131103-1124 EDT
taywoo:
You list yourself as an electrical engineer. So do some basic study.
An incandescent bulb is basicly a resistive element. However, its resistance does change with voltage or current and therefore can not be described as a constant resistance over its range of operation. The thermal time constant of the filament is sufficiently long relative to 1/120 second that there is not much change in resistance within a half cycle of 60 Hz power. At any one input voltage level it is reasonable to call the resistance constant. Also with 60 Hz power there is not much modulation of light intensity, but there is some. Any sort of voltage or current adjustment from 0 to maximum will provide light adjustment from 0 to maximum. Power factor is 1.00 .
A flourescent lamp is not a constant resistance load, but approximately a constant voltage load. Needs to be driven by an approximately constant current source. Its time constant for light output is dependent upon the characteristics of the phosophers used to convert UV to visible light. There is substantial intensity modulation with 60 Hz power. A typical current source for older fluorescent fixtures was a current limiting inductor. Electron emission from the electrodes is required for current flow, to get high current flow this means heated electrodes. Typically heating is from the current flow. Thus, a dimming problem. Dimmable fixtures supply external current to the filaments in the bulbs to get good dimming range, and dimming is controlled by current adjustment. Power factor is not 1.
Fluorescent electronic ballasts use high frequency current, 20 to 100 kHz, to drive the bulb. To get this excitation the 60 Hz power is converted to DC, and an oscillator and current limiting mechanism drive the bulb. Numerous problems exist relative to adjusting the output current from some change in the input 60 Hz power.
CFLs use high frequency current, and AC to DC to oscillator. To get much dimming range something has to be done to interpret the input 60 Hz signal. Package size limitations prevent good dimming control. On one type of standard CFL I got better dimming range with adjustable sine wave voltage (a Variac) than a phase shift dimmer with a so called dimmable CFL. On the other hand the dimmable CFL had moderately constant light output with variable sine wave input from about 100 to 130 V.
A Cree LED I have tested has fairly good dimming range with either Variac or phase shift average voltage adjustment, but not comparable to incandescent. The phase shift dimmer was a three wire device. I believe most screw-in LED replacements for incandescents convert AC to DC.
Two wire phase shift dimmers require a suitable load to supply power to the internal electronics to perform control of the Triac switching element. A three wire dimmer can provide electronic control of the Triac with or without a load. Power for the electronic circuit is provided from hot to neutral. Thus, the firing angle of the Triac is unaffected by the load. There may be some problems with reactive loads because the Triac turns off at a current zero crossing.
Start with a three wire dimmer and one of your LED bulbs and see how it performs. If it is poor, then get a $10 to $13 Cree from Home Depot and try it. Use a scope to look at your waveforms.
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