A Simple Method to Build a Linear Circuit Model for a Multiwinding Transformer Used in EMI/EMC Analysis

This letter presents an easy-to-use technique for identifying lumped parameters of equivalent circuits for multiwinding transformers. The equivalent circuit helps to model electromagnetic-compatibility (EMC) noise. This letter takes two paths to create linear models for a multiwinding transformer: 1) RLC with physical meaning of all components, but limited to 10 MHz and 2) a nine-port S-parameter black-box model, but valid up to at least 1 GHz. The method is illustrated on a single-core transformer with four windings used in a flyback converter for an automotive 40–1000-V input auxiliary power supply for an 800-V battery system.