Toroidal Nanocrystalline Powder Core With Trapezoidal Cross Section

Abstract

This paper introduces a toroidal nanocrystalline powder core with a trapezoidal cross section. The non-uniform magnetic flux distribution of toroidal cores with different cross sectional geometries is discussed, the inductance equations are derived, and the geometrical optimisation factor is given in order to retain the highest possible inductance value whilst minimising material usage. A 10-turn coil is wound on the core, with the measured inductance values showing a good match with both FEM and mathematical calculation. The near-field electromagnetic interference (EMI) radiation in close proximity to the inductor is investigated by both FEM and experimental validation, and the toroidal core with a trapezoidal cross section has shown reduced EMI. By adopting a trapezoidal cross section for the toroidal core, a 30 % reduction in material usage and lower EMI are achieved, albeit with a compromise of 14% in inductance.