Circuit Modelling for Electromagnetic Compatibility



Modelling the Transient Emission from a Twin Conductor Cable


Plain language title
Estimating the level of electromagnetic interference caused by transient currents


What’s it about?

Using the equations of transmission line theory, a program is developed to simulate the response of an open-circuit line to a step pulse. This is compared with the observed response of a twin conductor cable. It is deduced that not all of the current delivered to the send conductor arrives back via the return conductor. Some of it departs in the form of radiated emission.

A virtual capacitor is used to simulate this, with limited success. However, by adding a second virtual capacitor to simulate transient current being delivered from the return conductor back to the send conductor, a fair correlation is achieved between theoretical and actual results. This analysis demonstrates that the return conductor plays an active role in propagating any signal along the cable.

Why is it important?

This paper demonstrates that a circuit model can be created to simulate the mechanisms involved in the radiation of interference from power supply cables. The analysis can be carried out by any electrical engineer since it relies solely on the techniques of Circuit Theory.



This is but one example of the use of circuit models to analyse electromagnetic interference.

Visit IET Library to download paper.