Three-Phase Line Current
Three-Phase Line Current
Sizing cables and protection for a three-phase load starts from its line current, found from the power and line voltage.
The line current is I = P/(√3·V·cosφ). where P is the real power, V the line voltage and cosφ the power factor.
Inputs
P := 15000 W=15000 W
V := 400 V=400 V
pf := 0.85=0.85
Invert the three-phase power relation for current.
I := P/(sqrt(3)·V·pf)=25.47 A
Results
This current sizes the conductors, breaker and overloads. A lower power factor raises it for the same real power, demanding larger cables.
Assumptions & limitations
- Balanced three-phase load.
- Line voltage and current.
- Sinusoidal steady state.