Reluctance circuit and optimization of a novel contactless transformer

Coupling coefficient (k) of a transformer is a key parameter affecting the efficiency of a contactless energy transmission system. Aiming to obtain higher k, smaller size and lighter weight for the contactless transformer, techniques for the improvement of core structure and coil arrangement were proposed. With the help of the magnetic field simulation results using Ansoft 2D, a new magnetic reluctance circuit was proposed for the transformer. Based on magnetic flux coupling, the magnetic flux of the proposed transformer could be divided into three parts: uncoupled, partially coupled and fully coupled. And thus the magnetic flux tube was analyzed and five steps calculation visualized the effect of the core geometry parameters on the reluctance and k. Further optimization was taken and a novel contactless transformer was fabricated for a 60 W contactless energy transmission system. The k calculated was verified with experimental measurement to be very accurate. A contactless transformer with k of 0.6 and weight of 60 g was achieved. Compared with our previous transformer having k of 0.53 and weight of 122 g, the new transformer offers about 2.5% improvement in the maximum efficiency. Soc. for Elec. Eng.