Metal Halide Bulb without Ballast

inetdog

Well-known member
Joined
Mar 4, 2013
Messages
442
hi guys ,
I got a sample metal halide bulbs which works without ballast i saw that it does have a halogen bulb inside with metal ,but i do not understand how it works ,
anybody have idea?
product like this :
http://www.alibaba.com/product-detail/400W-metal-halide-lamp-without-ballast_709075927.html?s=p
Best Regards.
It looks like the halogen bulb is in series with the discharge lamp. That would allow it to act a very high temperature coefficient resistor to stabilize the current through the negative resistance characteristic of the discharge bulb.
Its efficiency will be lower than that of a ballasted MH, but the simplicity would give a cost advantage.
 

inetdog

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Mar 4, 2013
Messages
442
Yes but how are they achieving the initial arc strike? Cap of some sort that I couldn't see?

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My guess is that the gas pressure in the MH capsule is tuned for just the peak of the applied line voltage being high enough to strike.
Since the halogen filament will be dead cold at that point you can pump a lot of energy into the MH in the first few cycles of the AC.
 
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sven_m

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Joined
Jul 11, 2009
Messages
92
Location
Southern Germany
As I undertand it:
There's also an auxiliary electrode at the bottom with a very small gap to the main electrode.
This small gap ignites even at mains voltage and doesn't require any special gas pressure
or additional components in the bulb for arcing. The little arc soon ionizes enough gas inside the bulb
for igniting the main arc. The little resistor limits the current through the auxiliary electrode.

I wonder about the possible purposes of the filament bulb,
- additional regulation of the initial current through the auxiliary arc with its initially low resistance
- some stabilization of the main arc current
- ...
 

zihuatanejo

Member
Joined
Aug 20, 2013
Messages
18
Location
Turkey
After long time process and getting expert confirmation, i realized that halogen works as a ballast, after long time(enough ignition time) halogen bulb light off it just emits tiny red light which is current flowing through filament, and just arc tube emits alone, but as inetdog mentioned those bulbs are not efficient as normal MH because of halogen bulb,
Best Regards.
 
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