Alternators MCQs

A 75 MVA, 10 kV synchronous generator has Xd = 0.4 p.u. The Xd value (in p.u.) to a base of 100 MVA, 11 kV is

current with field excitation, at a given output power.

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

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

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 400V, 50 kVA, 0.8 pf leading A-connected, 50 Hz synchronous machine has a synchronous reactance of 2S1 and negligible armature resistance. The friction and windage losses are 2 kW and the core loss is 0.8 kW. Teh shaft is supplying 9kW load at a power factor os 0.8 leading. The line current drawn is '