Slide 1
Electric Machinery BProf. Dr. Juan Segundo Ramrez
Synchronous Machine ModelLecture #1Lesson 1 IntroductionLesson
summaryIntroductionSynchronous machine types Round rotor machine
modelEquivalent circuit Synchronous gen. capability curve
Instructional objective On completion of this lesson a student
should be able to:Explain the applications of synch. M in a power
systemDevelop the Eq. Circuit model of a round rotor Synch
MachineExplain the Operating Characteristics of a synch.
GeneratorTHE SYNCHRONOUS MACHINEWhere f=electrical frequency in Hz
P=number of poles N=rotor speed in revolutions per minute (rpm)
fm=N/60, the mechanical frequency in revolutions per second
(rps)
Elementary three-phase ac generator showing end view of the
two-pole cylindrical rotor and cross section of statorstator
Cross section of an elementary stator and salient-pole
rotor.
Steady State OperationSteady State Operation
ibva21
Real and Reactive Power Control
Equating real and imaginary quantities in this equation, we
obtain
The dependence of P on the power angle is also shows as follows
if
Where and , are expressed in volts to neutral or in per unit,
then
Therefore, the complex power delivered to the system at the
terminals of the generator is given by
a-axis
Direct axis
Rotation
Rotating field
fc-axis
c
Quadrature axis
ab
a
bc
Similar results are found for phase b and c
Generated Due to armature At no load resistance
Due to armature Due to armature Self-reactance mutual
reactance
ZdZdEquivalent circuits for (a) the synchronousGenerator and (b)
the synchronous motor withConstant synchronous impedance
a)b)
b)
a)
Phasor diagrams of: (a) overrexcited generator delivering
lagging current (b) underexcited motor drawing lagging current
.
and
and
Phasor diagrams showing constant-power loci of an (a)
overexcited generator delivering reactive power to the system; (b)
underexcited generator recciving reative power from system. The
power delivered by the generator is the same in both cases.
Constant power Locus of
Constant powerLocus of a)b)0
