480 wye to single phase 240/120

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Moosifer

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Panama City Beach, FL
What kind of transformer do I need to do this and is it possible or will I get 139v or something like that? Not my specialty and the transformer people don't seem to know much other than ask an electrician. I so hate it when people say that.
 
Since you only need 1ph, you only need a 1ph transformer. 480v (or 240/480v dual voltage in series) to 120/240v (either dual voltage in series or center tapped).
 
Most people do as Larry suggested just use two legs of 480.
How many kVA of 480 do you have to spare and whats the 120/240 load?
 
To a degree it will be based on your specific load (Total load and % 120v load).. You can install a 3 phase 240/120 Delta transformer but they are very restrictive on the 120v load (some about 5%) or you can, as suggested, install a single phase 240/120 transformer without the neutral restriction.
Ideally, if your loads could operate on 208v, you would install a 480/208Y120 transformer.


What is the size and configuration of your load ?
 
augie47 said:
To a degree it will be based on your specific load (Total load and % 120v load).. You can install a 3 phase 240/120 Delta transformer but they are very restrictive on the 120v load (some about 5%) or you can, as suggested, install a single phase 240/120 transformer without the neutral restriction.
Ideally, if your loads could operate on 208v, you would install a 480/208Y120 transformer.


What is the size and configuration of your load ?
Click to expand...
2 hvac units and a bunch of electronics, so not too sure it can work with 208. Hvac units are 230v. 80a max. The 120 side is more important so perhaps that is the best way to go and hope the hvac units can live on 208...
 
The way I look at it is you have 22.8 kVA of single phase load you want to add to 3 phase 480 system.
You need to look at the existing 480 configuration so see what fits best.
If you use a 25kVA single phase 480:120/240 transformer you'd be adding about 48 amps to two legs of your system.
You need to evaluate if the existing 480 bank can handle it and if you can balance that L-L 480 load.
That is a fairly simple cost effective install I have done many times.
Or you can use a more expensive 480D:208Y/120 three phase transformer to balance the load.
In that case your adding about 28 amps per leg balanced across the entire 480 bank.
 
You stated 2 HVAC units, 80 amps max... is that 80 amps total for both units ? Do you know the actual load, MCA etc ??
 
40a max for each of 2 AC units. It will be fed by a 100a extension cord. It turns out the hvac units can do 208. 120v load is computer stuff and a very small winch.
I was hoping this would work.
25 kVA 1-Ph Dry-Type Transformer
Primary Voltage: 480
Secondary Voltage: 208
Taps: 2A / 4B @2.5%
Conductor: Al/Al
Frequency: 60 Hz
Temperature Rise: 150°C
Insulation Class: 220°C
Class: ANN

Thoughts?
 
Moosifer said:
40a max for each of 2 AC units. It will be fed by a 100a extension cord. It turns out the hvac units can do 208. 120v load is computer stuff and a very small winch.
I was hoping this would work.
25 kVA 1-Ph Dry-Type Transformer
Primary Voltage: 480
Secondary Voltage: 208
Taps: 2A / 4B @2.5%
Conductor: Al/Al
Frequency: 60 Hz
Temperature Rise: 150°C
Insulation Class: 220°C
Class: ANN

Thoughts?
Click to expand...
You will need a three phase transformer if you need 120/208. You will not get 120 out of that transformer. If you use that transformer, you will need another one that is 208 to 120. Unless the 120 volt stuff is separate, it’s going to get messy.
 
Since your HVAC will operate on 208v I would suggest a 30kva 3phase 480-208/120 transformer feeding a 100 amp panel.
That way you could utilize your existing 60 amp breaker (assuming it's 3 pole) although a smaller breaker could be used and the 100 amp amp panel will meet the 125% secondary protection rule.
 
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augie47 said:
Since your HVAC will operate on 208v I would suggest a 30kva 3phase 480-208/120 transformer feeding a 100 amp panel.
That way you could utilize your existing 60 amp breaker (assuming it's 3 pole) although a smaller breaker could be used and the 100 amp amp panel will meet the 125% secondary protection rule.
Click to expand...
Ok sounds good, thank you.
 
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