Extremum co-energy principle for analyzing AC current distribution in parallel-connected wires of high frequency power inductors

Inductor winding is often composed as parallel-connected wires to suppress the copper loss. However, in high frequency inductors, the proximity effect can cause concentrated AC current distribution, hindering suppression of the copper loss. Therefore, optimization of the physical inductor structure requires predicting the AC current distribution. Although simulators are commonly employed for predicting the AC current distribution, simple analytical methods are also required for effective design or invention of the inductor structure with less copper loss. The purpose of this paper is to propose a novel analysis method of the AC current distribution in parallel-connected wires of high frequency inductors. The proposed method is based on a novel insight that the AC current is distributed to give an extremum of the magnetic co-energy contributed by the AC flux and the AC current under the given total AC current. Experiments are presented in this paper to verify the proposed method.