Basics

“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.

In this article, a time-domain EMI measurement system for the frequency range from 10 Hz to 40 GHz is presented. Signals with a frequency of up to 1.1 GHz are sampled by an ultra-fast floating-point analog-to-digital-converter (ADC) and processed in real-time on a field-programmable-gatearray (FPGA). An ultra-broadband multi-stage down-converter allows for the measurement of signals with frequencies up to 40 GHz. Measurement times can be reduced by several orders of magnitude compared to traditional EMI-receivers that work in frequency-domain.

As the wireless receiver sensitivity levels surpass thermal noise levels, reliable operation of smart grid Distributed Generating System (DGS) wireless communication and control devices demands consideration of the power line produced noise spectrum. The power line noise spectrum varies based on voltage and current of transmission lines and load characteristics. The electrical-noise environment is anticipated to be more severe in a DGS than in a Conventional Electrical Power System (CEPS) due to the frequent changes in power distribution routing.

The lack of conversation around the environment, climate change, and our energy economy during the 2012 election season, while widely noted, still seemed to attract little attention. Certainly health, financial and national security issues were more immediate concern for many voters. Yet, the lack of initiative at the federal level has not kept technical innovators, astute business people and local governments from moving forward with new ideas for addressing our environmental and energy concerns.

Editor’s Note: Over the past months we’ve explored one engineer’s view of historical patterns and events that have set the landscape for today’s economic challenges. In this final installment, Mr. Kervill brings us into the present and concludes the series by summarizing his predictions for the future. Communication is so fast that it is not a factor in restricting today’s technology. Not only is the world flat, as described by Thomas Friedman, but it has only one time zone.