Simple Method for Estimation of Stray Capacitance of Toroidal Inductors by Considering an Insulation between Winding and Core

Abstract

In this study, the authors propose a simple method for estimating stray capacitance of toroidal inductors. The proposed method calculates the total stray capacitance of a toroidal inductor based on the stray capacitance between the winding and the core, calculated by considering the insulation (plastic case and plastic molding) that contains the magnetic core. The frequency characteristics of the toroidal inductor can be calculated by substituting the calculated stray capacitance in the analytical model of the inductor, which takes into account the frequency dependence of the complex magnetic permeability of the magnetic material. In order to evaluate the proposed method, toroidal inductors were fabricated based on carbonyl iron dust, amorphous and nanocrystalline magnetic cores. Comparison between measured and calculated impedances clarify that the proposed method can calculate the stray capacitance of toroidal inductors with practical accuracy.