D deharoj Member Nov 12, 2007 #1 I have 3 ph 480V primary. I need to get 400A on the secondary (120v - 208v)> Can someone tell me the size of the transformer and what amperage my primary should be? Thanks in advance, I'm just checking myself. I came up with Primary amps at 175 and the transformer at 112kva.
I have 3 ph 480V primary. I need to get 400A on the secondary (120v - 208v)> Can someone tell me the size of the transformer and what amperage my primary should be? Thanks in advance, I'm just checking myself. I came up with Primary amps at 175 and the transformer at 112kva.
J jatrottpe Member Location NJ Nov 12, 2007 #2 400A per phase secondary 400A * 208V * 1.732 = 144.102kva ~ 150kva transformer Primary 144102 / (480 * 1.732) = 173a 150000 / (480 * 1.732 ) = 180a
400A per phase secondary 400A * 208V * 1.732 = 144.102kva ~ 150kva transformer Primary 144102 / (480 * 1.732) = 173a 150000 / (480 * 1.732 ) = 180a
charlie b Moderator Staff member Location Lockport, IL Occupation Semi-Retired Electrical Engineer Nov 12, 2007 #3 I agree with jatrottpe's math. Please note, however, that the values of 400 (secondary) and 180 (primary) are the transformer's approximate current ratings, not the ratings of the associated overcurrent protection device.
I agree with jatrottpe's math. Please note, however, that the values of 400 (secondary) and 180 (primary) are the transformer's approximate current ratings, not the ratings of the associated overcurrent protection device.
M micromind Senior Member Location Fernley, NV. (near Reno) Nov 12, 2007 #4 The primary (480) current on a 112 KVA xfmr is 135 amps; the secondary current is 312. On a 150 KVA, it's 180 and 416.
The primary (480) current on a 112 KVA xfmr is 135 amps; the secondary current is 312. On a 150 KVA, it's 180 and 416.