ALTERNATORS

Question 1

1. The main disadvantage of using short-pitch winding in alternators is that it
   A. Reduce harmonics in the generated voltage
   B. Reduce the total voltage around the armature coils
   C. Produces asymmetry in the three phase windings
   D. Increases copper of end connections

Answer 1

B. Reduce the total voltage around the armature coils

Question 2

2. Three phase alternator are invariably wye connected because
   A. Magnetic losses are minimized
   B. Less turns of wire are required
   C. Smaller conductors can be used
   D. Higher terminal voltage obtained

Answer 2

D. Higher terminal voltage obtained

Question 3

3. Two identical alternators are running in parallel and carry equal loads. If excitation of one aternator is increased without changing its steam supply, then
   A. It will keep supplying almost the same load
   B. kVAR supplied by it would decrease
   C. It’s power factor increase
   D. KVA supplied by it would decrease

Answer 3

A. It will keep supplying almost the same load

Question 4

4. Armature reaction in an alternator primarily affects
   A. Rotor speed
   B. Terminal voltage
   C. Frequency
   D. Generated voltage

Answer 4

D. Generated voltage

Question 5

5. As load power factor of an alternator becomes more leading, the value of generated voltage required to give rated terminal voltage
   A. Increase
   B. Remain unchanged
   C Decreases
   D. Varies with rotor speed

Answer 5

C. Decreases

Question 6

6. At leading power factor, the armature flux in an alternator ____ the rotor flux
   A. Opposes
   B. Aids
   C. Distorts
   D. Does jot affect

Answer 6

B. Aids

Question 7

7. The power factor of an alternator is determined by its
   A. Speed
   B. Load
   C. Excitation
   D. Prime mover

Answer 7

B. Load

Question 8

8. For proper parallel operation, alternators must have the same
   A. Speed
   B. Excitation
   C. kVA rating
   D. Voltage rating

Answer 8

D. Voltage rating

Question 9

9. Of the following condition, the one which does not have to be met by alternators working in parallel is
   A. Terminal voltage of each machine
   B. The machines must have the same phase rotation
   C. Thw machines must operate at the same frequency
   D. The machines must have equal ratings

Answer 9

D. The machines must have equal rating

Question 10

10. A 50 Hz alternator will run at the greatest possible speed if it is wound for poles.
    A. 8
    B. 4
    C. 6
    D. 2

Answer 10

D. 2