Variable tuning in LCL compensated contactless power transfer pickups

This paper analyses the effects of tuning deviation in the resonant tank of an LCL Inductive Power Transfer (IPT) pickup. It also proposes a method of active tuning which maintains unity power factor at the input to the pickup. By varying the second inductor in the LCL network, variations in the tuning capacitor can be compensated which also acts to increase the output power to the load after the retuning action. The power increase is limited by the available control action and component rating. A self tuning pickup has been built using a saturable inductor to vary the impedance of the tuning components. The pickup successfully maintains unity input power factor when the tuning was deliberately deviated.