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electrical machine design MCQs

Practise focused electrical machine design questions with marked answers for exam preparation and subject revision.

electrical machine design Mcqs
1. A current density of __________ is ilsed for large power transformers with forced circulation of oil or with water cooling coils?
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A. 1.5 to 2.5 A/mm2

B. 4.0 to 5.0 A/mm2

C. 5.4 to 6.2 A/mm2

D. 3.5 to 4.5 A/mm2

2. In D.C. machines the width of the duct is usually_____________?
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A. 6 mm

B. 4 mm

C. 8 mm

D. 10 mm
3. ____________are always double layer type?
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A. Open windings

B. Closed windings

C. Either of the above

D. None of the above

4. If an insulating material is operated beyond the maximum allowable temperature, its life is_____________?
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A. unaffected

B. drastically increased

C. none of the above

D. drastically reduced
5. In a D.C. machine the number of brush arms is _________ the number of poles?
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A. less than

B. none of the above

C. equal to

D. greater than

6. The design of electromagnets is based upon which of the following fundamental equations ?
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A. Force equation

B. Voltage equation

C. All of the above

D. Magnetic circuit equation

E. Heating equation

7. D.C. machines designed with a large value of air gap length have_____________?
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A. worst, ventilation

B. none of the above

C. poor ventilation

D. better ventilation
8. impose limitation on design____________?
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A. Power factor

B. Efficiency

C. All above

D. Saturation

E. Temperature rise

9. The action of electromagnetic machines can be related to which of the following basic principles __________?
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A. Induction

B. Interaction

C. Alignment

D. All of the above
10. Direct water cooling of rotor winding presents_____________?
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A. none of the above

B. lesser mechanical difficulties

C. no mechanical difficulties

D. greater mechanical difficulties
11. When the two coil sides forming a coil are spaced exactly one pole pitch apart they are said to be of_____________?
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A. full pitch

B. none of the above

C. either of the above

D. short pitch

12. The length cf air gap to be provided in __________ is primarily determined by power factor consideration?
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A. d.c. shunt motor

B. induction motor

C. d.c. series motor .

D. synchronous motor

13. Hot rolled sheets have ___________ value of permeability?
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A. low

B. zero

C. none of the above

D. high

14. The insulation between windings and grounded core and the insulation between the windings of the same phase is called__________________?
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A. minor insulation

B. either of the above

C. none of the above

D. major insulation
15. In _________ machines, the size of the shaft is decided by the critical speed which depends on the deflection of the shaft?
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A. medium

B. any of the above.

C. small

D. large
16. With direct water cooling it is possible to have ratings of about_____________?
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A. 300 MW

B. 400 MW

C. 600 MW

D. 200 MW

17. The input impedance of a JFET is _____________that of an ordinary transistor?
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A. less than

B. more than

C. none of the above

D. equal to

18. __________is extensively used for those portions of magnetic circuit which carry steady flux and need superior mechanical properties ?
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A. Grey cast-iron

B. Stainless steel

C. High carbon steel

D. Cast steel
19. A practical formula for determining the thickness of insulation between low voltage and high voltage windings is__________________?
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A. 1 + 0.2 kVmm

B. 5 + 0.9 kV mm

C. 2 + 0.5 kVmm

D. 4 + 0.7 kV mm

20. Which of the following in an application of D.C. motors?
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A. Battery driven vehicles

B. All of the above

C. Traction

D. Automatic control

E. Drives for process industry