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Subject - harmonics
JJ wolf I'm an electrician out of missouri and I just recently completed the wiring of an animal hospital. Actually an addition, anyway after the job was done we noticed a humming sound coming from the lights and from the breakers on the lighting circuits. I first thought it might have been a harmonics problem so I provided a larger service ground and drove another ground rod, but the humming was still thier although weakened. I was just wondering if anybody has came across a problem like this one. The transformer on the pole was upgraded when the addition was added could there be something screwy in the windings
JimmyDee I'm wondering if the noise is being generated from the newer style electronic ballasts. Don't have a solution but I would think that there should be some type of filter for this situation. It is my understanding that these ballest chop part of the sign wave off for its solution to limit current but I'm not sure. Enough of that going on at the same time would cause the noise. ???
Jim
JJ wolf Yes they are electronic ballast thats why I was thinking it could be a harmonics or an unbalanced problem.
JimmyDee
quote:

• Our electronic ballast use state-of-the-art printed circuit boards along with U.S. and Japanese components. Electronic ballast use 25% less energy than magnetics, do not hum or flicker when starting, and have a lower THD.
What is THD?
• THD stands for Total Harmonic Distortion. The distortion is feedback caused by deviation from the sinusoidal waveform. The industry standard is less than 20%. If the THD is very high (around 150%), an electrical fire can occur. Magnetic ballast run 90%-120% THD.

This is the results of an hour of research on Google. I think it answers your question as to harmonics. They do produce hamonics but it appears as though not as much as regular ballest. I found it interesting that these ballest opperate at around 20 kHz and that is why you don't get any flicker from the lights.
From http://www.ace-ballast.com/faq.html.
Jim
Ryan_J How would changing the grounding electrode system address a non-linear harmonic load problem?