1. SYNCHRONOUS MACHINES Power and Torque Characteristics
SEE 3433
MESIN ELEKTRIK
SYNCHRONOUS MACHINES Power and Torque Characteristics

2. Power and Torque Characteristics+ Ef  Ia
jXs Ra Vt
Let Vt = Vt 0o
Ef = Ef o
This gives :
Complex power is given by:
S = Vt Ia* = P + jQ
Active power
Reactive power

3. Power and Torque Characteristics
P = Active power =
Q = Reactive power =
S = Vt Ia* = P + jQ
If |Z| = Xs hence  = 90o

4. Power and Torque Characteristics
P, T
Pmax
90o
Tmax 

5. Power and Torque Characteristics
The machine will loose synchronism when the power angle,  greater than 90o
P, T 
90o
Pmax
Tmax
e.g. generator operation. As prime mover power increased, generator need to produce torque to ‘pull’ machine to synchronism – limit when =90o
The Tmax or Pmax can be increased by increasing the field excitation