3+ Amps Per +
3+ Amps Per +
(OP)
Ok, I am a bit embarrassed to ask this but I am totally confused. I recently installed a 500 KVA 277/480 padmount transformer. The question arose when I needed to size the CT loops for the new load. How many amps per phase is a 500KVA Tx capable of. The formula I use to find amps is:
I=VA/V(line to line) x 3^(1/2)
In this case the above would yield:
500,000/(480 x 1.73)= 602 Amps
Is the amps per phase 1/3 of this? or is 600A the amps per phase?
Any insight on this would be appreciated, 3Ø has always confused me.
Also, if the customer has an 800 amp 3Ø main disconnect, is that the rating per Ø or total of the Ø's?
Tom
I=VA/V(line to line) x 3^(1/2)
In this case the above would yield:
500,000/(480 x 1.73)= 602 Amps
Is the amps per phase 1/3 of this? or is 600A the amps per phase?
Any insight on this would be appreciated, 3Ø has always confused me.
Also, if the customer has an 800 amp 3Ø main disconnect, is that the rating per Ø or total of the Ø's?
Tom






RE: 3+ Amps Per +
You can arrive at the same conclusion, if you do a single phase calc using the load per phase and the voltage per phase.
3-phase 500 kva is 167kVA per phase and the voltage per phase would be 480/1.732 or 277V. Do the math for per phase or single phase current.
Current rating for three phase equipment is for the current in each phase or line.
RE: 3+ Amps Per +
Bill
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"Why not the best?"
Jimmy Carter
RE: 3+ Amps Per +
Tom
RE: 3+ Amps Per +
RE: 3+ Amps Per +
3 phase power = SQRT(3) x V (line to line) x I (line)
or
3 phase power = 3 x V (line to neutral) x I (line)
or
1 phase power = V(line to neutral) x I (line)
look at it either way, current is always per phase.