Network Analysis and Synthesis, 1st Edition by Pearson

Three-phase Systems and Circuits 365

9.5.3 Relationship of Line and Phase Voltages and Currents

in a Star-connected System

Consider the balanced star-connected system as shown in Figure 9.9.

Suppose, the load is inductive and, therefore, current will lag the applied voltage by an angle f.

Consider a balanced system so that the magnitude of current and voltage of each phase will be

the same.

That is, phase voltages, V

R

= V

Y

= V

B

= V

Ph

Line current I

R

= I

Y

= I

B

= I

L

Line voltage V

L

= V

RY

= V

YB

= V

BR

Phase current I

Ph

= I

R

= I

Y

= I

B

I

L

= I

Ph

for star connection as the same phase current passes through the lines to the load.

I

R

I

R

V

R

V

B

V

B

−V

B

−V

R

V

Y

N

N