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#### Carandorandy

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8 Posts
Discussion Starter · ·
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.

#### darren

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##### Electrician
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1,404 Posts
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.

#### Carandorandy

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Discussion Starter · ·
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

#### J. V.

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5,406 Posts
Ohms law is all you need to figure this out. Do you have an "ohms law" circle.

Here is what it looks like.

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#### hhuggles

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Joined
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28 Posts
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
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.

#### nap

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##### You talking to me?
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7,551 Posts
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.

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