Design of Electrical Machine 4

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Electrical Engineering MCQ Question Papers: Campus Placement

Subject: Design of Electrical Machine 4

Part 4: List for questions and answers of Design of Electrical Machine


Q1. The percentage of overload on a continuous rating machine is

a) zero

b) 5%

c) 10%

d) 50%


Q2. Open circuit test on a transformer is conducted to obtain

a) The leakage impedances

b) The ohmic loss

c) Hysteresis loss only

d) Core loss only


Q3. Heat transfer capability of hydrogen is nearly __________ times that of air

a) 2

b) 3

c) 7

d) 17


Q4. The density of hydrogen is __________ that of air

a) 14

b) 1/4

c) 1/7

d) 1/14


Q5. Turbo-alternators of rating __________ and above are normally hydrogen cooled

a) 10 MW

b) 20 MW

c) 25 MW

d) 50 MW


Q6. Iron losses of a machine are

a) Directly proportional to flux density

b) Directly proportional to the square of flux density

c) Inversely proportional to flux density

d) Inversely proportional to the square of flux density 


Q7. While considering hysteresis loss in a transformer, under which of the following the loss will not increase ?

a) When flux density is increased by 10%

b) When thickness of lamination is caused by 10%

c) When frequency is increased by 10%

d) When both thickness and frequency are increased by 10%


Q8. The shaft of electric motors is generally made of

a) Mild steel

b) Cast iron

c) Copper

d) Aluminium alloy


Q9. The critical speed of the shaft for an electric motor should be

a) Away from the operating speed

b) Exactly the same as operating speed

c) Half the operating speed

d) Double of the operating speed


Q10. The shaft of electric motors is generally supported in

a) Magnetic bearings

b) Bush bearings

c) Ball or roller bearings

d) Cast iron bearings


Q11. Ball and roller bearings are generally lubricated by

a) Graphite

b) Grease

c) Water

d) Air


Q12. In case of ball bearings, the ball are made of

a) Cast iron

b) Mild steel

c) Carbon chrome steel

d) None of the above 


Q13. A ball bearing is secured to the shaft by means of

a) Key

b) Slot

c) Pin

d) Sleeve


Q14. In case of 110 MW generators, the shaft is supported on

a) Ball bearings

b) Roller bearing

c) Needle bearings

d) Bush bearings


Q15. Which of the following is classed as anti frictionbearing ?

a) Ball bearing

b) Roller bearing

c) Needle bearing

d) All of the above


Q16. The force exerted by a lifting magnet varies with distance (D) as

a) D

b) D^2

c) 1/D

d) 1/D^2


Q17. Transformer-core laminations are made of

a) Cast iron

b) Wrought iron

c) Silicon steel

d) Cast steel


Q18. When commutation is obtained by increasing the current density at the leading edge and decreasing the same at trailing edge, it is known as

a) Under commutation

b) Over commutation

c) Straight commutation

d) Sinusoidal commutation 


Q19. Skewing in the slots of an induction motor is provided to reduce

a) iron loss

b) noise

c) harmonics

d) temperature rise


Q20. Sometimes a reactor is connected in series with a transformer to

a) improve regulation

b) control fault current

c) improve efficiency

d) improve power factor 


Part 4: List for questions and answers of Design of Electrical Machine


Q1. Answer: c


Q2. Answer: d


Q3. Answer: c


Q4. Answer: d


Q5. Answer: d


Q6. Answer: a


Q7. Answer: b


Q8. Answer: a


Q9. Answer: a


Q10. Answer: c


Q11. Answer: b


Q12. Answer: c


Q13. Answer: d


Q14. Answer: d


Q15. Answer: d


Q16. Answer: d


Q17. Answer: c


Q18. Answer: b


Q19. Answer: c


Q20. Answer: b