Electrical Machine 4

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Electrical Engineering MCQ Question Papers: Campus Placement

Subject: Electrical Machine 4

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

 

Q1.The rotational losses in d.c. machines is equal to the

a) Kinetic energy of armature

b) Half of the kinetic energy of armature

c) Square of the kinetic energy of armature

d) Rate of change of kinetic energy

 

Q2.For low reluctance path for the flux in armature, the permeability of the material should be

a) High

b) Low

c) Both (a) and (b)

d) None of these

 

Q3.Differential compound motors are mainly used in

a) Drilling machines

b) Elevators

c) Electric traction

d) Not suitable for any practical application

 

Q4.Which motor is not suitable for the application of centrifugal pumps?

a) Shunt motor

b) Series motor

c) Cumulative compound motor

d) Differential compound motor

 

Q5.A machine operating as motor may go into regenerative braking mode if its speed becomes

a) Sufficiently high to make back emf greater than supply voltage

b) Sufficiently low to make back emf greater than supply voltage

c) Sufficiently high to make back emf half of the supply voltage

d) Sufficiently low to make back emf half of the supply voltage

 

Q6.In the biomedical instruments like artificial heart pumps, the commonly used motor is

a) Permanent magnet d.c. motor

b) Brushless d.c. motor

c) Ward-Leonard system

d) Series motor 

 

Q7.Permanent magnet d.c. motors are extensively used in

a) Automobiles

b) Heaters

c) Air conditioners

d) All of these

 

Q8.The number of windings on the field of permanent magnet d.c. motor is

a) More compared to shunt motor

b) Less compared to shunt motor

c) Absent

d) None of these

 

Q9.The speed of permanent magnet d.c. motor cannot be controlled by

a) Flux control method

b) Rheostatic control method

c) Electronic circuits

d) None of these

 

Q10.The torque constant (Km), of a permanent magnet d.c. motor is 0.25 V sec / radian and armature resistance is 2 ohm. If the applied armature voltage is 90 V, then its zero speed torque is

a) 10.45 N-m

b) 11.25 N-m

c) 13.65 N-m

d) 15.56 N-m

 

Q11.For the protection of d.c. series motor, which starter is commonly used?

a) Two point starter

b) Three point starter

c) Four point starter

d) None of these

 

Q12.Which starter does not provide high speed protection to the d.c. shunt motor?

a) Three point starter

b) Four point starter

c) Two point starter

d) None of these 

 

Q13.The basic difference between three point starter and four point starter is

a) No volt coil is connected in series with the field winding in three point starter while connected independently across the supply in four point starter

b) No volt coil is connected across supply in three point starter while in series with field winding in four point starter

c) No volt coil is connected across field winding in three point starter while connected across supply in four point starter

d) None of these

 

Q14.For frequent starting, stopping and reversals, which motor is commonly used?

a) Permanent d.c. motor

b) Ward-Leonard system

c) Brushless d.c. motor

d) All of these

 

Q15.Ward-Leonard system is used for

a) Wide range of speed control

b) Very sensitive speed control

c) Both (a) and (b)

d) None of these

 

Q16.If a resistance is added in series with the field winding of d.c. shunt motor, then its

a) Both speed and torque decreases

b) Both speed and torque increases

c) Speed decreases, torque increases

d) Speed increases, torque decreases

 

Q17.Which method is suitable for the speed control, below and above the normal rated speed of d.c. shunt motor?

a) Flux control method

b) Rheostatic control method

c) Voltage control method

d) All of these

 

Q18.In armature voltage control method or rheostatic control method for speed control in d.c. shunt motor, a variable resistance is

a) Added in series with the armature

b) Added in series with the field

c) Connected across armature

d) Both in series with armature and field 

 

Q19.In the flux control method for controlling the speed of d.c. shunt motor, the speed control is not possible

a) Below normal rated speed

b) Above normal rated speed

c) Both (a) and (b)

d) None of these

 

Q20.A series wound motor is also called as universal motor because

a) It will run equally well using either an ac or a dc voltage source

b) It will run well below and above rated speed

c) It can be used in all kinds of applications

d) None of these 

 

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

 

Q1. Answer: d

 

Q2. Answer:b

 

Q3. Answer: d

 

Q4. Answer :b

 

Q5. Answer :a

 

Q6. Answer :b

 

Q7. Answer :d

 

Q8. Answer :c

 

Q9. Answer :a

 

Q10. Answer :b

 

Q11.Answer :a

 

Q12. Answer :b

 

Q13. Answer :a

 

Q14. Answer :b

 

Q15. Answer :c

 

Q16. Answer :c

 

Q17. Answer :c

 

Q18. Answer :a

 

Q19. Answer :a

 

Q20. Answer :b