Ohms law 3 phase Resistance.

[brother]

Im curious when using ohms law formula on 3 phase circuits/transformers. do you still use E(squared) / watts (power) or E/I= R ?? or is 1.73 come into play here?

lets say you have a 15kva 480 primary 120 208 secondary 3 phase transformer and you want to know the resistance on it.

so 15000/(480 X 1.73)= 18.06 amps

480 volts /18.06 amps=26.578 Ohms (resistance) is this correct??

 

[coulter]

on 3 phase circuits/transformers. do you still use E(squared) / watts (power) or E/I= R ?? or is 1.73 come into play here

Balanced 3ph resistive load? I'd probably attack it single phase.


delta connected:
15kw (not kva) is 5kw between phases
I (through each 5kw resistor) = 5kw/480V = 10.4A (note this is not the phase current)
R (each one) = (480^2)/5kw = 46.1 ohms

Wye connected:
15kw is 5kw between each pase to neutral
I through each 5kw resistor = 5kw/(480/1.732) = 5kw/277 = 18.1A
R = (277^2)/5kw = 15.3 ohms

Yes, sqr(3) pops up everywhere.

carl