Power Loss Analysis and Comparison of Segmented and Unsegmented Energy Coupling Coils for Wireless Energy Transfer

Abstract

This paper investigated the power losses of unsegmented and segmented energy coupling coils for wireless energy transfer. Four 30-cm energy coupling coils with different winding separations, conductor cross-sectional areas, and number of turns were developed. The four coils were tested in both unsegmented and segmented configurations. The winding conduction and intrawinding dielectric losses of the coils were evaluated individually based on a well-established lumped circuit model. We found that the intrawinding dielectric loss can be as much as seven times higher than the winding conduction loss at 6.78 MHz when the unsegmented coil is tightly wound. The dielectric loss of an unsegmented coil can be reduced by increasing the winding separation or reducing the number of turns, but the power transfer capability is reduced because of the reduced magnetomotive force. Coil segmentation using resonant capacitors has recently been proposed to significantly reduce the operating voltage of a coil to a safe level in wireless energy transfer for medical implants. Here, we found that it can naturally eliminate the dielectric loss. The coil segmentation method and the power loss analysis used in this paper could be applied to the transmitting, receiving, and resonant coils in two- and four-coil energy transfer systems.

Efficient Wireless Power Transfer With Capacitively Segmented RF Coils

“…The application of segmentation capacitors to multi-turn inductors for WPT has only been performed by a limited set of authors: Monti et al [31] presented a 433 MHz WPT system with a 30 mm primary segmented resonator; as the structural optimization algorithm is not detailed and as the efficiency levels for a coil distance of 20 mm are in the range of 1 %, practical applicability is limited. Tang and McDannold [38] evaluated the beneficial effect of capacitive segmentation on large inductors (diameter greater than 10 cm), explicitly denoting the reduction of dielectric losses, but not providing a generalized modeling and optimization approach.…”

“…Equation ( 63) can be used to determine the segmentation capacitors C s,ij based on the elements of the mutual inductance matrix M. In contrast to the approaches given by [30], [31], [38], the segmentation capacitor values are not equal across the coil, but are dependent on the location and effective inductance of individual segments (also see section IV).…”

Position and Orientation Insensitive Wireless Power Transmission for EnerCage-Homecage System

“…The cage made of polycarbonate, which is the substrate for L21–L25, has a relative permittivity of ε r = 3. Therefore, for the current induced in Tx resonators, λ is 13 m. To ensure the length of each segments is less than λ/10, L21–L25 were segmented into two identical pieces to prevent phase-inversion in the current distribution along L21–L25, which causes EM field cancellation at the location of L4 [33]. …”

The Study of Cross-layer Optimization for Wireless Rechargeable Sensor Networks Implemented in Coal Mines

“…Zhong et al found a way to make a three-coil wireless energy transfer system more efficient than a two-coil one [ 3 ]. Experiments were also conducted by Tang et al to show the efficiency of wireless energy transfer between unsegmented and segmented coupling coils [ 4 ]. Li et al wrote a paper introducing the potential usage of wireless energy transfer for electrical vehicles [ 5 ].…”