Structure of Bundled Windings and Copper Loss for Core-less Power Inductor

In this paper, we propose a high frequency power inductor for an automatic matching unit of a plasma generator. For the power inductor, the change in the inductance with respect to frequency, temperature, and current value must be prevented as much as possible. Moreover, it is required to have low loss, small size, light weight and low cost. In the conventional research, the inductance and the loss per unit weight were evaluated in terms of coil shape, bundle shape of winding and laminated structure; then, their effectiveness was confirmed. However, the methods for dividing the flux and loss generation mechanism caused by the proximity effect have not been investigated. Therefore, the purpose of this paper is to clarify these points and to derive a structure showing high characteristics. The proposed structure is a flat wise type coil with wide window area. A rectangular wire with thickness equal to or less than the skin depth is used as the winding wire. Furthermore, the experimental results suggested the practical effectiveness of the proposed structure.