Study of misalignment for On Road Charging

A major problem concerning On Road Charging of Electric Vehicles via Inductive Power Transfer (IPT) links is the large variation in power transfer and efficiency due to displacement of the secondary from the primary. This paper looks into this problem referred to as misalignment, both laterally and longitudinally. For lateral misalignment, experimental results were obtained by considering horizontal and vertical coils separately. The technique of combining the quadrature coils to form the quadrature pickup so as to obtain a flatter mutual inductance profile is suggested by directly combining the individual secondary coils. Longitudinal misalignment is particularly of interest when sectional primaries are to be constructed. In case of longitudinal misalignment, unsymmetrical mutual inductance profile at the extremes of the primary was observed experimentally. The concept of “Edge Effect” was introduced to explain the same. A solution to this problem is suggested and the concept of Best Efficiency Point (BEP) introduced. Theoretical efficiencies were obtained to select the best configuration of the primary for power transfer.