Analytical modeling of a multi-coil system for inductive powering of movable low-power wireless devices

Inductive power transfer provides interesting possibilities for supplying movable devices. In this paper, an analysis of the inductive link for a multi coil system consisting of an array of air-core transmitter coils connected in series is carried out. An analytic model for the system is proposed and the corresponding equations are solved numerically. These equations are verified then by simulation. The good fitting between analytic and simulation results implies the validity of the proposed model. The theoretical analysis is first highlighted to extract the critical parameters in order to achieve a large powering range and relative good efficiency. For the same reason, a series-series resonant tank is considered for both sending and receiving sides. A method to improve both link and power efficiencies is also proposed by setting an optimal load at the receiving side. The investigation shows that the system is capable to send 239milliwatts over 30 mm coil to coil distance and reaching 71.42% coil to coil efficiency and 14% as total efficiency.