Magnetic design considerations to improve nonlinear characteristics of inductively coupled power transfer systems

Purpose - This study seeks to apply finite element analysis to study the proximity effect in a multi-pickup inductively coupled power transfer system, quantify the effect and propose improved pick-up configurations. Design/methodology/approach - A mixture of approximate analytical formulae and accurate finite-element simulations has been used as a tool for qualitative and quantitative analysis. Simplified consideration of magnetic flux paths aids understanding, whereas detailed numerical computation provides reliable performance prediction. Findings - It is shown that a multi-pickup formation of conventional E-pickups may lead to power loss due to negative coupling between neighbouring pickups and that the phenomenon is nonlinear. Thus, two novel configurations for multi-pickup systems have been proposed, an alternately-directed Z-pickup and a spilt-type E-pickup, both showing improved linearity, increased total power and more efficient use of ferromagnetic material. Research limitations/implications - The investigation aimed mainly at the electromagnetic performance, while economic issues will still need to be addressed. Practical implications - The proposed pick-up configurations may be very helpful in systems where improved performance is needed but space or configuration limitations restrict or eliminate the possibility of using other designs. Originality/value - The finite-element aided magnetic field simulation has proved invaluable in achieving difficult design objectives. The combination of a simplified analytical approach and detailed numerical analysis has provided a reliable tool for accomplishing improved designs.