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Topic: Calling Electricians

Dino Everette
Phenomenal Film Handler

Posts: 1535
From: Long Beach, CA USA
Registered: Dec 2008

posted September 14, 2012 01:00 AM

OK I am getting myself confused on something...If you have a 5A transformer that is stepping down from 120v to 24v does that mean the total wattage it is capable of is 600w or 120w? [Confused]

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"You're too Far Out Miss Lawrence"

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Akshay Nanjangud
Jedi Master Film Handler

Posts: 637
From: Dallas, TX
Registered: Nov 2011

posted September 14, 2012 01:45 AM

Generally, the 5A is the output current. If this is the case, then the output voltage multiplied by the current would give us 120 W.

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Martin Jones
Phenomenal Film Handler

Posts: 1269
From: Thetford , Norfolk,England
Registered: May 2008

posted September 14, 2012 03:04 AM

Confirmed....120W.

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Retired TV Service Engineer
Ongoing interest in Telecine....

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Steve Klare
Film Guy

Posts: 7016
From: Long Island, NY, USA
Registered: Jun 2003

posted September 14, 2012 08:15 AM

Usually transformers are rated in Volt-Amperes (sort of like "Watts" but not exactly, it depends on what kind of load they are driving)

Is there a VA rating for this transfomer that you can see?

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All I ask is a wide screen and a projector to light her by...

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Dino Everette
Phenomenal Film Handler

Posts: 1535
From: Long Beach, CA USA
Registered: Dec 2008

posted September 14, 2012 11:28 AM

I am just trying to choose the proper transformer to power 24v 300w lamp..

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"You're too Far Out Miss Lawrence"

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Steve Klare
Film Guy

Posts: 7016
From: Long Island, NY, USA
Registered: Jun 2003

posted September 14, 2012 11:50 AM

This character will do the job:

24VAC 400VA Transformer

It's capable of 400VA. You will use 300VA, but running power electronics flat out means they run hot, which means they won't last as long.

This is a dual primary and dual secondary transformer. To operate at 115VAC input you put the primaries in parrallel (To operate at 230, in series). For 24VAC you put the secondaries in parallel.(48 in series)

You’d need to put it in some sort of case, a pretty rugged one considering the weight of something like this (almost 10 Lbs.).

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All I ask is a wide screen and a projector to light her by...

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Manuel Tapia
Film Handler

Posts: 47
From: Monterrey, mexico
Registered: Aug 2012

posted September 14, 2012 12:08 PM

The transformer are quite expensive and big, look for a electronic transformer could be cheaper and small, if you are doing a lamp conversion, maybe you can try a 120V Lamp.

http://www.ebay.com/itm/EWG-120-VOLT-300-WATT-PROJECTOR-LAMP-PROJECTION-BULB-EIKI-16MM-120V-300W-/200750156928?pt=LH_DefaultDomain_0&hash=item2ebda44c80#ht_500wt_969

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Steve Klare
Film Guy

Posts: 7016
From: Long Island, NY, USA
Registered: Jun 2003

posted September 14, 2012 12:24 PM

Another transformer could be cheaper if for example you found one used, but it can't be too much lighter or smaller.

-as Scotty said:

"I canna change the laws of physics!"

You want it to run cool, which means fatter wiring and a heavy metal core.

-and you run cool or pretty soon you won't be running at all!

A 24V(dc) 300W electronic power supply runs $447 in single piece quantities:

300W 24VDC

(Old employer of mine, actually...)

and gives you the bonus of a fan whining in the background.

Power has gotten cheaper, but it still ain't cheap.

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All I ask is a wide screen and a projector to light her by...

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Dino Everette
Phenomenal Film Handler

Posts: 1535
From: Long Beach, CA USA
Registered: Dec 2008

posted September 14, 2012 01:26 PM

Steve what about something like this? It even looks like it has a built in fan.

24V 20A transformer

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"You're too Far Out Miss Lawrence"

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Steve Klare
Film Guy

Posts: 7016
From: Long Island, NY, USA
Registered: Jun 2003

posted September 14, 2012 02:40 PM

It's a little generic Far-Eastern looking, but then again given the price I really doubt you can go too wrong with it, especially since you'll be running at a little more than half rated power.

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All I ask is a wide screen and a projector to light her by...

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Dino Everette
Phenomenal Film Handler

Posts: 1535
From: Long Beach, CA USA
Registered: Dec 2008

posted September 14, 2012 03:36 PM

OK I'm gonna give it a shot...thanks for the help Steve....

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"You're too Far Out Miss Lawrence"

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