What's the operating voltage of mercury vapor lamps? Is it different for different wattages? If so, the lamps I specifically wanna know the voltage for are 50W and 175W. This info would be useful for some experiments I wanna get started.

Thanks.

I never tried 50 watt lamps, but 175 watt lamps are usually around 130 volts at full warm up. The lamp current ranges from 1.2 to 1.4 amp depending on the ballast. The ballast open voltage ranges from 215 volts to 250 volts for H-39 (mercury) ballast and around 300 volts for M-57 (175w metal halide).

I also noticed other wattages like 100w and 400w also have full run-up lamp voltage of around 130. Any of these lamps could be as low as 125v, and as high as 135v depending on a bunch of variables. But the most critical thing is lamp current...that's one reason the ballast is so important!

Yeah I was gonna figure the current from the voltage. From what you've said I can figure the ideal current for a 175 watt merc at 130 volts would be 1.35 amps (which backs up your current ratings). Using this I can figure the ideal resistance for a resistive ballast (I'll figure that later). From the looks of it, I'll probably have to either use a 240 volt source or a step up for a 175 watt lamp, seeing as a resistive ballast at 120 volts would have too low of a voltage to keep the lamp stable. I'm thinking a 50 watt lamp has a lower voltage, probably around 80, maybe as high as 100, which would be relatively easy to drive from 120 volts using a resistive ballast. In case you didn't know, I intend to use an incandescent lamp as a resistive ballast, as an incandescent lamp acts like a light emitting resistor. And yes, I'm aware I'm going to have to use some kind of HV source to strike the arc.

Interesting idea. A resistive ballast won't be efficient though since the voltage drop across it times the current will be lost wattage as heat (and light if you use incandescent bulb). Also, if you decide to use a 240 volt circuit, and decide to try and incandescent lamp, use a 240 volt bulb because when the MV lamp first strikes, it will only have about 17 volts across it and the ballast will have the remaining voltage....around 223v across it until the lamp warms up . Not sure what wattage incandescent lamp to use though.

Yeah, for the 240 volt circuit I was planning on using two identical 120V incands in a series. The same as a 240 volt lamp, without requiring me to find a 240 volt lamp.

I'm aware that it's gonna be inefficient but that doesn't mean it won't be fun! I can figure the wattage needed by measuring the impedance of different lamps and matching the closest one to my calculated ideal impedance. I can also fine tune it by using very low wattage lamps in parallel with the high wattage ones.

Although I'll probably do it the more fun way... Start with low wattage lamps and work my way up until the voltage and current to the MV lamp is near ideal, then do some fine tuning.

That's how I managed to ballast an F20 lamp with a 60 watt incand lamp. If you wanna try it, keep in mind you need about 100 watts of incand lamps to start the F20 lamp, but you need to drop it quickly to a 60 watt lamp once it's started. This can be done by using a 60 watt and a 40 watt lamp in parallel, and disconnecting the 40 watt lamp after the F20 is started. This was arranged in a standard preheat circuit, but with the incand lamps in place of the ballast. As an alternative, you can use just a 60 watt incand as the ballast, and an HV source to start the F20 lamp.

A 50w mercury lamp is 90v at full brightness, FYI. 75-400 watt mercury lamps operate at 130 volt. H-34 ballasted 1000 watt merc lamps operate at 130 volt also. For the 700w and more common H-36 ballasted 1000w lamp, operating voltage is 250 volt.

This topic wouldof been useful.. if i wouldof found it a bit more early when i was dinking around with ballasting a MV or HPS lamp on incandescent lamps...