1. Synch. Machine on infinite bus:
Lag Generator
Generator
U.P.F. line
Motor
line of power stability limit
Lead Generator V
EV/ZS
V2/ZS
Lead Motor 
Loci of constant active powers
Lag Motor
Loci of constant EMF

2. Synch. alternator capability curve
Armature heat limit locus Q
Field heat limit locus
U.P.F. line P V Q
V2/xS
Emax V/xs  P
Synch. alternator capability curve

3. & neglecting saturation: Neglecting ra w.r.t. xs
Approximately, at constant active power:
- The EMF phasors represent field currents
- The axs phasors represent armature currents at different power-factors

4. & neglecting saturation Neglecting ra w.r.t. xs
Approximately, at constant active power:
- The EMF phasors represent field currents
- The axs phasors represent armature currents at different power-factors

5. & neglecting saturation Neglecting ra w.r.t. xs
Approximately, at constant active power:
- The EMF phasors represent field currents
- The axs phasors represent armature currents at different power-factors

6. & neglecting saturation: Neglecting ra w.r.t. xs
Approximately, at constant active power:
- The EMF phasors represent field currents
- The axs phasors represent armature currents at different power-factors

7. & neglecting saturation: Neglecting ra w.r.t. xs
Approximately, at constant active power:
- The EMF phasors represent field currents
- The axs phasors represent armature currents at different power-factors

8. & neglecting saturation: Neglecting ra w.r.t. xs
Approximately, at constant active power:
- The EMF phasors represent field currents
- The axs phasors represent armature currents at different power-factors

9. & neglecting saturation: Neglecting ra w.r.t. xs
Approximately, at constant active power:
- The EMF phasors represent field currents
- The axs phasors represent armature currents at different power-factors

10. & neglecting saturation: Neglecting ra w.r.t. xs
Approximately, at constant active power:
- The EMF phasors represent field currents
- The axs phasors represent armature currents at different power-factors

11. & neglecting saturation: Neglecting ra w.r.t. xs
Approximately, at constant active power:
- The EMF phasors represent field currents
- The axs phasors represent armature currents at different power-factors

12. & neglecting saturation: Neglecting ra w.r.t. xs
Approximately, at constant active power:
- The EMF phasors represent field currents
- The axs phasors represent armature currents at different power-factors

13. & neglecting saturation: Neglecting ra w.r.t. xs
P=1 pu
P=0.75 pu
P=0.5 pu
& neglecting saturation: Neglecting ra w.r.t. xs
Approximately, at constant active power:
- The EMF phasors represent field currents
- The axs phasors represent armature currents at different power-factors
&
&
Note: Motor & generator curves are actually different due to the effect of losses an other neglected parameters 13

14. Further Problems
(to be tackled graphically & analytically during tutorials of 28 & 29 December 2015):
1) 3 phase Y alternator has armature resistance and reactance per phase of 0.4 & 6 .
The machine is connected to an infinite bus at 10 kV and delivers 3 MVA at 0.8 lag p.f.,
If the machine is operated at constant active power, and changes in losses are neglected,
find the % change in excitation needed to attain unity power factor operation.
2) 3 phase Y Synch Motor has armature resistance and reactance per phase of 1 & 30 .
The machine is connected to an infinite bus at 11kV and takes 60 A,
Find: Active power intake, EMF for 0.8 lag p.f.,EMF for 0.8 lead p.f.