Design of Electrical Machines Practice Test 2

1. What is the formula for frequency of flux reversals?

f = (p*n)/2

f = n/p

f = p*n

f = p/n

2. What is the relationship between utilization factor and the number of core steps?

utilization factor is indirectly proportional to the square of number of core steps

utilization factor is directly proportional to the square of number of core steps

utilization factor is directly proportional to the number of core steps

utilization factor is indirectly proportional to the number of core steps

3. What is the formula for the area of the poles shrank of the laminated poles?

area of the pole shrank = flux in the pole body - magnetic field

area of the pole shrank = flux in the pole body + magnetic field

area of the pole shrank = flux in the pole body / magnetic field

area of the pole shrank = flux in the pole body * magnetic field

4. What is the meaning of useful flux?

the flux that is wasted

the flux which can be used

the flux which is being created in the machine

the flux which can produce the output

5. What type of heat dissipation takes place when heat flows from the walls of the cooler to the cooling medium?

radiation

conduction and radiation

convection

convection and radiation

6. How should the field mmf be with respect to armature mmf to reduce the armature reaction?

armature mmf >= field mmf

armature mmf < field mmf

armature mmf > field mmf

armature mmf = field mmf

7. What happens to the length of the commutators with the increase in number of poles?

The length of commutators are increased

The length of commutators are decreased

The length of commutators are stable

The length of commutators are higher

8. What is the formula for the window space factor, when the output is 1000 kVA?

12 / (30+kV)

10 / (30+kV)

11 / (30+kV)

9 / (30+kV)

9. What is stacking factor?

the allowance made for the heat loss between laminations

the allowance made for the space loss between laminations

the allowance made for the power loss between laminations

the allowance made for the power loss

10. What does the window space factor depend on?

it depends on the core

it depends on the armature

it depends on the insulation

it depends on the insulation and copper