Equivalent circuit of interleaved air-core toroidal transformer derived from analogy with coupled transmission lines

Abstract

An air-core transformer is a suitable device for megahertz-class power converters. This letter presents an equivalent circuit of a fabricated interleaved air-core toroidal transformer. In order to determine the modeling parameter of the transformer, the electrical characteristics are discussed on the basis of the frequency responses measured from 0.1 to 110MHz. As a result, it is found that the fabricated transformer is dominated by the mutual capacitance in addition to the self- and mutual inductance. The proposed equivalent circuit is distributed parameter model. This is derived from analogy with the coupled transmission lines. The equivalent circuit shows an excellent agreement with the experiment. These results conclude that the importance of the mutual capacitance to be implemented as a distributed parameter.