Question

Consider two equal non sallent pole three phase 60 cycle
Y connected 6600 volt 10000-kva synchronous generators, each wuth an effective resistance of 0.063 ohm per phase and a synchronous reactance of 1.52 ohm per phase. Assume that the resistances and reactances of the generators are constant. These generators in parallel carry an inductive load of 18000 kva at 0.9 power factor. (a) find the excitation voltages of the generators and their power angles when they share the kw load equally and operate at the same power factor. (b0 assume that the power laod on generator a is increased by adjusting the gpbernors on the prime movers, keeping the frequency the same, until generator a carries two thirds of the load on the system. The excitation of generator a is kept constant, but the excitation of generator B is adjusted to keep the terminal voltage of the system 6000 volts. Under these new conditions find the excitation voltage of generator B and the new power angles.

Answer 1

Answer:-

given that:

Two equal non-salient 3 phase 60HZ, Y-connected

Load:- 18000 KVA at 0.9 PF lagging.

a) when the two generator share's equal load

generator power

Armature Current

  

  

Phasor Armature current

Negative sign due to lagging PF.

a) Excitation Voltage

Phase value

Line value

From the above phasor voltage

Power Angle

Note:- All the value is calculated in this condition are same for both generator A& B.

b) Load on generator A is increase to 2/3 of rated load.

-excitation voltage kept constant.

  -generator B terminal voltage 6600v

Power delivered by generator B during above condition

at same PF that is 0.9 lagging

Armature current of generator(B)

  

Ampere/phase

New excitation voltage ()

New excitation voltage of generator B

Line voltage of generator B

Power angle