long as they have the same resonant frequency. In comparison with the totally overlapped double-layer PSC, we found that the Q-factor and the corresponding PTE can be both improved by adopting the angular winding concept. Our results confirmed the increase in both the Q-factor and the PTE as the increase in the shift angle
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