Hi everyone! Awhile back I got a 175 watt mercury vapor lamp and I tested it out on my rudemrntary ballast (a 25 and a 150 watt incandescent light in series with it) and it worked well, except for the fact it will run obout 5-10 mins and magically turn off. Do I need a proper ballast or is something wrong with the lamp, THX!
Need help with mercury vapor lamp
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You will need a proper ballast or fixture for your 175W mercury bulb.A simple resistive ballast (the incand bulbs) won't work well with HID type bulbs that are high wattage such as the one you have.Check around you for the proper ballast or fixture Often farm supply and electrical supply places can help.High wattage HID bulbs like yours need a magnetic--Transformer type ballast to start and function properly.Sadly mercury vapor bulbs are being phased out in favor of Metal Halide,High pressure sodium and LED lights.You will have to look around for a proper ballasted fixture-if you have a fixture with a bad ballast-than you will need a replacement one.175W mercury lights were popular at one time as barn and yard lights.These fixtures were quite common and show up used-or some hardware store might have a new one.Like mercury lights-they can give a nice daylight blue color.And they last for a long time.
This is what I think is what's happening
When the lamp first starts, it pulls a lot of power, making the ballast lights very bright. According to the rule of heating elements, as the element gets hotter, resistance decreases. Once the lamp has warmed up, the ballast lamps start cooling down, increasing the resistance in the lamp, apparently creating enough voltage drop that the arc cannot be sustained.
Also I think that mercury vapor lamps can run on metal halide ballast, obviously with the same wattage.
When the lamp first starts, it pulls a lot of power, making the ballast lights very bright. According to the rule of heating elements, as the element gets hotter, resistance decreases. Once the lamp has warmed up, the ballast lamps start cooling down, increasing the resistance in the lamp, apparently creating enough voltage drop that the arc cannot be sustained.
Also I think that mercury vapor lamps can run on metal halide ballast, obviously with the same wattage.
Yes,Mercury bulbs can run on the same wattage ballast as for MH bulbs.Check the ballast dataplate to make sure.Some MH ballasts can't be used with mercury bulbs.Usually the ballast plate indicates with the ANSI lamp type number and generic type.On the resistence of the bulbs you are using as a ballast-that would be correct-that is why you can't sustain the arc in your mercury lamp.Magnetic and solid state ballasts can compensate for these factors.And use less power.When resistors are used as ballasts usually with old carbon arc lamps and DC supplies-resistors are used.Was common in the motion picture lighting industry when their systems ran on 120/240V DC.You would see large resistor lighting ballast boxes at the bases of their lights Carbon arc-they called the ballasts "grids"They sort of looked like large heating elements.Now HMI,Xenon,LED lights are used.And now AC power for the motion picure light industry.
arbilab
Well-known member
The chaos of plasma (high-temp arcs) is such that at operating temperature the resistance of an arc lamp goes WAY up. So much so that if the arc fails at temperature it becomes impossible to restart until it has cooled.
Ballasts do more than dissipate cold-start current. A magnetic ballast stores energy to sustain the arc at line zero crossings. A resistive ballast does not. Electronic ballasts have negligible zero crossings on the order of microseconds as safe zones between FET conduction states.
That's real helpful, isn't it? I worked on magnetic and electronic ballasts in the 650-Watt range for a couple years in the 90s. Just enough to know how fyuking weird arclamp characteristics are. Not enough to tell you what you need to do, other than I NEVER saw a purely resistive ballast application.
Ballasts do more than dissipate cold-start current. A magnetic ballast stores energy to sustain the arc at line zero crossings. A resistive ballast does not. Electronic ballasts have negligible zero crossings on the order of microseconds as safe zones between FET conduction states.
That's real helpful, isn't it? I worked on magnetic and electronic ballasts in the 650-Watt range for a couple years in the 90s. Just enough to know how fyuking weird arclamp characteristics are. Not enough to tell you what you need to do, other than I NEVER saw a purely resistive ballast application.
I have listings for carbon arc resistive ballasts-grids in an old Mole Richardson lighting equipment-motion picure filming equipment catalog.they are in Hollywood,Calif.Requested one of their huge loose leaf ring binder catalogs sometime in the 70's-they were still selling carbon arc lighting equipment alongside HMI and Xenon lighting.And they had a 120/240VDC portable genset run by a Cadillac V8 motr in a soundproof enclosure for remote set lighting power.The book is interesting reading--but the prices on that equipment---wOW!!!!Now all of their gear runs from AC and no more carbon arc "Tenor,"Senior" lighting heads.
arbilab
Well-known member
I know next to nothing about xenon (except it tends to be DC) and even less about carbon (except it is always DC). Neither have to cope with zero crossings so pure resistance works fine.
this is straying far from Mercury lamps-Xenon lamps are still being used to light motion picture projectors. Earlier they were used to light film projectors.Now they are being used for digital projectors newly installed in theaters to replace the film ones.The bad thing about Xenon bulbs is they have a tendency to explode while lit! And you have to handle Xenos when unlit,too-they are at positive pressure and can explode in your hands-projectionists don heavy cloths and face mask while replacing them.When they do the bulb takes out the projectors reflector-Expensive or in the case of a digital projector-the light engine-the part that forms the picture.The light engine is even MORE expensive.The Digital projector ballasts keep time on the lamp.They have an indicator on the digital projectors built in monitor screen to alert an operator if the lamp has too many hours on it.If the operator ignores the warning-the timing system in the digital projector ballast may even prevent you from starting the lamp!You "reset" the timing system when you replace a lamp in the projector.Then there are plans of replacing the Xenon bulbs with lasers in the future.Would like to learn more how these laser lamphouses would work-and if there is a version to retrofit to older projectors.
Just got thru watching an excellent video of the operation of a Mole-Richardson "Brute" carbon arc light fixture for motion picure lighting.Search YouTube and I am sure you will find it.The person is associated with MR and gives an EXCELLENT demo of the lamp,its operation,and hookup-and shows the "grid" ballast.DC based lighting is used in motion picure lighting and projection-so you don't get light "aliasing" not sure of the spelling in the picure-flickering from the 60 hz light interfering with the shutter of the projector or camera.MR makes a 24Kw HMI light-would love to see this!!!These would run from AC I beleive and don't cause the interference.Some mad raccoon hunter would love to put one of those lights in the back of his pickup-that would be a coonlight!They would drop from the tree from blindness!!They can be run from a large genset.The HMI light and carbon arc one would be used for daylight fill lighting or giving daylight quality on indoor lighting-6K temp light.
Get you on the zero crossings!forgot that!!is a problem with AC indeed.Since ballasts are now going to high frequency-both flourescent and HID-the HF ballast gives better efficiency.So the zero crossings would be more frequent.So the inductance of the HF ballast would compensate.Have a couple HF ballasts for 400W lamps-it can run probe start MH bulbs,Pulse stat MH and HP sodium from one ballast.And no hum or buzz-Just a slight "ringing" sound as the lamp starts.Figure this is the arc tube structure in the bulb vibrating at the high frequency of the ballast.
Just got thru watching an excellent video of the operation of a Mole-Richardson "Brute" carbon arc light fixture for motion picure lighting.Search YouTube and I am sure you will find it.The person is associated with MR and gives an EXCELLENT demo of the lamp,its operation,and hookup-and shows the "grid" ballast.DC based lighting is used in motion picure lighting and projection-so you don't get light "aliasing" not sure of the spelling in the picure-flickering from the 60 hz light interfering with the shutter of the projector or camera.MR makes a 24Kw HMI light-would love to see this!!!These would run from AC I beleive and don't cause the interference.Some mad raccoon hunter would love to put one of those lights in the back of his pickup-that would be a coonlight!They would drop from the tree from blindness!!They can be run from a large genset.The HMI light and carbon arc one would be used for daylight fill lighting or giving daylight quality on indoor lighting-6K temp light.
Get you on the zero crossings!forgot that!!is a problem with AC indeed.Since ballasts are now going to high frequency-both flourescent and HID-the HF ballast gives better efficiency.So the zero crossings would be more frequent.So the inductance of the HF ballast would compensate.Have a couple HF ballasts for 400W lamps-it can run probe start MH bulbs,Pulse stat MH and HP sodium from one ballast.And no hum or buzz-Just a slight "ringing" sound as the lamp starts.Figure this is the arc tube structure in the bulb vibrating at the high frequency of the ballast.
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