The ubiquitous increase in the use of mains power switching devices has been paralleled by the increase in nuisance tripping of GFCIs and other protection devices. Nuisance tripping can be identified to contain such high frequency signals and these must be properly taken into account when designing proper GFCI operation in this environment.
Inductive loads and interrupted currents are an explosive combination. High voltages, arcing, and HF broadband noise are some typical effects. The phenomena behind these transients is complex, but it is not difficult to understand the fundamentals and how to minimize the effects.
“I’ve all ready read the books on EMC and visited a lot of home pages... But all these references did not mention anything about the physical phenomenon that causes common mode currents... Are common mode emissions inherent in any physical system? Can I model them?” Overheard on the ‘Net
It’s by no means a trivial question. And, in spite of decades of hand waving by authors and consultants, the principal mechanism by which common mode currents are created in digital devices was not well understood until the decade of the 90s. In this article, we’ll explore the physics behind the creation of common mode currents, and perform some experiments to verify our understanding.