BIG spark when plugging stuff in! - possible CFL issue

[Thruxton]

Until I finished wiring my subpanel I had my shop lights hooked up to a plug that I plugged into a temp outlet when I wanted to turn the lights on. Yeah, I know, jury-rigged, but it was the easiest and given my setup safest solution.

Anyway, what I noticed was whenever I plugged them in - 6 18W lamps in the string - there was an arc a lot larger than you would expect a 108W load to cause. There is obviously a large voltage spike on startup with these lamps, one of these days I'll hook up my o-scope to the circuit to see just how much. But my question is this- the light switches I use (3-way) are likely seeing that same arcing when the contacts make and break. Anybody else see an issue here? Not so much safety as failure rate. I think I'm going to replace these switches with higher-rated units.

 

[larry_g]

Take your ohm meter and check the resistance on the plug to the lamp string. I betting you see near zero ohms as I would think your looking at the input to a transformer (ballast). So the inrush current would be quite large for the first couple of cycles of the 60 cycle ac. Once running the inductance will limit current flow.

lg
no neat sig line

 

[mrb]

CFLs are basically a dead short for one cycle when first energized.

 

[Thruxton]

Thanks, gentlemen, confirms my suspicions.

 

[Greatbear]

The internal circuitry of a CFL has the line input meeting a set of rectifiers to change AC into DC, then a relatively large capacitor (or two) to filter/smooth the DC, then the rest of the electronics that produce the high voltage the bulb needs and to start it. It's the capacitors charging that cause the arcing. The caps are practically a dead short for a millisecond or so as they charge.