Contactless charging for electric vehicles with a large air gap

An induction coupler with 100mm wide air gap is being developed for contactless charging of electric vehicles with power levels up to 3kW. This will enable convenient opportunity charging at stops and maximise battery life and mileage. A core was found to be necessary, and using an iterative method, the core design was optimised for optimum coupling was found for the 100mm air gap. High frequency operation is necessary to reduce the size of compensating capacitors and the thickness and weight of the core, but is limited by the eddy current and the switching losses. An experiment was carried out to compare measurement and software modelling results. A charging characteristic was found by simulation and a frequency control strategy is proposed.