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Lamp's Voltage?

lamp hmi volts

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#1 Rodolpho de Barros

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Posted 08 November 2014 - 04:05 PM

Hi,

I bought a 1.2kw HMI Fresnel with Ballast which works on 220v.

I saw for the first time when I was looking the especifications of the amps that there's a voltage, some are 110v, some 90v, some 110-200v AC. So I can't use a 110v Lamp in my 220v ballast?

I never thought that a lamp have a voltage.


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#2 Guy Holt

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Posted 08 November 2014 - 06:33 PM

Hi,

I bought a 1.2kw HMI Fresnel with Ballast which works on 220v.

 

What's the make and model of the ballast? Is it magnetic or electronic?

 

Guy Hoilt, Gaffer, ScreenLight & Grip, Lighting Rental & Sales in Boston


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#3 Rodolpho de Barros

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Posted 09 November 2014 - 10:32 AM

It's an eletronic ballast.

 

You can check out if you want

http://www.ebay.com/...=item46172e2124

 

It's an "as arri" from China. Do you know?

I bought to test it.

 

 

What's the make and model of the ballast? Is it magnetic or electronic?

 

Guy Hoilt, Gaffer, ScreenLight & Grip, Lighting Rental & Sales in Boston

 


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#4 Guy Holt

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Posted 09 November 2014 - 11:31 AM

It's an eletronic ballast.

 

You can check out if you want

http://www.ebay.com/...=item46172e2124

 

It's an "as arri" from China. Do you know?

I bought to test it.

 

 

 

I forgot to ask and it is not part of your profile, what the prevailing line voltage is in your country?

 

Guy Holt, Gaffer, ScreenLight & Grip, Lighting Rental & Sales in Boston


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#5 Rodolpho de Barros

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Posted 09 November 2014 - 11:52 AM

220v

 

 

 

I forgot to ask and it is not part of your profile, what the prevailing line voltage is in your country?

 

Guy Holt, Gaffer, ScreenLight & Grip, Lighting Rental & Sales in Boston


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#6 Rodolpho de Barros

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Posted 10 November 2014 - 10:50 AM

It's 220v.

So really there's a voltage for the lamp?

 

 

I forgot to ask and it is not part of your profile, what the prevailing line voltage is in your country?

 

Guy Holt, Gaffer, ScreenLight & Grip, Lighting Rental & Sales in Boston


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#7 Guy Holt

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Posted 10 November 2014 - 01:34 PM

It's 220v.

So really there's a voltage for the lamp?

 

 

Yes, the lamp operates at a different voltage than does the ballast. Electronic HMI ballasts are  a type of Switch-mode Power Supply (SMPS.) They, in fact, operate in a very similar fashion to electronic fluorescent ballasts. As you can see from the simplified schematic of an HMI ballast below, AC power is first converted into DC. Then, a high-speed switching device (micro processor controlled IGBTs) turns the DC current into alternating square wave. The difference between an electronic HMI ballast and an electronic fluorescent ballast is that the HMI ballast generates a low frequency square wave (typically 75Hz) where the electronic fluorescent ballast generates a high frequency sine wave (typically 20-40kHz).

 

squarewave_ballast_sch.jpg

 

The ballast not only reconfigures the frequency of the power to the lamp, it also changes the voltage at which the lamp operates as well (use this link for more details on how HMI ballasts work.) I am not personally that familiar with the Chinese knock-offs of the Arri ballasts so I can’t help you figure our which globe to use.  I would ask the manufacturer.

 

Guy Holt, Gaffer, ScreenLight & Grip, Lighting Rental and Sales in Boston


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#8 Rodolpho de Barros

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Posted 10 November 2014 - 02:20 PM

Thank you very much, Guy.

 

 

Yes, the lamp operates at a different voltage than does the ballast. Electronic HMI ballasts are  a type of Switch-mode Power Supply (SMPS.) They, in fact, operate in a very similar fashion to electronic fluorescent ballasts. As you can see from the simplified schematic of an HMI ballast below, AC power is first converted into DC. Then, a high-speed switching device (micro processor controlled IGBTs) turns the DC current into alternating square wave. The difference between an electronic HMI ballast and an electronic fluorescent ballast is that the HMI ballast generates a low frequency square wave (typically 75Hz) where the electronic fluorescent ballast generates a high frequency sine wave (typically 20-40kHz).

 

squarewave_ballast_sch.jpg

 

The ballast not only reconfigures the frequency of the power to the lamp, it also changes the voltage at which the lamp operates as well (use this link for more details on how HMI ballasts work.) I am not personally that familiar with the Chinese knock-offs of the Arri ballasts so I can’t help you figure our which globe to use.  I would ask the manufacturer.

 

Guy Holt, Gaffer, ScreenLight & Grip, Lighting Rental and Sales in Boston


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#9 George Suarez

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Posted 13 November 2014 - 01:31 PM

All ballasts increase the voltage over the lamp rating. The globe itself is what clamps the voltage down to what the globe is design to run at.

 

This is how you get the multi wattage ballasts. The easiest example is 12/18K, both run same head, connection, socket etc... the only difference is the globe. The 12K runs at about 160V and the 18K runs at 240V. The ballast provides 380V out. Both globe start running at about 30V and work up to the running voltage. From there the ballast will switch into 18K once it hits 190V with Arri and 200V with Powergems and Magnetic ballast or stay at 12K if it dosen't hit the voltage level.


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#10 Guy Holt

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Posted 13 November 2014 - 03:59 PM

All ballasts increase the voltage over the lamp rating. The globe itself is what clamps the voltage down to what the globe is design to run at.

 

Very true, which means that  the OP should be able to use a lamp rated for  either 110v or  90v in his head.

 

George, welcome to the boards. Your an asset to have and I look forward to hearing more of your input in the future. If you have a lead on bottom/side vents for an LTM18k Fresnel  contact me off-line (I have a 12k I want to upgrade to an 18k.)

 

Guy Holt, Gaffer, ScreenLight & Grip, Lighting Rental & Sales in Boston


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