TECHNICAL QUIZ-I
EE2403-SPECIAL ELECTRICAL MACHINES
1. The maximum power developed in the synchronous motor will depends on?
A) Rotor excitation supply voltage
B) Power factor
C) Developed torque
D) Rotational speed
2. Synchronous reluctance motor can operate at?
A) Lagging power factor only
B) Leading power factor only
C) Unity power factor only
D) Lagging, leading and unity power factor only
3. When the excitation of an unloaded salient pole synchronous motor gets disconnected
what will happen in the motor?
A) High rates of acceleration
B) Rotor will blast
C) The motor will stop
D) None of these
4. For what purpose the armature of the special machine is laminated?
A) To reduce eddy current loss
B) To avoid shorting
C) To reduce commutation failure
D) Both A and B
5. Power Factor of Synchronous Motor can be varied by varying which of the following
quantity?
A) Supply Frequency
B) Armature current
C) Excitation
D) Applied voltage
6. which one is the type of SYNREL motor?
A) Vernier motor
B) Hybrid motor
C) PM machine
D) None of these
7. A SYNCHRO has
A) a 3-phase winding on rotor & a single phase winding on stator
B) a 3-phase winding on stator & a commutator winding on rotor
C) a 3-phase winding on stator & a single phase winding on rotor
D) a single phase winding on rotor & a commutator winding on stator
8. The high stepping rate of stepper motor…………
A) 10000 steps/sec
B) 20000 steps/sec
C) 22000 steps/sec
D) 12000steps/sec
9. In which mode stepper motors are mostly operated?
A) Open loop
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B) Closed loop
C) Both open & closed loop
D) None of these
In variable reluctance stepper motor the rotor made up of what?
A) Soft iron
B) Composite materials
C) Permanent magnets
D) Magnetic steel
The minimum step angle of stepper motor……..
A) 4.5˚
B) 7.2˚
C) 0.72˚
D) 90˚
In a Synchronous machine, rotor windings are supplied with ____ power supply
A) AC
B) DC
C) Pulses
D) No supply
The speed of synchronous motor will ____ from no load to full load
A) Remains same
B) Decrease
C) Increase
D) constant
What is the main application of synrm?
A) Speed control
B) Voltage control
C) Power control
D) None of these
Which is the classification of synrm?
A) Axially laminated
B) Radialy laminated
C) Both a and b
D) None of these
In shipping applications which motors are preferred?
A) Reluctance motor
B) Stepper motor
C) Synchro
D) Hybrid motor
The name of an electrical stepper motor?
A) Synchoronous machine
B) Induction machine
C) Servomotor
D) None of these
Which of the following is an equivalent of a stepper motor?
A) Variable reluctance motor
B) Vernier motor
C) SYNREL motor
D) Cageless motor
19. In a two phase bipolar stepper motor, how many field coils are placed?
A) 2
B) 8
C) 4
D) 6
20. The maximum torque produced by a stepper motor at stand still is called as?
A) Holding torque
B) Detent torque
C) Pull in torque
D) Pull out torque
21. What happens if supply is given at rotor side in any machine?
A) Short circuit occur
B) Rotor needs variable frequency
C) Machine will blast
D) Rotor will block
22. Which instrument measures the rotations speed of shaft in a motor?
A) Servomotor
B) Tachometer
C) None of these
D) Both a & b
23. Which special type of motor has rotor movements in discrete steps?
A) Stepper motor
B) Reluctance motor
C) Servomotor
D) None of these
24. A salient pole synchronous motor is running at no load. Its field current is switched off.
The motor will
A) come to stop.
B) continue to run at synchronous speed.
C) continue to run at a speed slightly more than the synchronous speed.
D) continue to run at a speed slightly less than the synchronous speed
25. In a stepper motor the angular displacement
A) can be precisely controlled.
B) it cannot be readily interfaced with micro computer based controller.
C) the angular displacement cannot be precisely controlled.
D) it cannot be used for positioning of work tables and tools in NC machines.
26. The generation voltage is usually
A) between 11 KV and 33 KV.
B) between 132 KV and 400 KV.
C) between 400 KV and 700 KV.
D) None of the above.
27. A hysteresis motor
A) is not a self-starting motor.
B) is a constant speed motor.
C) needs dc excitation.
D) can not be run in reverse speed.
28. In a 3-phase synchronous motor
A) the speed of stator MMF is always more than that of rotor MMF.
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B) the speed of stator MMF is always less than that of rotor MMF.
C) the speed of stator MMF is synchronous speed while that of rotor MMF is zero.
D) rotor and stator MMF are stationary with respect to each other.
An a.c. tachometer is just a ________with one phase excited from the carrier frequency.
A) two-phase A.C. servomotor
B) two-phase induction motor
C) A.C. operated universal motor
D) hybrid stepper motor.
A salient pole synchronous motor is running with normal excitation, if the excitation is
reduced to zero ………..
A) the motor would stop
B) it becomes a reluctance motor
C) it becomes an induction motor
D) it remains a synchronous motor
The power factor of a synchronous motor is better than that of induction motor because
…………..
A) synchronous motor runs at synchronous speed
B) Stator supply is relieved of responsibility of producing magnetic field
C) mechanical load on the motor can be adjusted
D) synchronous motor has large air gap
Which of the following is an unexcited single phase synchronous motor?
A) Universal motor
B) AC series motor
C) Repulsion motor
D) Reluctance motor
In which of the following motors the stator and rotor magnetic field rotate at the same
speed?
A) universal motor
B) Synchronous motor
C) Reluctance motor
D) Induction motor
When synchronous motor is pulled out of synchronism, the stator current
………………….
A) is decreased too much
B) becomes zero
C) is increased too much
D) remains unchanged
A synchronous motor develops maximum power when load angle is …………………..
A) 900
B) 600
C)1200
D) 450
In a synchronous motor, the maximum power developed depends on all of the following
except ………..
A) maximum value of coupling angle
B) supply voltage
C) rotor excitation
D) direction of rotation
37. During hunting of synchronous motor ……………….
A) harmonics are developed in the armature circuit
B) Negative phase sequence currents are generated
C) damper bar develops torque
D) field excitation increases
38. An over excited synchronous motor is used for
A) variable speed loads
B) fluctuating loads
C) low torque loads
D) power factor correction
39. If one -phase of a 3-phase synchronous motor is short-circuited, motor
……………………
A) will overheat in spots
B) will refuse to start
C) will not come up to speed
D) will fail to pull into step
40. A synchronous motor working at leading power factor can be used as
………………………
A) phase advancer
B) voltage booster
C) noise generator
D) mechanical synchronizer
41. In a rotating electrical machine with 2 poles on the stator and 4 poles on the rotor,
spaced equally, the net electromagnetic torque developed is ____________
A) maximum
B) zero or no torque is developed
C) minimum
D) none of the mentioned
42. For the development of electromagnetic torque in a rotating electrical machine, the
number of rotor poles must be ____________
A) greater than the stator poles
B) less than the stator poles
C) equal to the stator poles
D) either greater or lesser than the stator poles
43. Torque angle ‘δ’ is the angle between ____________
A) rotor field axis and resultant field axis
B) stator field axis and rotor field axis
C) stator field axis and mutual field axis
D) stator field axis and resultant field axis
44. The basic torque and EMF expression of rotating electrical machines are ____________
A) applicable to DC machines only
B) applicable to AC machines only
C) applicable to both AC and DC machines
D) none of the mentioned
45. The final forms of the expression for generated EMF and torque, for AC and DC
machines differ, because ____________
A) the fundamental principles underlying their operation are same
B) the fundamental principles underlying their operation are different
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C) their construction details are same
D) their construction details are different
The disadvantage of cylindrical winding is
A) increased eddy current loss
B) high copper loss
C) low mechanical strength
D) all of the above.
The EMF produced in dc generator is ___ induced EMF
A) Statically
B) Electro statically
C) Magnetically
D) Dynamically
If the flux of the dc motor attains zero, its speed will become
A) Zero
B) Full load speed
C) Synchronous speed
D) Infinite
Which of the following DC Motor is employed in high traction applications
A) DC Compound Motor
B) DC Shunt Motor
C) DC Series Motor
D) DC Differential Compound Motor
The function of ____ in dc generator is to collect current from commutator and deliver
it to external circuit
A) Brushes
B) Equalizer rings
C) End rings
D) Dummy Coils
The Current flowing through the armature of the dc motor is
A) AC
B) None of the Answers
C) DC
D) Pulsating
The rotating part of the dc machine is known as
A) Stator
B) Rotor
C) Armature
D) Field
The main advantage of dc motors compared to ac motors are
A) Less Maintenance
B) High Starting Torque
C) Speed Control
D) Low Cost
Starter is used in DC Motor for which of the following purpose
A) Improve efficiency
B) Reduce Starting Current
C) Improving Back EMF
D) Improving Starting Torque
55. The power rating that is indicated on name plate of any motor is
A) Gross Power
B) Output Power of Shaft
C) Power drawn in KVA
D) Net Power
1. A
29. D
2. D
30. B
3. C
31. B
4. A
32. D
5. C
33. B
6. A
34. C
7. C
35. A
8. B
36. D
9. A
37. C
10. A
38. D
11. C
39. B
12. B
40. A
13. A
41. B
14. A
42. C
15. C
43. B
16. C
44. C
17. A
45. D
18. A
46. C
19. C
47. D
20. A
48. D
21. C
49. C
22. B
50. A
23. A
51. A
24. B
52. C
25. A
53. B
26. A
54. B
27. B
55. B
28. D