Harmonics Help
Harmonics Help
(OP)
I have a question concerning harmonics. We have a 240v single phase lighting panel that is feeding some 400w metal halide high bay lighting fixtures. The main CB is 100A and the branch circuits are 20A. When all of the lights are turned on the main breaker is seeing about 50 amps. Each of the branch circuits are only seeing about 10amps. The branch circuit conductors are all on the same conduit for about 10feet before they branch out from a junction box. However, they have been derated appropriatley and are 10guage. From day one when this panel was installed, the circuit breakers seemed to be unusually warm. The conductors are fine, but even the main breaker is warm. An infrared temp gun shows temps of 150 defF on the breakers, in 70 deg ambient temperature. Being that heat seems to be transferring from the brakers themselves, and the currents are by no means excceding any of the ratings, it must be harmonics generated by the all inductive load of the ballasts. This wasn't a cheap panel. I used a Seimens bolt-in type panel. I am wondering what I did wrong, and how do I prevent this in the future. Also, if someone could give me a simplified harmonics explanation, it would be nice.






RE: Harmonics Help
If you use a clamp and it is a TRMS clamp, then the thermal effects from the harmonics should be evident from the measurement.
If you calculate current instead of measuring it, the harmonics will add to thermal load and the effect will be exactly what you see. Your lamps do probably have a spec saying what the power factor (not displacement, but total power factor, sometimes denoted with greek letter 'lambda') is. Use that power factor when you calculate breaker and panel load.
There is so much written about harmonics on the web that you can find all information you need. But avoid the 'popular and simplified' explanations that involve ropes, boats, trains, beer froth and whatever people come to think of. Just think of harmonics the way they occur IRL, as deformed waveforms with peaks that are higher than needed and thus causing more heat than needed because heat is proportional to current squared. Twice the current is half the time does the same work, but heats conductor and breakers twice as much. Simple as that.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Harmonics Help
RE: Harmonics Help
Does your Fluke also show crest factor? If it is very high, then it is possible that the fluke saturates and shows too little current. Have you tried to measure with the next higher range?
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Harmonics Help
RE: Harmonics Help
RE: Harmonics Help
RE: Harmonics Help
RE: Harmonics Help
Like marks1080, I question whether harmonics are really the problem.
What is the normal temperature of the thermal element of a thermal-magnetic breaker with 50% load? I'm not convinced that there is even a problem.
RE: Harmonics Help
RE: Harmonics Help