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Old 03-10-2020, 01:26 PM   #1
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Default 3 phase transformer for 1 phase power

Any body out there recommend using a 480 3 phase transformer for 1 phase lighting loads. I Have a customer who wants to use a three phase transformer to supply a 240/120 1 phase panel board. Iv'e always used a single phase transformer for this. I guess it's possible but is it correct, efficient and safe?
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Old 03-10-2020, 01:46 PM   #2
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No.

It's stupid.
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Old 03-10-2020, 01:49 PM   #3
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Quote:
Originally Posted by telsa View Post
No.

It's stupid.
Why ?

480/120/208V
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Old 03-10-2020, 03:22 PM   #4
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You end up with chronic circulating losses. That power bill adds up.

What a climate crime!

If you're going with a 3-phase transformer -- set a 3-phase panel.
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Old 03-10-2020, 04:11 PM   #5
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I could not make any sense out of it either. Business owner says he has friends telling him it will work. So at the risk of losing the job I suggested he should have his friend install it. A three phase panel is not an option these are existing panels on a single phase feed that is going to be replaced be three phase 480/277.
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Old 03-10-2020, 05:26 PM   #6
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I had a customer over a period of 50 years. He has died now. He was obsessed with auctions, or he'd always cruise around raiding construction dumpsters.

Always had a three phase 600 Volt industrial panel to install in his dairy barn. He never could understand why it wasn't good enough. It usually ended in me refusing to install.

Nothing unusual about a three phase transformer reducing voltage to 240/120 or 208/120 for single phase loads.
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Old 03-10-2020, 05:33 PM   #7
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Quote:
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I could not make any sense out of it either. Business owner says he has friends telling him it will work. So at the risk of losing the job I suggested he should have his friend install it. A three phase panel is not an option these are existing panels on a single phase feed that is going to be replaced be three phase 480/277.

Huh
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Old 03-10-2020, 06:11 PM   #8
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If it's my design, a single phase transformer of 10 KVA or below is ok but if it's 15 KVA or higher, it'll be 3Ø.
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Old 03-10-2020, 06:29 PM   #9
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Just use a 3ph panel for better load distribution.


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Old 03-10-2020, 06:39 PM   #10
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Lights belong on 277 VAC L-N -- straight up.
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Old 03-10-2020, 07:18 PM   #11
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Not only does using 2 legs of a 3Ø Y look like the installer was a complete idiot but it'll be hard on the transformer. They like all 3 currents to be somewhat balanced.

I notices you stated panels......more than 1? If so, then it is perfectly fine to have 2 or more single phase panels on a 3 transformer. Balance the panels among the 3 phases so one leg isn't heavy or light.
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Old 03-10-2020, 07:31 PM   #12
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Quote:
Originally Posted by micromind View Post
Not only does using 2 legs of a 3Ø Y look like the installer was a complete idiot but it'll be hard on the transformer. They like all 3 currents to be somewhat balanced.

I notices you stated panels......more than 1? If so, then it is perfectly fine to have 2 or more single phase panels on a 3 transformer. Balance the panels among the 3 phases so one leg isn't heavy or light.


I’ve seen the B to C phase jumper to energize the C phase


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Old 03-10-2020, 07:37 PM   #13
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Quote:
Originally Posted by myenergy View Post
I could not make any sense out of it either. Business owner says he has friends telling him it will work. So at the risk of losing the job I suggested he should have his friend install it. A three phase panel is not an option these are existing panels on a single phase feed that is going to be replaced be three phase 480/277.
WILL work, sure. But as tesla said, you will have the magnetic and hysteresis losses of a 3 phase transformer with the performance of a single phase. Over a relatively short time those extra losses will add up to MORE than what it would cost to just buy a single phase transformer. So he will be paying for the gear once, or paying for the wasted energy forever.


Just because you can doesn't mean you should...
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