Influence of shielding materials on coil characteristics in inductive wireless power systems

Inductive wireless power systems rely on a low frequency, non-radiating, alternating magnetic field that may interfere with nearby objects or devices. In order to prevent this interference, the coils of inductive wireless power systems are often equipped with a shield consisting of ferrite or a combination of a ferrite and a metal plate. However, these materials have a significant influence on coil characteristics such as self inductance, equivalent series resistance, parasitic capacitance, quality factor and self resonance frequency. This paper discusses the influence of the mentioned shields on a wirewound pancake coil. The observed effects are discussed and their influence on the performance of a wireless power system is evaluated. These results can consequently be considered in the magnetic and electrical design process of a wireless power system.