So they're saying that these babies HUM LIKE HELL, or what? WTF is an audio distortion figure doing on a light fixture?!?
-- "Human nature itself is evermore an advocate for liberty. There is also in human nature a resentment of injury, and indignation against wrong. A love of truth and a veneration of virtue. These amiable passions, are the latent spark. If the people are capable of understanding, seeing and feeling the differences between true and false, right and wrong, virtue and vice, to what better principle can the friends of mankind apply than to the sense of this difference?" --John Adams
Don't get me started. THD is a useless spec. It 's like a single number indicating impurities in ice cream. Some impurities are straw, some are bat shit.
'Even order' harmonics are much easier to put up with than 'odd order' (not related to the fundamental note) harmonics. (Please, all you musicians and psycho-acousticians keep your shirts on, I know it is an over simplification.) Even order harmonics is how we tell instruments apart, odd order is ..is.. like..Celine Dijon (without AutoTune.)
What _I_ want to know is if the phases are linear in my light fixtures. Dat's impotent!
I think I prefer a 60 cycle hum to Dijon.
-- "Human nature itself is evermore an advocate for liberty. There is also in human nature a resentment of injury, and indignation against wrong. A love of truth and a veneration of virtue. These amiable passions, are the latent spark. If the people are capable of understanding, seeing and feeling the differences between true and false, right and wrong, virtue and vice, to what better principle can the friends of mankind apply than to the sense of this difference?" --John Adams
THD is not so much about accoustics as it is about "dirty power". Low TDH ballasts are becoming much more common in industrial/commercial lighting applications (specifically those with 3 phase power)
according to ITS Intertek Testing Services (Boxborough, MA)
Power line harmonics is just one of the many power quality issues that arise with public utilities. Effectively, current harmonics represent a distortion of the normal sine wave provided by the utility. When a product such as an SCR switched load or a switching power supply distorts the current, harmonics at multiples of the power line frequency are generated. Two significant consequences arise as a result of harmonic generation. First, because of finite impedances of power lines, voltage variations are generated that other equipment on the line must tolerate. Second, when generated in a three-phase system, harmonics may cause overheating of neutral lines.
Power line harmonics are generated when a load draws a non-linear current from a sinusoidal voltage. The harmonic component is an element of a Fourier series which can be used to define any periodic waveshape. The harmonic order or number is the integral number defined by the ratio of the frequency of the harmonic to the fundamental frequency (e.g., 150 Hz is the third harmonic of 50 Hz; n = 150/50). A second harmonic is therefore two times the fundamental frequency of the supply line volt current. If the supply voltage had been generated by an ideal source (zero impedance), the current distortion would have little effect on the supply voltage sine wave. However, because a power system has a finite impedance, the current distortion caused by a nonlinear load creates a corresponding voltage distortion in the supply lines. This voltage distortion can subsequently disrupt operation of other sensitive equipment connected to the same line. Voltage distortion can also cause motors operating on the line to overheat
Major understatement. Talk about dirty power nowadays...
So, how much of this affects the generation of clean light in fluor instances, generally on 120v single phase systems?
Thanks, clare. That will certainly trump any answer I get from my request about the subject in an email to Lithonia.
-- "Human nature itself is evermore an advocate for liberty. There is also in human nature a resentment of injury, and indignation against wrong. A love of truth and a veneration of virtue. These amiable passions, are the latent spark. If the people are capable of understanding, seeing and feeling the differences between true and false, right and wrong, virtue and vice, to what better principle can the friends of mankind apply than to the sense of this difference?" --John Adams
For all you ever wanted to know about power line harmonics, go to:
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problem is also very real in single phase distribution systems (120/240). The flourescent ballasts are electronic, just like the computer power supplies referenced in the above-mentioned article.
The harmonics can be REALLY nasty. Which is why, for computers (particularly servers and high power workstations), I STRONGLY recommend DUAL CONVERSION UPS units - which totally decouple the harmonics from the power line, and vise versa.
Tanks. Will peruse. Hmm, I didn't see any single phase info the first time through.
I've had a UPS on the computer since the early '90s, after losing the best sales pitch I ever made to an instantaneous glitch which rebooted my computer on me. I vowed that it would never happen again.
Are they really causing problems in fluor fixtures? I don't recall ever having heard that before. Symptoms, besides fire?
-- "Human nature itself is evermore an advocate for liberty. There is also in human nature a resentment of injury, and indignation against wrong. A love of truth and a veneration of virtue. These amiable passions, are the latent spark. If the people are capable of understanding, seeing and feeling the differences between true and false, right and wrong, virtue and vice, to what better principle can the friends of mankind apply than to the sense of this difference?" --John Adams
Large installations get nasty-grams from the power company. That's rare at the home installation scale, but not impossible. Depending how things are coupled and designed, the (electrical) noise thrown off can affect other systems that want or assume "clean" power. And (again, usually more of an issue on large installations, or ones with load metering) you can run into being limited on how many fixtures you can hang off a circuit due to poor power factor (which goes along with high distortion) causing the fixture's VA to be far larger than its wattage - and you have to size the wiring for the VA.
In most home setups none of this matters enough to worry too much about, but I'm still fairly confident that my 0.99 power factor GE replacement ballasts really are better ballasts than the 0.5 PF ones that some of the cheap lights I've bought have. From the right source, they don't even cost much more. But trying to buy a fixture with a specific ballast is a real pain in the wallet (or information that's not provided and needs to be hunted down) much of the time.
Going back earlier in the thread, the electrical distortion has nearly nothing to do with the audible noise a fixture may make. Look for an "A" sound rating if that's your concern, and avoid the old-style magnetic ballasts.
-- "Human nature itself is evermore an advocate for liberty. There is also in human nature a resentment of injury, and indignation against wrong. A love of truth and a veneration of virtue. These amiable passions, are the latent spark. If the people are capable of understanding, seeing and feeling the differences between true and false, right and wrong, virtue and vice, to what better principle can the friends of mankind apply than to the sense of this difference?" --John Adams
Egad, with a $550-1,200 entry level, I think I'll pass. I'm glad they're not needed for residential lighting.
-- "Human nature itself is evermore an advocate for liberty. There is also in human nature a resentment of injury, and indignation against wrong. A love of truth and a veneration of virtue. These amiable passions, are the latent spark. If the people are capable of understanding, seeing and feeling the differences between true and false, right and wrong, virtue and vice, to what better principle can the friends of mankind apply than to the sense of this difference?" --John Adams
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