Magnetic Emissions Reduction by Varying Secondary Side Capacitor for Ferrite Geometry based Series-Parallel Topology Wireless Power Transfer to Vehicles

Magnetic fields in surroundings of wireless power transfer system depends upon the two coil currents, distance from the coils and space angle between the two coil fields in steady state conditions. Increase in value of the secondary capacitor leads to a phase shift between the two currents and as a result magnetic emissions are reduced. But the side effect of this phase shift is reduction in the power transfer capability of the system. This paper proposes a new design method with help of theory and simulations which shows that it is possible to reduce the magnetic emissions and transmit the same power at unity power factor at expense of higher primary current and bigger capacitors on both sides. This reduction increases with increase in the secondary capacitor till a certain maximum point and then decreases. Hence this new design method can be very useful in reducing the magnetic emissions of series-parallel topology wireless power transfer to vehicles without compromising with the power transfer capability of the system.