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Author Topic: Does it waste power to leave a burnt out CFL in the socket?  (Read 1717 times)

Offline CliffordK

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A couple of years ago I replaced many of my lightbulbs with CFL bulbs.  Since then a few have burnt out, and if they didn't seem to be lighting a vital part of the room, I've left them out. 

If a classic tungsten filament bulb burns out, then the circuit is broken and no power is lost.

But, what about CFL bulbs with all the electronic circuitry inside?  Or fluorescent tube lights?

Actually, I just replaced a couple of my fluorescent tube lights with LEDs, and discovered that one of them might have been working with a 100% short...  which puzzles me a bit.


 

Offline syhprum

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I can only guess at the electronics within a CFL lamp base but would expect it to be a half bridge rectifier fed via a capacitor feeding a chopper chip.
there would probably be another capacitor directly across the input terminals to reduce radio interference.
This capacitor could have gone short circuit or the feed capacitor could have shorted and burnt the rectifier down to a very low resistance.
If the tube had failed the power consumption would be very low
 

Online evan_au

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On old-style fluorescent tubes, the starter initiates a short circuit through an inductor, then (when it is working properly) goes open-circuit, triggering a voltage spike which ionises the gas in the fluorescent tube.
If the starter is "stuck" in the short-circuit condition, the inductor will limit the current to a safe level - but I would expect it to get hot.

The Compact fluorescent lamp has a much more complex electronic circuit, with far more failure modes, some of which may draw a lot of current. However, due to their smaller mass, they would get very hot, very quickly.

Safety standards require that the circuit will fail in a "safe" manner, eg by burning out some fuse element in series with the lamp or the ballast inductor, before it gets hot enough to start a fire.
 

Offline CliffordK

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Thanks Evan,

I went ahead and pulled out one of the burnt out CFLs, and the bulb/base was cool, indicating no substantial power consumption.  Perhaps I'll try an ammeter shortly.
 

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