Harmonics?

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Saywatt

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I've been asked to bypass the 400w metal halide ballasts in over 100 high-bay fixtures in a large warehouse, and install 200w mogul base florescent bulbs. The voltage is 277.

Should I be concerned about the increased harmonics?
 
What is a mogule base flourescent lamp?

Roger
 
It shouldn't be any more of a concern than the MH fixtures were and in reality probably less.

Roger
 
roger said:
It shouldn't be any more of a concern than the MH fixtures were and in reality probably less.

Roger
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Especially if it's an old MH fixture. Newer electronic balasts like those in CLFs and their ilk are using better power supplies (assuming you don't use cheap Chinese junk) that are designed to reduce harmonics.
 
Jraef said:
Especially if it's an old MH fixture. Newer electronic balasts like those in CLFs and their ilk are using better power supplies (assuming you don't use cheap Chinese junk) that are designed to reduce harmonics.
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OP said the voltage is 277.
I know flourscent tubes do not care but the ballast does.
Does the ballast in a CFL care about voltage?
 
Jraef said:
Especially if it's an old MH fixture. Newer electronic balasts like those in CLFs and their ilk are using better power supplies
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The input for a electronic ballast is a rectifier which results in non-linear current.
Conventional ballasts usually use linear components don't they?
 
Besoeker said:
It's interesting but not really comparing apples with apples.
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This is true. What I was trying to point out was that a practical to way to address the problem may be to research the availability and specify ballasts with low THD. I was not suggesting that harmonics are going to be an issue as a matter of fact, just that the issue may exist.
 
skeshesh said:
They can. Here's a brief read: http://www.geappliances.com/email/lighting/specifier/downloads/Total_Harmonic_Distortion.pdf
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TBH, I think it is sales speak rather than of any technical value.
You can't simply take 23% THD and say that it has any meaningful relationship to power. But that's what the author has done. The 23% THD in current adds 23% to the total power? That's just nonsense. Apart from anything else, harmonic currents are at multiples of fundamental supply frequency. You can't treat them in the same way.

Take a simple example. Imagine your THD has just a second harmonic component and that it's zero crossover is at the same time as the fundamental. In the first half cycle of the fundamental, the second harmonic will have made a full cycle - half positive and half negative while the fundamental voltage is all positive. The power at the harmonic frequency is net zero.

I also have a bit of a problem with the contention that a magnetic ballast takes non-linear current. And quite a lot of it. Maybe the wound components operate into the saturation mode. I don't know.

And this statement:
"However, solid-state electronic devices have been shown to be the largest contributor to distortion due to the switching of diode bridges producing a discontinuous current, which then causes a distorted sine wave."
from someone promoting electronic ballasts seems like a bit of an own goal.
 
Besoeker, I don't disagree with your statements. I only stated that they could be a problem and posted a point of view that claims they are and proposes a simple solution.
Almost all in our business have a bias and I only assume the OP can easily determine the bias in that article based on the source.
I never claimed that I believe there will certainly, or even likely, be a problem with this installation. However, if the budget allows and it would help people sleep better at night though, there are plenty of ballasts with low THD and they are not much more expensive than regular ballasts.
 
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