Electrical Machine 9

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Electrical Engineering MCQ Question Papers: Campus Placement

Subject: Electrical Machine 9

Part 3: List for questions and answers of Electrical Machine II

 

Q1. Breather present in a transformer is used to?

a) Absorb atmospheric moisture

b) Prevent insulation failure

c) Cooling

d) All of these

 

Q2.In a transformer sludging is principally due to ?

a) Moisture present in oil

b) Dust particles present inside the tank

c) Decomposition of oil

d) Vaporization of oil

 

Q3.Laminations and varnish are used to reduce the eddy current losses. The laminations and varnish tends to present a?

a) High resistance path to eddy current

b) Low resistance path to eddy current

c) Low reluctance magnetic path

d) High reluctance magnetic path

 

Q4.The hysteresis loss in a transformer is minimized by using ?

a) Laminated sheets of steel

b) Special grade of heat treated grain oriented silicon steel

c) Bracing of transformer assemblies

d) Proper design of winding

 

Q5.For transformers ratings are always given in kVA, not in kW because?

a) It is conventional

b) Power factor of load is not known

c) For higher efficiency

d) To make calculation simple

 

Q6.During starting, the magnetic field produced in a transformer is ?

a) 1.5 times the maximum

b) Equal to the maximum

c) 0.5 times of the maximum

d) Equal to zero 

 

Q7.For a transformer, permeability and hysteresis loss should be ?

a) Low, low

b) Low, high

c) High, low

d) High, high

 

Q8.What happens if dc supply is given to the transformer?

a) Transformer will work more efficiently

b) It will work less efficiently

c) It will work same as with ac supply

d) Not work at all

 

Q9.In a step-up transformer when the voltage delivered is higher than that received, the current delivered is ?

a) Higher than that received

b) Lower than that received

c) Equal to that received

d) Equal to half of that received

 

Q10.The synchronous motor as a synchronous condenser is used to ?

a) Improve power factor

b) Reduce hunting

c) Both (a) and (b)

d) None of these

 

Q11.An over excited synchronous motor operating on no load condition is called as?

a) Synchronous capacitor

b) Synchronous condenser

c) Both (a) and (b)

d) None of these

 

Q12.In a synchronous motor, the phenomenon of hunting caused by the sudden application or removal of load is prevented by ?

a) Using damper winding

b) Using a capacitor

c) Using an inductor

d) All of the above 

 

Q13.Hunting in a synchronous motor results in?

a) Loss of synchronism

b) Mechanical and electrical stresses on motor

c) Large current drawn by motor

d) all of the above

 

Q14.Oscillations of the rotor about its new equilibrium position, due to sudden application or removal of load in synchronous motor is called?

a) Hunting

b) Galloping

c) Swinging

d) Both (a) and (c)

 

Q15.The plot of power factor against the field current of synchronous motor is known as ?

a) V-curves

b) Inverted V-curves

c) Both (a) and (b)

d) None of these

 

Q16.If graph of armature current drawn by synchronous motor is against field current is plotted then the resulted graph is known as?

a) V-curves

b) Inverted V-curves

c) Both (a) and (b)

d) None of these

 

Q17.For critical excitation the power factor of the synchronous motor will be equal to ?

a) 0

b) 1

c) 0.5 M

d) None of the above

 

Q18.If the field of the synchronous motor is overexcited then its power factor will be ?

a) Lagging

b) Leading

c) Unity

d) Zero 

 

Q19.When the excitation of a synchronous motor is changed keeping the load constant then the ?

a) Power factor will change

b) Ia cos Ø remains constant

c) Both (a) and (b)

d) None of these

 

Q20.For a synchronous motor, as the load angle reaches up to 90 ° electrical i.e. half a pole pitch, then the magnetic locking between the stattor and rotor?

a) No longer exis

b) Will be strongest

c) Will be weakest

d) None of these 

 

Part 3: List for questions and answers of Electrical Machine II

 

Q1. Answer: a

 

Q2. Answer: c

 

Q3. Answer: a

 

Q4. Answer: b

 

Q5. Answer: b

 

Q6. Answer: d

 

Q7. Answer: c

 

Q8. Answer: d

 

Q9. Answer: b

 

Q10. Answer: a

 

Q11. Answer: a

 

Q12. Answer: a

 

Q13. Answer: d

 

Q14. Answer: d

 

Q15. Answer: b

 

Q16. Answer: a

 

Q17. Answer: b

 

Q18. Answer: b

 

Q19. Answer: c

 

Q20. Answer: a