The minimization of magnetic stray fields from transformers with air gapped toroids

Abstract

In this paper the external magnetic stray field is investigated in transformers realized on gapped toroids with a rectangular cross section. An analytical method is used in which the field distribution is calculated by means of orthogonal expansion. Based on the results, basic rules are given that need to be followed in order to optimize transformers used in flyback and load resonant converters under EMC constraints.