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110
CHAPTER 3 THE SYNCHRONOUS MACHINE
and the value of
Q
now supplied by the generator is
1.0
Q
=
1.7241
[0.80 X 2.0261 cos( 49.9827° ) - 1.0] = 0.0245 per unit
Thus, we sec how excitation controls the reactive power output of the generator.
3.5 LOADING CAPABILI DIAGRAM
All the normal opera ting cond itions 0(" the round-rotor gene rator connected to
an innite bus can be shown on a single diagram, usually called the loadillg
capability diagram or operatioll chart 0(
"
the machine. The cha rt is i mport t to
the power-plant operators who ,Ire resDonsible for proper loading and operalion
of the generator.
The chart is constructed on the assumption that the generator has x ed
terminal voltage
V
, and negligible armature resistance. Construction begins with
the phasor diagram of the machine having