Mode-based semi-analytical model to characterize the coupling from large machines to test wires

Checking if the radiated emission of large machinery complies with the fundamental requirements of the European Directive on ElectroMagnetic Compatibility 2004/108/EC is a big challenge as the current, standardized measurement procedures are complex, expensive, and very often even not possible. Based on the results obtained within the framework of the TEMCA2 project, a number of alternative measurement methods have been proposed. A test wire (or microstrip) is positioned close to the machine and the induced voltages/currents are measured. So far, little or no theoretical models are available to get physical insight in the coupling from the large machinery to the test set-up or to study the influence of e.g. the exact location or loading of the test wire. In this paper, a semi-analytical method based on the equivalence and Lorentz reciprocity theorem is proposed, allowing to quantify the coupling from large machines to the TEM mode of the test wire (or microstrip).