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02-24-2011, 08:22 PM   #1
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## 3 KVa / formula

Doe's anyone know how to plan a 3 kva, line side fuse size?
Gotta Go will be back tomorrow to see results.
Thanks Carandorandy.

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02-24-2011, 09:27 PM   #2
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yes you figure out the amps, determine if it is a continous or non continous load and then determine from that what size fuse you need.

Your question is way to vague for anyone to give you the proper answer.

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02-25-2011, 10:49 AM   #3
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## Calculating Overcurrent Protection on the Primary Side

3 KVA dry type transformer (Calculating Overcurrent Protection on the Primary Side)?
I will run #12 THHN wire as we usualy do but the current on the load is some constant at about 1.5 amps for a low voltage power supply and the rest of the panel is floating at about 15 amps max using 480 single phase on the line side of the 3KVA.
Just wondering if I can calculate exactly what the transformer is going to draw?
Thanks
Carandorandy

 02-25-2011, 12:41 PM #4 Member   Join Date: Jun 2007 Posts: 3,709 Rewards Points: 78 Ohms law is all you need to figure this out. Do you have an "ohms law" circle. Here is what it looks like. Attached Thumbnails
02-25-2011, 03:49 PM   #5
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Quote:
 Originally Posted by Carandorandy 3 KVA dry type transformer (Calculating Overcurrent Protection on the Primary Side)? I will run #12 THHN wire as we usualy do but the current on the load is some constant at about 1.5 amps for a low voltage power supply and the rest of the panel is floating at about 15 amps max using 480 single phase on the line side of the 3KVA. Just wondering if I can calculate exactly what the transformer is going to draw? Thanks Carandorandy
More information is required.
480v single phase line side.
transformer connection type? single phase -> single phase?
What is the ratio of windings? (Will help to know the load voltage)
Once we know this then ohm's law will figue out the rest.

 02-25-2011, 07:46 PM #6 You talking to me?     Join Date: Dec 2007 Location: sw mi Posts: 7,551 Rewards Points: 6,290 you go and grab your little transformer slide rule thingy and look at what it says to use. To be able to even look it up on a chart, you need the voltage and single or three phase.
02-26-2011, 08:17 AM   #7
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Quote:
 Originally Posted by nap you go and grab your little transformer slide rule thingy and look at what it says to use. To be able to even look it up on a chart, you need the voltage and single or three phase.
Oh, man. It has been a LONG time since I seen one of those slide rule thingys. 20 yrs since I had one of those.

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