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I
R
=
10
∠-
30
°
A rms, 
I
B
=
12
∠
130
°
A rms. Find the three-phase active power and reactive power delivered by the source. Draw the 
phasor diagram showing phase voltages, line voltages and line currents.
14. A delta-connected voltage source with zero source impedance delivers 
I
R
=
5
∠-
40
°
A rms, 
I
Y
=
15
∠-
100
°
A rms. The source that is directly between R-line and Y-line is found to deliver 
11
∠
0
°
A rms. 
V
RY
and 
V
YB
are found to be 200
∠-
0
°
V rms and 200
∠-
110
°
V rms, respectively. 
(i) Find the three-phase active power and reactive power delivered by the source. (ii) Find a delta-
connected impedance that will cause this loading in the source. (iii) Draw the phasor diagram 
showing phase currents, line currents and line voltages.
15. A star-connected balanced voltage source of 400 V rms, 50 Hz rating delivers 6
-
j3 kVA 
of complex power to a passive balanced Y-connected load. Use the R-phase phase voltage 
as reference phasor. (i) Find the line currents. (ii) Determine the load impedance. (iii) Draw 
the phasor diagrams showing all phase voltages, line voltages and line currents. (iii) What 
will be the readings in two wattmeters in two-wattmeter method of power measurement as in
Fig. 8.7-1?
16. A star-connected balanced voltage source of 400 V rms, 50 Hz rating with a source impedance 
of 1
+ 
j1 
W
in series with the source in each phase delivers power to a delta-connected balanced 
load impedance with a branch impedance of 20
+ 
j20 
W
at 50 Hz. Find the three-phase complex 
power delivered to the load.
17. A delta-connected balanced voltage source of 200 V rms, 60 Hz rating with zero source 
impedance delivers power to a delta-connected balanced load impedance with a branch impedance 
of 8
-
j6 
W
through an impedance-less connection. Find the line currents, load-branch currents 

---

8.40


SinusoidalSteady-StateinThree-PhaseCircuits
and three-phase complex power delivered to the load without transforming the circuit into its Y-Y 
equivalent. Draw the phasor diagram for the circuit taking