Getting 240V 3Ph for equipment

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Bwear

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Wisconsin
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Electrician Apprentice
Just trying to get some clarification. If I have a piece of equipment that needed 240V 3Ph 75A. And I don't have any 3ph 240V available. Would the best choice be to come out of a 480V Bus Duct and install a 480-240 xfmr to a disconnect fused at 75A to supply that equipment?
 
The only other choice would be a generator, so yes, that’s how it is typically done. You need primary protection off of the bus duct, then to the transformer, then from the secondary to the fused disconnect, then to your load.
 
If you decide to go with a transformer, consider one with a 3-phase 4-wire output, like a 240Y/136 volt or 240/120 center tapped delta output, rather than a more typical 240V delta 3-phase 3-wire output.

You may not find one on your distributor's shelf, but it worth ordering one due to the issues with grounding a 3-wire output.
 
Jraef said:
It's ALWAYS worth checking first... I can't even count the number of times someone has wanted a transformer for some new piece of machinery, only to find out the motors were dual voltage.
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We bought an aircraft hanger last year, and it came with a aircraft power unit they had just installed, but never turned on because the breaker to the transformer would trip. They were back feeding a 480 to 120/208 transformer to get 480 to it. Looked at the name plate, and it was multiple rated, 480, 240, 208. It was wired for 480 from where it was previously installed. They had the transformer wired as a dead short! LOL! Took the transformer out, changed the voltage taps and fuses, power unit works fine! Luckily they didn’t damage the brand new transformer or the power unit they had just installed!
 
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