Design of Electrical Machines Questions and Answers – Pulsation Losses & Types of Leakages

1. What happens in the rotating electrical machine?
a) armatures are slotted
b) armatures are slotted and results in the movement of rotor
c) the rotor remains stationary
d) the rotor slots are rotating

2. What is pulsation losses?
a) flux pulsations are caused due to the slotted armature
b) flux pulsations are caused due to the rotation of machine
c) flux pulsation occurs due to rotor slots are rotating
d) flux pulsations occur due to the change in reluctance

3. In which machine part/parts does the pulsation loss occurs?
a) teeth
b) pole face
c) conductors
d) teeth and pole faces

4. How are the pulsation losses aggravated?
a) if the air gap is small compared with slot openings
b) if the air gap is reduced
c) if the air gap is increased
d) if the air gap is made larger than the slot openings

5. The slotting produces harmonic fields which cause high frequency losses near the gap surface?
a) true
b) false

6. In which machine is the pulsation losses considerable?
a) synchronous motors
b) induction motors
c) dc shunt motors
d) dc series motors

7. What are the factors the permeance depends upon in the zigzag leakage?
a) relative position of stator
b) relative position of rotor
c) relative position of stator and rotor
d) stored energy at any position

8. What is the formula for the stored energy at any position?
a) stored energy at any position = mmf per slot2 * permeance in a particular position
b) stored energy at any position =2 * mmf per slot2 * permeance in a particular position
c) stored energy at any position =1/2 * mmf per slot2 * permeance in a particular position
d) stored energy at any position =1/3 * mmf per slot2 * permeance in a particular position

9. What is the formula for the zigzag permeance?
a) zigzag permeance = average width of the rotor tooth / (1/2 * mmf per slot2)
b) zigzag permeance = average width of the rotor tooth * (1/2 * mmf per slot2)
c) zigzag permeance = 1/average width of the rotor tooth *(1/2 * mmf per slot2)
d) zigzag permeance = average width of the rotor tooth *(1/2 / mmf per slot2)

10. What is the formula of the zigzag specific permeance?
a) zigzag specific permeance = average width of the rotor tooth * length / (1/2 * mmf per slot2)
b) zigzag specific permeance = average width of the rotor tooth / length * (1/2 * mmf per slot2)
c) zigzag specific permeance = average width of the rotor tooth * length * (1/2 * mmf per slot2)
d) zigzag specific permeance =1/ average width of the rotor tooth * length * (1/2 * mmf per slot2)

11. What are the factors the overhang leakage reactance is obtained?
a) length of the overhang
b) diameter of the overhang
c) shape of the overhang
d) length of the overhang along with the shape of the overhang

12. The overhang leakage reactance depends on the degree of the saturation in the ferromagnetic parts?
a) true
b) false

13. What is the relation between the overhang specific permeance and the slot pitch?
a) overhang specific permeance is directly proportional to the slot pitch
b) overhang specific permeance is indirectly proportional to the slot pitch
c) overhang specific permeance is directly proportional to the square of the slot pitch
d) overhang specific permeance is indirectly proportional to the square of the slot pitch

What Is the formula for the amplitude of the fundamental curve?

a) amplitude of the fundamental curve = 1.27 * flux density in the air gap * cosine (phase angle/2)
b) amplitude of the fundamental curve = 1.27 / flux density in the air gap * cosine (phase angle/2)
c) amplitude of the fundamental curve = 1.27 * flux density in the air gap / cosine (phase angle/2)
d) amplitude of the fundamental curve = 1/1.27 * flux density in the air gap * cosine (phase angle/2)

How should the air gap and the fringing effects be if the field form of a salient pole machine is rectangular?

a) air gap under the pole arc is not constant, fringing effects are considered
b) air gap under the pole arc is constant, fringing effects are considered
c) air gap under the pole arc is constant, fringing effects are not considered
d) air gap under the pole arc is not constant, fringing effects are not considered