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A friend of mine is having a large, fancy / artistic lamp at home (Europe) and uses a "500W incandescent bulbs on 230V" as recommended by the manufacturer (link).

His problem : every month or so the bulb blows up, and he needs to change it (it's annoying and these bulbs are expensive). It mostly (only?) blows up when he turns on the light from the wall electrical switch (which actions the wall socket where the lamp is plugged into).

Without being certain, I suspect the issue is coming from overvoltage (*).

My question : if indeed the cause is overvoltage, what would be a simple (in a minimalistic sense), yet practical and robust electrical / electronic circuit that a hobbyist could build to insert between the mains socket and the lamp plug to remove the surge? I assume that the right combination of inductors, capacitors, resistors or diodes (maybe a fuse?) used properly could be enough, but if more "fancy" components could make a significant improvement (eg gas discharge tubes?), then why not.

Thanks for your help.

(*) not very scientific but in order to make sure that the issue is not due to a defective wall socket (or another part of is home's electrical wiring), I suggested that he temporarily plug the lamp into another socket, in another room. He did that but he got the same issue (burnt two bulbs in 3 months). I am not living nearby, so I could not go and test the surge myself.

PS : for those of us who are "environmentally minded", I did suggest to stop using incandescent bulbs, but he would not listen - apparently the point with these lamps is to use old style bulbs, that's what makes their charm (I do not really understand but anyway my motivation is elsewhere, I want to learn how to fix this sort of technical issues efficiently).

Addition : here are a couple of photos of the bulbs used, in case it helps.
enter image description here enter image description here

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    \$\begingroup\$ "inrush current limiter" \$\endgroup\$ Mar 17, 2015 at 15:22
  • \$\begingroup\$ Do measure the voltage too. Incandescent light bulb lifetime is quite sensitive to voltage, and a country with nominal 230 might go up to 240 and still be in spec. \$\endgroup\$
    – tomnexus
    Mar 17, 2015 at 17:01
  • \$\begingroup\$ years ago there was an item about the size and look of a copper penny that you put in at the base of the light bulb and the bulbs would last much longer ! I haven't seen them in over 30 years . Don't know if anyone else has any knowledge of these ? \$\endgroup\$
    – user137137
    Jan 26, 2017 at 21:40
  • \$\begingroup\$ There were two kinds, The Bulb Saver and the Bul Miser. Bulb Savers were a diode, so the lamp would get 1/2 wave AC (pulsating DC?) and put out a smaller amount of light, but last a lot longer. The Bulb Miser was an NTC thermistor, so it started out as high resistance and the resistance would drop as it heated up. The Bulb Miser was therefore specifically targeted at the inrush issue of cold tungsten filaments. \$\endgroup\$
    – JRaef
    Jan 26, 2017 at 22:35
  • \$\begingroup\$ Sadly, Bulb Miser went out of business a few years ago. Bulb Savers (the diodes) are still theoretically available on Amazon.com, but the only remaining seller now wants $99 for a package of 3, so most likely they are no longer made either and he wants to capture desperate buyers. There is a website for hacking your own Bulb Miser alternative however. understandwebsites.com/bulb-miser-alternatives.html \$\endgroup\$
    – JRaef
    Jan 26, 2017 at 22:36

2 Answers 2

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The surge is called inrush current, the cold filament has a much lower resistance than the hot filament.

This is why bulbs usually fail as they're turned on.

The simplest solution might be to fit a regular light dimmer, and turn them up slowly. Or a suitably rated Negative Temperature Coefficient device could be used as an inrush current suppressor.

try this search for a lot or articles and manufacturers.

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Incandescent photoflood bulbs run the filament really hot, so their life is very short- typically only about 50-100 hours average. If he's using that kind of bulb the only way to lengthen the life significantly is to reduce the voltage (or use a different bulb). There's a bit of a myth that inrush is what reduces the life- it typically doesn't reduce the life by much but the bulb that's on the edge with a worn-out fragile, brittle and notched filament tends to fail when it is turned on and thermally shocked- but it was going to fail anyway pretty soon.

I suspect if he puts a typical low-cost triac-based dimmer on there he'll have a really annoying 100Hz pinging from the filament mechanical resonances. There may be more expensive dimmers that minimize that effect- check your local market.

Another option would be to make a box that knocks down the voltage a bit. A 240:24V transformer (100VA should be plenty) could extend the life considerably if wired in buck configuration (or shorten the life considerably if wired to boost). Of course the light output and colo(u)r temperature will both drop.

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  • \$\begingroup\$ I think he might be using the low temperature "hipster lightbulbs" which are large, yellow, long filament, old looking bulbs. Very expensive to buy and to run, but you can't put a price on it... \$\endgroup\$
    – tomnexus
    Mar 17, 2015 at 16:57
  • \$\begingroup\$ @tomnexus Hard to imagine a 500W one of those- they're usually something like 40W, and they run the filaments so cool that they should last a very long time (the electricity costs per lumen are quite unfavorable, of course). One of my local Starbucks had them for about a year until they swapped them out for fake ones made with arrays of of neon-orange LEDs inside a glass envelope. \$\endgroup\$ Mar 17, 2015 at 17:10
  • \$\begingroup\$ @ Spehro true, 500 W is too much. They do look quite low power. Ok, must be bigger bulbs, more like a stage lamp or halogen floodlight. \$\endgroup\$
    – tomnexus
    Mar 17, 2015 at 17:16
  • \$\begingroup\$ Some projector bulbs (e.g. Bell & Howell DJL) have a low-temperature filament in series with a high-temperature filament to reduce in-rush current. I don't think the makers would have bothered if in-rush current weren't a problem (the low-temperature filament is outside the reflector and contributes no useful light to the projected image). \$\endgroup\$
    – supercat
    Feb 2, 2016 at 0:05

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