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Mercury vapor running on incandescent ballast on 120V...!

Mercury vapor running on incandescent ballast on 120V...!

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Last night I did something which I've been told is pretty much impossible - I got one of my 40/50 watt mercury vapor lamps to strike using an incandescent lamp as the ballast. Mind you, it wasn't entirely successful.

I first tried a 75 watt incandescent lamp, but the mercury vapor lamp only ran up to 65 volts, running at about 30 watts. So I tried a 100 watt incandescent, and the lamp ran up to about 70 volts (at about 38 watts) before the arc extinguished. Darn. Would have been very promising had it been able to run up all the way, as lamp power would have been about 45 watts and run-up time less than 5 minutes - way better than any fluorescent lamp ballast.

IMG_0784.JPG IMG_0639~0.JPG IMG_0610.JPG IMG_0549.JPG

Light Information

Light Information

Lamp
Lamp Type:Mercury vapor
Fixture
Ballast Type:Incandescent
Electrical
Voltage:120V

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Filename:IMG_0610.JPG
Album name:themaritimegirl / Experiments, Projects, & Mods
Keywords:Lamps
File Size:210 KB
Date added:Jan 18, 2014
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dor123
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Jan 18, 2014 at 10:59 PM Author: dor123
120V self ballasted mercury lamps, usually haven't any auxiliary electrodes at all, because of ignition problems at 120V. Instead they have small filaments that preheats the main electrodes and a bi-metal that disconnects them and strikes the arc.
I don't expect that your lamp would even start with an incandescent lamp at your main voltage.

I"m don't speak English well, and rely on online translating to write in this site.
Please forgive me if my choice of my words looks like offensive, while that isn't my intention.

I only working with the European date format (dd.mm.yyyy).

I lives in Israel, which is a 230-240V, 50hz country.

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Jan 18, 2014 at 11:12 PM Author: rjluna2
You would have to use low voltage incandescent light bulb, say about 60 volts to make this work. You should calculate how much voltage drop it needed to sustain enough voltage drop on the arc. Try this equation: Vout = (Z2 * Vin) / (Z1 + Z2)

http://en.wikipedia.org/wiki/Voltage_divider

Pretty, please no more Chinese failure.





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Jan 18, 2014 at 11:54 PM Author:
Technically it's not impossible to drive a standard mercury lamp in series with an incandescent ballast from 120V mains but the issues are that ignition with the auxilliary probe is very unreliable at such low voltage, and the proper current regulation of the mercury discharge requires that its arc voltage be not higher than about half of the mains voltage - that's why your lamp could not exceed 65V before it extinguished.
The reason for this condition is that on AC circuits discharge lamps extinguishe at each zero-crossing of the current and the discharge needs to be re-ignited after the current polarity change. This cyclic re-ignition requires a higher voltage level than the normal rms maintaining voltage (i.e. the RMS value that you usually measure with your voltmeter).
themaritimegirl
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Jan 19, 2014 at 05:58 AM Author: themaritimegirl
For some reason I haven't gotten any notification of comments being posted here, and they aren't showing up on the home page.

Dor: Indeed, it's not really supposed to be possible to strike on 120V. I did have to flip the switch on the power bar I used a few times before it struck.

rjluna2: The problem with the arc extinguishing is, as Max pointed out, that the arc voltage of a mercury vapor lamp is simply too high, at 100 volts or so. The general rule is that arc voltage can't be more than half of the open-circuit voltage to run reliably. That's why the F20T12, which has an arc voltage of around 60 volts, can run on choke ballasts, but the F30T12, which is 90 volts, generally can not. Also, a 60 volt bulb would probably burn out upon start-up, as a cold mercury vapor lamp has an arc voltage of less than 20 volts, dropping over 100 volts on the incandescent lamp.

Max: What I meant was the first time it hit 65 volts, it kept running, but the voltage didn't raise any higher due to, I assume, not enough current. The second time it ran up to 70 volts, and would've kept going, but of course hit the OCV threshold.

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Apr 05, 2014 at 06:19 AM Author: Globe Collector
I managed to pull of a High Pressure Sodium in series with a carbon filament off 240v @ 50Hz, albiet for only 10 seconds or so!

http://www.lighting-gallery.net/gallery/displayimage.php?album=229&pos=0&pid=92419

Manufactured articles should be made to be used, not made to be sold!

Fee, Fye, Fow, Fum, A dead man's eye and a parrot's BUM!

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Apr 05, 2014 at 06:29 AM Author: Globe Collector
I managed to pull of a High Pressure Sodium in series with a carbon filament off 240v @ 50Hz, albiet for only 10 seconds or so!

http://www.lighting-gallery.net/gallery/displayimage.php?album=229&pos=0&pid=92419

Manufactured articles should be made to be used, not made to be sold!

Fee, Fye, Fow, Fum, A dead man's eye and a parrot's BUM!

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