About a week ago, I had posted a link to an article in Electronic Design News which talked about the poor quality of the current crop of Compact Fluorescent Lamps.
Because these lamps do not draw power uniformly, they can present a lot larger load to the power company than is listed on their rated specification. An 18 Watt bulb might actually be drawing 26 Watts. This doesn't show up on your bill as most residential power meters do not measure the power factor.
Reader Man Mountain Molehill took the time to actually run some numbers and it's bad. Here are two images that show what is happening:
Scale factors: Voltage is 50V/div, Current is 200mA/div.
RMS line voltage is 126V, RMS current is 220MA.
Blue = V, Green = I
This works out to almost 28 watts worth of heating effect in the source for only a nominal 15 watts worth of light. No wonder the power companies are worried.
There are good technologies for power factor corrected switching supplies available, but they add a lot of cost, and never caught on, even though many governments here and in Europe tried to mandate high PF, low harmonic loads.
The truncated voltage wave is what things look like these days, since a huge percentage of the load takes current at or near the peaks.
And this is what the current harmonics look like out to 2kHz. Just awful.The dirty dark secret of CFLs. Costco is starting to sell LED lights -- no bulb lights yet, just two kinds of flood and a small candelabra base lamp. I will look forward to replacing the CFLs as they die out with these...
Completely Wrong. Yes they do create Harmonic distortion but in order for it to be a problem the amount of non linear loads must exceed 1/3rd of the buildings transformer size........200 AMPS Transformer == 66 AMPS or CFL, UPS, Clock Radios.
The only devices that have a linear power draw are inductive motors, heater elements, incandescent light bulbs to name a few. And No LED lightbulbs will not fix this. They also draw power in a non linear form as they are purely a diode.