Author Topic: Why the difference in Mercury and Metal Halide bulb shapes EU vs US?  (Read 110 times)
Bert Bright
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Why the difference in Mercury and Metal Halide bulb shapes EU vs US? « on: April 15, 2018, 08:32:54 PM » Author: Bert Bright
From what I've seen, clear Metal Halide and Mercury bulbs in Europe are usually Tubular, whereas in the US they seem to instead most of the time be Bulbous Tubes or Elliptical.

I was curious what the reasons for this might be?  Mercury Vapor Lamp
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dor123
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Re: Why the difference in Mercury and Metal Halide bulb shapes EU vs US? « Reply #1 on: April 15, 2018, 10:11:52 PM » Author: dor123
Mercury and metal halide lamps are different stories between EU and US.
European mercury lamps are elliptical, because all of them adopted /C and later /DX phosphor coating, and clear lamps became rare there. In the US, you have BT shaped mercury lamps and most of them are clear.
With metal halide lamps, most of the European metal halide lamps are tubular clear, but also elliptical coated. Also most of the EU metal halide lamps are pulse-start, since we uses series choke to run them. The American metal halide lamps, usually runs on autotransformer ballasts, since the mains voltage there is low (120V), so most of them are probe-start. Also, most American metal halide lamps are elliptical or BT shaped with clear finish.
Also: European metal halide lamps, adopted various halides chemistry, mainly tri-band indium-thallium-sodium. American metal halide lamps adopted sodium-scandium.
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Re: Why the difference in Mercury and Metal Halide bulb shapes EU vs US? « Reply #2 on: April 17, 2018, 12:39:48 PM » Author: Ash
Dor I still dont understand why the shapes were chosen like that, even with your explanation :

 - In the US clear lamps, why was the BT shape used ? If only to keep the same bulb as the phosphored types (to let them go through the same machinery without changes), then were the first clear lamps in the US a T shape too ?

 - In the phosphored lamps, both BT and E/ED shapes provide acceptable performance, so this still does not explain completely why one was chosen over another differently in different countries ?
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