Design of Electrical Machine 5

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Electrical Engineering MCQ Question Papers: Campus Placement

Subject: Design of Electrical Machine 5

Part 5: List for questions and answers of Design of Electrical Machine

 

Q1. Skewing of rotor slots helps in

a) Improving beat transfer

b) Reducing noise

c) Suppressing undesirable harmonics

d) All of the above

 

Q2. The harmonics in rotating machines are generated due to

a) Non-sinusoidal field form

b) Slotting of the stator core

c) Both (A) and (B) above

d) None of the above

 

Q3. The effect of harmonics in rotating machines can be minimized by

a) Use of longer air gap

b) Skewing the poles

c) Use of distributed winding

d) All of the above

 

Q4. Which of the following measure will not help in reducing the effect of harmonics ?

a) Connecting 3 phase winding in star or delta without neutral

b) Use of short pitch coils or fractional slot windings

c) Chamfering the pole shoes of salient pole machines

d) Reducing the number of slots per pole per phase

 

Q5. In dc machines the number of poles is generally decided by

a) Frequency of flux reversals

b) Weight of iron parts

c) Weight of copper

d) All of the above

 

Q6. In dc machines by increasing the number of poles, all of the following reduce except:

a) Weight of copper

b) Weight of iron parts

c) Frequency of flux reversals

d) Overall size of the machine 

 

Q7. Transformer action requires a

a) Constant magnetic flux

b) Increasing magnetic flux

c) Alternating magnetic flux

d) Alternating electric flux

 

Q8. Which component of the no load current of the transformer is opposite in phase to the

induced emf ?

a) Magnetizing component

b) Core loss component

c) Both (A) and (B) above

d) None of the above

 

Q9. In transformers, the cylindrical winding with rectangular conductors is generally used

for

a) Low voltage winding

b) High voltage winding

c) Tertiary voltage winding

d) Any of the above

 

Q10. Cylindrical winding on transformers is generally not used beyond

a) 6 kV

b) 30 kV

c) 66 kV

d) 132 kV

 

Q11. The disadvantage of cylindrical winding is

a) Increased eddy current loss

b) High copper loss

c) Low mechanical strength

d) All of the above

 

Q12. For transformer laminations

a) Hot rolled silicon steel is preferred

b) Cold rolled silicon steel is preferred

c) Grain oriented silicon steel is preferred

d) Any of the above steel can be used 

 

Q13.The percentage of silicon in the core steel is

a) 1 to 2 percent

b) 2 to 3 percent

c) 4 to 6 percent

d) 8 to 10 percent

 

Q14. The stacking factor will be least for

a) Square core

b) Cruciform core

c) Three stepped core

d) Four stepped core

 

Q15.In static transformers mechanical forces are produced due to

a) vibrations

b) Gap between laminations

c) Interaction of current flowing in the conductor and leakage flux around it

d) None of the above

 

Q16.The thickness of laminations of the core of a power transformer usually

a) 0.003 to 0.05 mm

b) 0.03 to 0.05 mm

c) 0.03 to 0.5 mm

d) 3 to 5 mm

 

Q17. Transformer action requires a

a) Short circuiting

b) Increasing resistivity

c) Reducing resistivity

d) All of the above

 

Q18. In an oil filled transformer, oil is provided for

a) Cooling

b) Insulation

c) Lubricating

d) Both cooling and insulation

 

Q19. The dimensions of a dc machine primarily depend on

a) kW output

b) Work done per revolution

c) Exposed surface

d) None of the above 

 

Q20. The diameter of a 10 SWG wire will be closer to

a) 2mm

b) 1mm

c) 3 mm

d) 13 mm 

 

Part 5: List for questions and answers of Design of Electrical Machine

 

Q1. Answer: c

 

Q2. Answer: c

 

Q3. Answer: d

 

Q4. Answer: d

 

Q5. Answer: d

 

Q6. Answer: c

 

Q7. Answer: b

 

Q8. Answer: b

 

Q9. Answer: a

 

Q10. Answer: a

 

Q11. Answer: c

 

Q12. Answer: d

 

Q13. Answer: c

 

Q14. Answer: a

 

Q15. Answer: c

 

Q16. Answer: c

 

Q17. Answer: c

 

Q18. Answer: d

 

Q19. Answer: b

 

Q20. Answer: c