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CHAPTER 11
Balanced Three - Phase Circuits
CHAPTER CONTENTS
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11.1 Balanced Three-Phase Voltages
11.2 Three-Phase Voltage Sources
11.3 Analysis of the Wye-Wye Circuit
11.4 Analysis of the Wye-Delta Circuit
11.5 Power Calculations in Balanced ThreePhase Circuits
11.6 Measuring Average Power in ThreePhase Circuits
11.1 Balanced Three-Phase Voltages
(a)
(b)
Phasor diagrams of a balanced set of threephase voltages. (a) The abc (positive)
sequence. (b) The acb (negative) sequence.
11.2 Three-Phase Voltage Sources
The two basic
connections of an
ideal three-phase
source.
(a) A Y-connected
source.
(b) A ∆-connected
source
A model of a three-phase source with winding
impedance:
(a) A Y-connected source.
(b) A ∆-connected source
11.3 Analysis of the Wye-Wye Circuit
A three-phase Y-Y system
Phasor diagrams
showing the
relationship
between line-toline and line-toneutral voltages
in a balanced
system.
(a)The abc
sequence.
(b)The acb
sequence.
11.4 Analysis of the Wye-Delta
Circuit
A circuit used to establish the relationship between
line currents and phase currents in a balanced ∆
load.
Phasor diagrams
showing the
relationship
between line
currents and
phase currents
in a ∆connected load.
(a)The positive
sequence.
(b)The negative
sequence.
11.5 Power Calculations in Balanced
Three-Phase Circuits
TOTAL REAL POWER IN A
BALANCED THREE-PHASE
LOAD
TOTAL REACTIVE
POWER IN A BALANCED
THREE-PHASE LOAD
TOTAL COMPLEX POWER
IN A BALANCED THREEPHASE LOAD
11.6 Measuring Average Power in
Three-Phase Circuits
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A wattmeter measures
the average power
delivered to a load by
using a current coil
connected in series
with the load and a
potential coil
connected in parallel
with the load.
A circuit used to analyze the two-wattmeter
method of measuring average power
delivered to a balanced load.
THE END