148. current with field excitation, at a given output power.

A. a - P; b - Q; c ? T

B. a - Q; b - P; c ? P

C. a - T; b - S; c ? R

D. a - S; b - T; c - U

149. A 50 Hz alternator is rated 500 MVA, 20 kV, with Xd = 1.0 per unit and X"d = 0.2 per unit. It supplies a purely resistive load of 400 MW at 20 kV. The load is connected directly across the generator terminals when a symmetrical fault occurs at the load terminals. The initial rms current in the generator in per unit is

A.7.22

B.6.4

C.3.22

D.2.2

150. A power system has two synchronous generators. The Governor-turbine characterisitics corresponding to the generators are P1 =50 (50 -1), P2 = 100(51 -1) where f denotes the system frequency in Hz, and P1 and P2 are, respectively, the power outputs (in MW) of turbines 1 and 2. Assuming the generators and transmission network to be lossless, the system frequency for a total load of 400 MW is

A. 47.5 Hz

B. 48.0 Hz

C. 48.5 Hz

D. 49.0 Hz

151. A stand alone engine driven Synchronous generator is feeding a partly inductive load. A capacitor is now connected across the load to completely nullify the nductive current. For this operating condition

A. the field current and fuel input have to be reduced

B. the field current and fuel input have to be increased

C. the field current has to be increased and fuel input left unaltered

D. the field current has to be reduced and fuel input left unaltered

152. A capacitor is now connected across the load to completely nullify the nductive current.

A. the field current remains the same but the direction of rotation is forvard

B. the field current remains the same but the direction of rotation is reversed

C. the field current is reversed and the number of poles is doubled

D. the number of poles is doubled without reversing the field current

153. A round rotor generator with internal voltage E1 = 2.0 p.u. and X = 1.1 p.u. is connected to a round rotor synchronous motor with internal voltage E2 = 1.3 p.u. and X = 1.2 p.u. The reactance of the line connecting the generator to the motor is 0.5 p.u. When the generator supplies 0.5 p.u. power, the rotor angle difference between the machines will be

A.57.42

B. 1?

C. 32.58?

D. 122.58?

154. Two 3-phase, Y-connected alternators are to be paralleled to a set of common busbars. The armature has a per phase synchronous reactance of 1.7SI and negligible armature resistance. The line voltage of the first machine is adjusted to 3300V and that of the second machine is adjusted to 3200V. The machine voltages are in phase at the instant they are paralleled. Under this condition, the synchronizing current per phase will be '

A. 16.98A

B.29.41 A

C. 33.96 A

D. 58. 82A

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