Basic AC Power
THREE-PHASE CIRCUITS
As you can see, the total power formulas for
Figure 13 3f Power Triangle
delta- and wye-connected loads are identical.
Total apparent power (ST) in volt-amperes and
total reactive power (QT) in volt-amperes-reactive
are related to total real power (PT) in watts
(Figure 13).
A balanced three-phase load has the real,
apparent, and reactive powers given by:
PT
3 VTILcosq
ST
3 VTIL
QT
3 VTILsinq
Example 1: Each phase of a delta-
Figure 14 Three-Phase Delta Generator
connected
3f
AC
generator
supplies a full load current of 200
A at 440 volts with a 0.6 lagging
power factor, as shown in Figure
14.
Find: 1. VL
2. IL
3. PT
4. QT
5. ST
Solution:
1.
VL
Vf
VL
440 volts
Rev. 0
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