Figure 5.13 Typical form of short-circuit load loss and stray load-loss curves.
(5.39)
(5.40)
§5.5 Steady-State Operating Characteristics
Figure 5.14 Characteristic form of synchronous-generator compounding curves.
Figure 5.15 Capability curves of an 0.85 power factor, 0.80 short-circuit ratio,
hydrogen-cooled turbine generator. Base MVA is rated MVA at 0.5 psig hydrogen.
Figure 5.16 Construction used for the derivation of a synchronous generator capability curve.
(5.41)
(5.42)
(5.43)
Figure 5.17 Typical form of synchronous-generator V curves.
§5.6 Effects of Salient Poles; Introduction to Direct-And
Quadrature-Axis Theory
§5.6.1 Flux and MMF Waves
Figure 5.18 Direct-axis air-gap fluxes in a salient-pole synchronous machine.
(5.44)
(5.45)
(5.45)
Figure 5.19 Quadrature-axis air-gap fluxes in a salient-pole synchronous machine.
Figure 5.20 Phasor diagram of a salient-pole synchronous generator.
§5.6.2 Phasor Diagrams for Salient-Pole Machines
Figure 5.21 Phasor diagram for a synchronous generator showing
the relationship between the voltages and the currents.
(5.46)
(5.47)
Figure 5.22 Relationships between component voltages in a phasor diagram.
(5.48)
(5.49)
(5.50)
5.7 Power-Angle Characteristics Of Salient-Pole Machines
For the purposes of this discussion, it is sufficient to limit our discussion to the simple system shown in the schematic diagram of Fig.5.23a, consisting of a salient pole synchronous machine SM connected to an infinite bus of voltage
through a series impedance of reactance
. Resistance will be neglected because it is usually small. Consider that the synchronous machine is acting as a generator. The phasor diagram is shown by the solid-line phasors in Fig.5.23b. The dashed phasors show the external reactance drop resolved into components due to
and
. The effect of the external impedance is merely to add its reactance to the reactances of the machine; the total values of the reactance between the excitation voltage
and the bus voltage
is therefore
(5.50)
(5.51)
If the bus voltage
is resolved into components its direct-axis component
and quadrature-axis component
in phase with
and
, respectively, the power P delivered to the bus per phase (or in per unit) is
(5.52)
(5.53)
(5.54)
(5.55)
Figure 5.23 Salient-pole synchronous machine and series impedance: (a) single-line diagram and (b) phasor diagram.
Figure 5.24 Power-angle characteristic of a salient-pole synchronous machine showing the fundamental component due to field excitation and the second-harmonic component due to reluctance torque.