Page 438 - Basic Electrical Engineering

To derive the relation between I and I , apply KCL at node R, as shown
L
Ph
in Fig. 4.9 (b)

I + I = I RY
BR
R
∴ I = I RY − I BR
R

Similarly at node Y and B, we can write

I = I YB – I RY
Y
I = I – I YB
BR
B
Since phase angle between phase currents I RY and −I is 60°
BR

Thus, for a three-phase delta-connected system,

Line current = × Phase current
Line voltage = Phase voltage

Power: Power output per phase = V I cos ϕ
Ph Ph
Total power output = 3V I cos ϕ
Ph Ph

Power = × Line voltage × Line current × Power factor

For both star-connected and delta-connected systems, the total power P is