Page 436 - Basic Electrical Engineering

line voltages have been drawn. The phase currents I , I , and I have been
Y
B
R
shown lagging the phase voltages by the power factor angle ϕ.
From the phasor diagram shown in Fig. 4.6 (b), the phase angle between
phasors V and (–V ) is 60°.
Y
R

Thus, for the star-connected system

Line Voltage = × Phase voltage
Line Current = Phase current

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

P = VL IL cos ϕ (4.5)

4.5.4 Relationship of Line and Phase Voltages and Currents in a Delta-
connected System

Consider the balanced delta-connected system as shown in Fig. 4.9
In a delta-connected system the voltage aeros the winding, i.e., the phases
is the same as that across the line terminals. However, the current through the

phases is not the same as through the supply lines.
Therefore, in the case of the delta-connected circuit, phase voltage is equal

to the line voltage, but line current is not equal to phase current.