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ASSINGMENT 1 – THREE PHASE SYSTEM
Question 1
For the Y-Y circuit of Figure 1 below, find the line currents, the line voltages and the
load voltages.
Figure 1
Question 2
In the Y- system shown in Figure 2 below, the source is Van = 1200 V and
phase impedance Zp = 2 – j3. Calculate the line voltage VL and the line current IL.
Figure 2
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Question 3
Refer to the - circuit in Figure 3 below. Find the line and phase currents. Assume
that the load impedance is ZL = 12 + j9 per phase.
Figure 3
Question 4
For the balanced circuit in Figure 4, Vab = 1250 V. Find the line currents IaA, IbB, IcC.
Figure 4
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Question 5
A 208-V three phase power system is shown in Figure 5. It consists of an ideal 208V Y-connected three-phase generator connected through a three phase
transmission line to a Y-connected load. The transmission line has an impedance of
0.06 + j 0.12  per phase and the load has an impedance of 12 + j9 per phase. For
this simple power system, find
a)
b)
c)
d)
e)
f)
g)
The magnitude of line current IL
The magnitude of the load’s line and phase voltages VLL and VL
The real, active and apparent powers consumed by the load
The power factor of the load
The real, reactive and apparent powers consumed by the transmission line
The real, reactive and apparent powers supplied by the generator.
The generator’s power factor
Figure 5 (a) Three-Phase Y-Y Circuit
Figure 5 (b) Per-phase circuit
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