Differentiating coupling factor and VA transfer of IPT systems using bipolar pad primaries

Abstract

Coupling factor is a important design parameter in inductive power transfer (IPT) systems as it determines the amount of VA effort required from the primary pad to deliver the necessary VA to the secondary pad. As IPT systems involve more complex magnetic systems such as multi-coil primary pads (whose currents can have an amplitude and phase difference), the effective coupling factor becomes more difficult to describe and validate. Typically, an equivalent T-model is used for two coupled single coil pads; however, this is insufficient for multi-coil primaries such as a bi-polar pad (BPP). As such, this paper introduces an equation which is able to describe the effective coupling factor of an IPT system with a multi-coil primary and a single coil secondary while considering the reflected impedances between the coils.