# Metal Halide Bulb without Ballast



## zihuatanejo (Jun 24, 2014)

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.


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## inetdog (Jun 24, 2014)

zihuatanejo said:


> 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 :
> ...


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.


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## FRITZHID (Jun 24, 2014)

Yes but how are they achieving the initial arc strike? Cap of some sort that I couldn't see?

Sent from my SAMSUNG-SM-G730A using Candlepowerforums mobile app


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## inetdog (Jun 24, 2014)

FRITZHID said:


> Yes but how are they achieving the initial arc strike? Cap of some sort that I couldn't see?
> 
> Sent from my SAMSUNG-SM-G730A using Candlepowerforums mobile app


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 (Jun 24, 2014)

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
- ...


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## zihuatanejo (Jun 25, 2014)

thanks guys for the ideas,
i have also asked a seller who produce it , he says halogen works as ignitor, after arc tube lighted on halogen will be light off,
but i have tried it in that way it did not happen like that , halogen still works after arc tube light on ? :duh2:
http://s24.postimg.org/jnx278qit/photo1_5.jpg 
best regards.


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## Onestep (Jun 25, 2014)

Was that fully up to temp or just shortly after ignition?


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## zihuatanejo (Jun 25, 2014)

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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## sven_m (Jun 25, 2014)

zihuatanejo said:


> http://s24.postimg.org/jnx278qit/photo1_5.jpg



can you make such a detailed picture with the bulb switched off?
This would allow to follow possible current paths without guessing
like in the alibaba picture.


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## asimzb (Jul 28, 2021)

would you please upload the picture ? the original product page is missing and i cant see which bulb is this? i wanted to buy a G12 MH lamp and seller says it works without ballast, but it looks like true metal halide bulb. i don't understand how ? here is the link https://www.aliexpress.com/item/32871978338.html


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