Electrical Machine Design MCQ PDF Download

1. The major consideration(s) to evolve a good design is/are

(a) durability.
(b) cost.
(c) compliance with performance criteria as laid down in specifications.
(d) all of the above.

2. The main areas of design are

(a) magnetic circuit.
(b) electrical circuit.
(c) insulation.
(d) thermal circuit.
(e) mechanical construction.
(f) all of the above.

3. Limitation(s) imposed on the design is /are

(a) saturation of magnetic parts.
(b) temperature rise.
(c) efficiency.
(d) power factor.
(e) commutation.
(f) all of these.

4. Power factor imposes a limitation on motors.

(a) dc
(b) synchronous
(c) induction
(d) none of these

5. Commutation imposes limitation on

(a) induction motors.
(b) dc motors.
(c) synchronous motors.
(d) all of these.

6. The design of mechanical parts is particularly important in case of ……… speed machines.

(a) high
(b) medium
(c) low
(d) all of these.

7. The action of electromagnetic machines is based upon the principle(s) of

(a) induction.
(b) interaction.
(c) alignment.
(d) all of these.

8. The basic needs of a good conducting material used for windings of electrical machines are

(a) highest possible conductivity and least possible temperature coefficient of resistance.
(b) high tensile strength and absence of brittleness.
(c) reliability, durability, good weldability and solderability.
(d) all of the above.

9.……… is universally used for windings of electrical machines.

(a) Silver
(b) Aluminium
(c) Hard drawn copper
(d) Annealed copper

10. Aluminium when used as a conductor material in………. transformer reduces the overall cost of the transformer.

(a) large size
(b) medium size
(c) small size
(d) any size of

11. Aluminium when used as a conductor material in large size transformer, it

(a) gives reduced overall cost.
(b) gives increased size and cost.
(c) does not affect the size and cost.

12. It is difficult to substitute aluminium for copper for windings of electrical machines. This is due to its

(a) much lower tensile strength.
(b) higher resistivity.
(c) both (a) and (b).
(d) none of these.

13. ………is used in the manufacture of resistance grids for the motor starters.

(a) Cast iron
(b) Copper
(c) Aluminium
(d) Steel

14. The desired properties of magnetic materials used for electrical machines are

(a) narrow hysteresis loop to give small hysteresis loss.
(b) increased resistivity to give small eddy current loss.
(c) free from ageing problem.
(d) high ductility and free from brittleness.
(e) high permeability and high saturation flux density.
(f) all of the above.

15. For a soft magnetic material there will be

(a) steeply rising magnetization curve.
(b) relatively narrow and small hysteresis loop.
(c) less energy loss per cycle of magnetization.
(d) all the above.

16. For a given frequency and maximum flux density, the hysteresis loss in ‘soft’ magnetic material is ……… in hard magnetic material.

(a) more than that
(b) less than that
(c) the same as that

17. Hot rolled sheets have ………… permeability.

(a) zero
(b) low
(c) unity
(d) high

18. Addition of silicon in iron laminations

(a) almost eliminates the ageing problem.
(b) increases the electrical resistivity of iron thereby reduces the eddy current loss.
(c) reduces hysteresis loss.
(d) increases the permeability at low and moderate flux densities but decreases it at high flux densities.
(e) all of the above.

19. Silicon content in iron laminations is kept within 5% as it

(a) increases hysteresis loss.
(b) increases cost.
(c) makes the material brittle.
(d) reduces the curie point.

20. Unbalanced magnetic pull is proportional

(a) directly with d.
(b) inversely with d.
(c) directly with d².
(d) inversely with d².