480v 3 phase to 110/220 single phase 50 amp panel

[chefiam1]

how do i come off of a 480v 3 phase panel to a small type transformer to get 110/220 single phase 50 amp panel. i need to know what to look for first and how many kva. do you use one leg of the 480v? just a very old electrician that has forgot!!

thanks, Chef

 

[LarryFine]

You will need a 2-pole breaker, only two wires (no neutral) plus ground, and a 480-to-120/240v 1ph transformer.

50a at 240v is 25a at 480v, which is 12 kva. The secondary neutral will require a grounding-electrode connection.

 

[mikeames]

What is your calculated load? The panel may be rated at 50A but what will be on it?

Assume you need 50 amps
You only want single phase, so you could use a 277v primary or a 480v primary. That would determine a single pole or a double pole. here's a 277v 15 KVA primary single phase. https://www.amazon.com/General-Duty-Transformer-Primary-Voltage/dp/B071P2BPRM

50x240 = 12KVA

12kva/277 = 43.3A primary current
450.3b more than 9 amps 125% of 43.3A = 54.1 amps you can go up to next standard size

 

[chefiam1]

5- 110v plugs, 3-4ft fluorescent lights. the 480 is going to feed a 3 phase pump that will draw 35-40 amps. i would like to have
220 in the building if it was ever needed. but if not how do you tap into the 480 v panel?

 

[chefiam1]

You will need a 2-pole breaker, only two wires (no neutral) plus ground, and a 480-to-120/240v 1ph transformer.

50a at 240v is 25a at 480v, which is 12 kva. The secondary neutral will require a grounding-electrode connection.

basically the 220 single phase panel needs it's own ground?on the 480 panel what do you do?

 

[infinity]

basically the 220 single phase panel needs it's own ground?on the 480 panel what do you do?

Since you have a SDS (the transformer) you'll need to connect the neutral point of the 120/240 volt secondary to a grounding electrode.

 

[Jraef]

Transformers come in standard sizes, a 15kVA 480-120/240 single phase transformer will give you 62.5A Full Load for the 120/240 panel.
480V primary current will be 31.2A, so I would put in a 40A 2P breaker in your 480V panel to feed it.

 

[chefiam1]

thanks