Design of Electrical Machine 6

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Electrical Engineering MCQ Question Papers: Campus Placement

Subject: Design of Electrical Machine 6

Part 6: List for questions and answers of Design of Electrical Machine

 

Q1. Tap changing facility is generally provided on

a) High voltage transformers

b) Distribution transformers

c) Current transformers

d) Step up transformers

 

Q2. In case of air natural cooling, the cooling surface increases as the __________ of the size

a) Inverse

b) Inverse square

c) Square

d) Cube

 

Q3. In case of air natural cooling the losses increase as the __________ of the size

a) Inverse

b) Inverse square

c) Square

d) Cube

 

Q4. The heat generated in the transformer is dissipated to the surroundings mainly by

a) Conduction

b) Convection

c) Radiation

d) All of the above

 

Q5. The heat transfer by convection least depends on

a) Temperature difference

b) Air velocity

c) Surface area

d) Color of the paint

 

Q6. Oil for transformer cooling should have low

a) Dielectric strength

b) Viscosity

c) Flash point

d) None of these 

 

Q7. Oil for transformer cooling should have high

a) Flash point

b) Viscosity

c) Sludging tendencies

d) Moisture content

 

Q8. The oil selected for transformer cooling should be free from

a) Alkalies

b) Acids

c) Sulphur

d) All of the above

 

Q9. Normally for the design of transformer the ambient temperature is taken as

a) 20 deg. C

b) 25 deg.C

c) 45 deg.C

d) 75 deg.C

 

Q10. A transformer is designed for certain ambient temperature. If it actually operates at a temperature 10 deg.C above the design temperature its kVA rating should be

a) Increased by 10%

b) Reduced by 5%

c) Reduced by 10%

d) Reduced by 20%

 

Q11. The overload capacity of a transformer depends on

a) Ratio of full load copper losses to its iron losses

b) Size of the core

c) Frequency

d) None of the above

 

Q12. Which surge will be most damaging for a transformer ?

a) Steeper front flatter tail

b) Flatter front steeper tail

c) Uniform

d) All will be equally damaging 

 

Q13. A transformer is considered to have a network of series capacitance due to

a) Inter-turn insulation

b) Earthing

c) Laminated core

d) Surrounding tanks

 

Q14. In a transformer the shunt capacitance is decreased and series capacitance is increased by the use of

a) Shielded windings

b) Inter-leaved winding

c) Layer type winding

d) Any of the above

 

Q15. An air core transformer as compared to iron-core transformer has

a) Less magnetic core loss

b) More magnetic core loss

c) No magnetic core loss

d) Less ohmic loss

 

Q16. The ‘hum’ in a transformer is due to

a) Vibrations in cooling oil

b) Vibration in laminations

c) Sinusoidal voltage waveform

d) All of the above

 

Q17. Which test is conducted on transformers to check its ability to withstand the transient voltages due to lightening etc. ?

a) Induced over voltage test

b) Partial discharge test

c) Impulse test

d) Any of the above

 

Q18. The density of transformer oil is around

a) 1.2gm/cc

b) 1 gm/cc

c) 0.95 gm/cc

d) 0.80 gm/cc 

 

Q19. The flash point of transformer oil is usually

a) 50 deg.C

b) 75 deg.C

c) 160 deg.C

d) 150 deg.C

 

Q20. The maximum permissible water content in transformer oil is

a) Zero

b) 10 ppm

c) 25 ppm

d) 50 ppm 

 

Part 6: List for questions and answers of Design of Electrical Machine

 

Q1. Answer: b

 

Q2. Answer: c

 

Q3. Answer: d

 

Q4. Answer: b

 

Q5. Answer: d

 

Q6. Answer: b

 

Q7. Answer: a

 

Q8. Answer: d

 

Q9. Answer: c

 

Q8. Answer: d

 

Q11. Answer: b

 

Q12. Answer: a

 

Q13. Answer: a

 

Q14. Answer: d

 

Q15. Answer: c

 

Q16. Answer: b

 

Q17. Answer: c

 

Q18. Answer:

 

Q19. Answer: d

 

Q20. Answer: d