transformer

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DoggedLeg

Member
Location
Austin, Tx
Occupation
Journeyman
A friend of mine has a little industrial shop currently powered with 120/208 that now needs 240 and 480 to test big steamers, the biggest being a 54A 480v. The tests last about 1 minute just to ensure they're working.
The current panel is a 200 A being fed by 3/0 with a few 20 and 30a breakers feeding lighting and a couple fridges.
My question is, can i come out of a 125A breaker with 2 AWG to a the transformer (being installed 10 feet away in sight) through and to a 60A load size main?
There will be a few drop down plugs for testing but never be testing more than one at a time.

my math tells me that if i want to get 55 A out of the load side I need to send about 125A to the line, does this sound correct? thats how im sizing the breaker and the wire on line side.


for the 208-240v, i was going to order a 15kva 240-208 and flip the leads.

Does this all jive to yall?
 
If we are talking 3 phase, 54 amps would be a 45 kva trasnformer.
You would to make sure a 125 amp 3 phase breaker is available for your panel.
If you proceed I strongly suggest you get a step-up transformer (208-480Y277) rather than "reverse feed"
 
How are you going to get 240 and 480 out of the same transformer? Is this all single phase?
 
augie47 said:
If we are talking 3 phase, 54 amps would be a 45 kva trasnformer.
You would to make sure a 125 amp 3 phase breaker is available for your panel.
If you proceed I strongly suggest you get a step-up transformer (208-480Y277) rather than "reverse feed"
Click to expand...
Yes 3 phase 208 up to 480. I found another thread that mentioned the same thing, I’ll look into a 45kva step up. Thanks a lot.
If the existing panel doesn’t have the ability to host a 125a then a fused disconnect would suffice wouldn’t it?
 
DoggedLeg said:
It would be two separate transformers.
It’s 3 phase
Click to expand...
Ah okay, you only mentioned the 125 amp so it sounded like one transformer. So you have 208Y/120 and you need two transformers to provide both 3 phase, 240 volts and 480 volts?
 
DoggedLeg said:
A friend of mine has a little industrial shop currently powered with 120/208 that now needs 240 and 480 to test big steamers, the biggest being a 54A 480v. The tests last about 1 minute just to ensure they're working.
The current panel is a 200 A being fed by 3/0 with a few 20 and 30a breakers feeding lighting and a couple fridges.
My question is, can i come out of a 125A breaker with 2 AWG to a the transformer (being installed 10 feet away in sight) through and to a 60A load size main?
There will be a few drop down plugs for testing but never be testing more than one at a time.

my math tells me that if i want to get 55 A out of the load side I need to send about 125A to the line, does this sound correct? thats how im sizing the breaker and the wire on line side.


for the 208-240v, i was going to order a 15kva 240-208 and flip the leads.

Does this all jive to yall?
Click to expand...
tap into your existing 3/0 feeders to a 250v fusible 200amp disconnect and from there to your transformer ,i recommended 75kva due to the output rating of 90.A at 480v u will be able to install a 100 amp fusible disconnect and tap from the load side to each set equipment testing area
 
Step by step of electric said:
tap into your existing 3/0 feeders to a 250v fusible 200amp disconnect and from there to your transformer ,i recommended 75kva due to the output rating of 90.A at 480v u will be able to install a 100 amp fusible disconnect and tap from the load side to each set equipment testing area
Click to expand...
That’s an interesting option, so discos on both sides. Tapped into the incoming line of the panel, then out to a fusible disconnect where the plugs are all connected to load side. Thanks, I might run with this idea
 
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