SEE 3433 MESIN ELEKTRIK SYNCHRONOUS MACHINES Power and Torque Characteristics

Power and Torque Characteristics +Ef+Ef IaIa jX s RaRa +Vt+Vt Let V t = V t  0 o E f = E f  o Complex power is given by: S = V t I a * = P + jQ This gives : Active powerReactive power

Power and Torque Characteristics S = V t I a * = P + jQ P = Active power = Q = Reactive power = If |Z| = X s hence  = 90 o

Power and Torque Characteristics P, T  90 o P max T max

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