Alternator. Part – 1

1. In alternators the standard practice, now a days is to have

A. Rotating field

B. Rotating armature

C. Either of the above

D. None of the above

2. For parallel operation, A.C. polyphase alternators must have the same

A. KVA rating

B. Excitation

C. Speed

D. Voltage rating

3. An alternator is said to be over excited when it is operating at

A. Lagging power factor

B. Unity power factor

C. Leading power factor

D. Any of the these

4. Which one of the following methods would give higher than actual value of regulation of an alternator?

A. ZPF method

B. MMF method

C. EMF method

D. None of the above

5. The hydraulic turbine having rated speed 250 rpm is connected to synchronous generator. In order to produce power at 50Hz, the no. Of pole required in generator are

A. 12

B. 16

C. 6

D. 24

6. The most suitable rotor for a turbo alternator designed to operate at high speed is

A. Salient-pole type rotor

B. Smooth cylindrical type rotor

C. Squirrel cage rotor

D. Either of the above

7. Which of the following method is best for determining the voltage regulation of alternators?

A. EMF method

B. MMF method

C. Potier or zero PF method

D. None of the above

8. The most appropriate operating speeds in rpm of generators used in thermal, nuclear and hydro power plants would respectively by

A. 3000, 3000, 1500

B. 3000, 3000, 300

C. 1500, 1500 and 500

D. 1000, 900 and 750

9. An alternator with frequency (f₁) is to be synchronized with an infinite bus of frequency (f) for proper synchronization

A. f₁ = f

B. f₁ < f

C. f₁ > f

D. either B or C

10. The effect of ______ on main field flux is armature reaction

A. Armature MMF

B. Armature current

C. Armature flux

D. All of the above