Design of Electrical Machines Practice Test 5

1. What is the relation between coil span and harmonics?

low coil span decreases the harmonics drastically

low coil span decreases harmonics to less amount

high coil span decreases the harmonics drastically

high coil span decreases the harmonics by small amount

2. When is the range of the number of slots per pole per phase in the salient pole machines?

2-3

2-6

2-4

3-4

3. What is the range of the pressure under which the field coils are consolidated?

4-10 MN per m²

4-12 MN per m²

3-10 MN per m²

4-15 MN per m²

4. The overhang has to be highly reinforced in turbo alternators.

false

true

5. The coil span should be 8.33 percent of pole pitch to obtain the maximum reduction of harmonics.

true

false

6. What is the range of the pole face loss in the synchronous machines?

40-60 % of iron loss

25-70 % of iron loss

40-80 % of iron loss

20-60 % of iron loss

7. What is the formula of the resistance of the winding is calculated at 75°C?

resistance of the winding = (Number of field turns * pole proportion / length of mean turns of the coil) / area of the field conductors

resistance of the winding = (Number of field turns / pole proportion * length of mean turns of the coil) / area of the field conductors

resistance of the winding = (Number of field turns * pole proportion * length of mean turns of the coil) / area of the field conductors

resistance of the winding = (Number of field turns * pole proportion * length of mean turns of the coil) * area of the field conductors

8. What are the factors the pole face loss depends upon?

slot opening, air gap length, number of slots and speed of machines

air gap length

slot opening

number of slots and speed of machines

9. What is the classification of the iron loss due to the main field?

hysteresis loss and eddy current loss

eddy current loss

hysteresis loss

hysteresis loss or eddy current loss

10. During the pressing and consolidation by how much is the thickness of the interturn insulation reduced to?

0.36 mm to 0.25 mm

0.36 mm to 0.26 mm

0.32 mm to 0.25 mm

0.30 mm to 0.25 mm