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GEH-5201, Synchronous-motor Control
SECTION 4 - Description of the CR192 Micro-starting
and Protection Module
ex:
=
Load Angle
<D
Motor At Unity PF
Normal Load lARA
Parallel With Line
Volts
IA
®
Motor PF Swings
Leading When Line
Voltage
Drops And Excitation
Remains
Constant (Due To Fld
Time Const.)
IA
VLine
Motor Does Not Pull
Out PF Approx 1.0
IAXA
_<Dt®
Power
Factor
Lead 0.7
t
0.8
0.9
1.0
1
0.9
0.8
0.7
Lag
0.6
0.5
0 . 4 ' - - - - - - - - - ' - - - - ' - - - - - -
16
@
Motor PF
Becomes Slightly
lARA
Lagging When
Excitation Drop
Equals Line Drop
VLine
~
IA
EG
IAXA
~~g)
@)
Motor PF Dips
A A
Heavily Lagging When
EG - Generated EMF
Line Voltage Is
IA -
Line Amperes
Restored
RA - Armature Resistance
XA -
Arm Reactance
o
0.5
1.0
1.5
Time-Seconds
Figure 18. Motor power factor response
to
line voltage variances
2.0
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