A New Transformer Model with Separate Common-Mode and Differential-Mode Capacitance

Abstract

A new transformer equivalent circuit model is presented containing separate common-mode and differentialmode capacitors, allowing for direct and simple analysis of the transformers influence. The representation of common-mode and differential-mode signals in two-winding transformers have been described and presented. Problems related to two commonly used transformer equivalent circuit models are shown. Operation scenarios of an isolated full bridge phase-shift DC/DC converter is used to compare the new transformer model with a commonly used model. Three transformers with different turns-ratio are constructed, with the purpose of evaluating the transformer models. Both models provided accurate impedance prediction for transformers with turns-ratio equal to one. However, for turns-ratios different from one, the commonly used model has an error of 40%-132% in the predicted equivalent capacitance of the measurements, whereas the proposed model only has an error of 0.6%-7.3%. The proposed model is therefore the only model that predicts accurate transformer behavior for any turns-ratio.

Parasitic Capacitive Couplings in Medium Voltage Power Electronic Systems: An Overview

“…According to the definitions of capacitive couplings in Sec. II the terminal-to-terminal couplings can be considered as parallel capacitive couplings and the winding-to-winding couplings are the series capacitive couplings which in the literature are also sometimes considered as CM capacitive couplings [205]- [207].…”

Calculation of Planar Transformer Capacitance Based on the Applied Terminal Voltages

“…Many different equivalent circuit models exist in the literature which represent the parasitic capacitance of a transformer [11], [12]. A simple three capacitor model that clearly separate the influence of the respective lumped capacitors, is the symmetrical transformer model [13], [14]. The symmetrical transformer model is shown on Fig.…”

“…10b. The plot shows that the stored energy is concentrated at turns corresponding to places where large voltage differences are predicted when using Table III along with equations ( 12) and (13).…”