ELECTRICIAN 2nd YEAR MODULE – AC. Three Phase Motor SET 02 ONLINE TEST

Question 1 of 37

1. 63. Where the panel boards are used?

Industrial motor drives

Load distribution for AC & DC supply

Domestic wiring circuits

3 phase domestic wiring

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Question 2 of 37

2. 78. What is the effect on 3 phase induction motor if one phase is cut-off during running with load?

Motor will run normally

Motor will run slow speed but winding will be burnt out shortly

Motor stops at once

Motor runs with humming noise with slow speed

Question 2 of 37

Question 3 of 37

3. 79. What is the defect, if starter with single phasing preventer does not switch ‘ON’?

Improper phase sequence

Loose contact in supply lines

Fluctuations in line voltage

Wrong terminal connections at motor

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Question 4 of 37

4. 80. What is the defect in AC 3 phase induction motor runs at low speed if loaded?

Open circuit in rotor winding

Wrong motor connection

Wrong starter connection

Partially shorted stator winding

Question 4 of 37

Question 5 of 37

5. 60. Which type of winding wire is used to wind submersible pump motors?

Terylene thread type

PVC covered type

Double cotton covered type

Super enamelled type

Question 5 of 37

Question 6 of 37

6. 67. Which method of speed control is only applicable for 3 phase slipring induction motor?

Changing the applied frequency method

Changing the number of stator poles method

Cascade operation method

Rotor rheostat speed control

Question 6 of 37

Question 7 of 37

7. 64. Determine the torque in newton metres produced by a 7.5 HP squirrel cage motor rotating at 1440 rpm?

36.6 Nm

21.63 Nm

24.4 Nm

33.05 Nm

Question 7 of 37

Question 8 of 37

8. 75. Why external resistance is included in the rotor circuit at starting through 3 phase slipring induction motor starter?

To get high starting torque

To reduce the load current

To get high running torque

To get increased speed at starting

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Question 9 of 37

9. 58. Which type of starter is used to start and run the 3 phase slip ring induction motor?

Rotor rheostat starter

Manual star-delta starter

Auto transformer starter

Direct on-line starter

Question 9 of 37

Question 10 of 37

10. 68. What is the name of the winding?

Skew winding

Skein winding

Diamond coil winding

Involute coil winding

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Question 11 of 37

11. 62. Which type of winding has more space for cooling?

Between overhanging coil and wedge

Between overhanging coils and yoke

Between overhanging coils

Between overhanging coil and rotor

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Question 12 of 37

12. 73. Which type of AC motor winding having the number of coil/pole/phase is more than one arranged in different slots?

Basket winding

Distributed winding

Concentrated winding

Concentric winding

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Question 13 of 37

13. 77. What happens to a 3 phase induction motor if one phase fails during running?

Motor stop instantaneously

Motor runs normally

Motor runs with irregular speed

Motor runs slowly, finally it burns

Question 13 of 37

Question 14 of 37

14. 59. What is the function of collar?

 

Helps tightening material for flange

Provides insulation for heat transfer from coil

Provides insulation for coil tapping

Provides insulation around field

Question 14 of 37

Question 15 of 37

15. 81. Which fault condition thermal overload relay protects A.C induction motor?

Under voltage

Open circuit

Over current

Short circuit

Question 15 of 37

Question 16 of 37

16. 87. What indication denotes the shorted coil defect in 3 phase motor stator winding while testing with internal growler by keeping hacksaw blade?

Attracted by the winding turns on the slot

Hacksaw blade gets over heated

Hacksaw blade repels against the slots

Rapid vibration of hacksaw blade

Question 16 of 37

Question 17 of 37

17. 61. What is the reason long chord winding is avoided in AC motors?

Low starting torque

Less heat dissipation

More winding wire required

Low efficiency

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Question 18 of 37

18. 51. Which is the main property of leatheroid paper insulation?

Better ageing and dielectric strength

Non moisturized material

Very good for class F insulation

Highly non-hygroscopic

Question 18 of 37

Question 19 of 37

19. 76. What is the effect of motor, if the rotor windings in slipring induction motor is open circuited at starting?

Will not run

Runs at slow speed

Runs but not able to pull load

Runs at very high speed

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Question 20 of 37

20. 82. What happens to the rotor of a 3 phase induction motor if its speed attains to synchronous speed?

Rotor speed remains same

Rotor speed reduces

Rotor speed increases

Rotor bars get damaged

Question 20 of 37

Question 21 of 37

21. 57. What is the type of rewinding process?

Former winding

Machine winding

Hand winding

Skein winding

Question 21 of 37

Question 22 of 37

22. 86. Which is the cause for the 3 phase motor starter with single phase preventer trips frequently?

Incorrect settings of OLR

Incorrect fuse ratings

Unbalanced line voltage

Improper phase sequence

Question 22 of 37

Question 23 of 37

23. 65. Which type of handle design of rotary switch is illustrated?

Knob

Lever

Key operation

Coin slot

Question 23 of 37

Question 24 of 37

24. 72. Calculate the phase displacement in terms of slots for a 3 phase, 36 slots, 12 coils, 4 pole stator winding?

6 slots

8 slots

4 slots

3 slots

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Question 25 of 37

25. 70. Which is the demerit of 3 phase concentric winding?

More space is required

A stepped former is required

More difficult to shape the coils uniformly

It is not easy to make the end connection

Question 25 of 37

Question 26 of 37

26. 55. Which type of AC winding has the number of coil/pole/phase more than one at different pitches?

Involute coil winding

Flat loop over lapped winding

Diamond coil winding

Flat loop non-over lapped winding

Question 26 of 37

Question 27 of 37

27. 66. What is the purpose of using rotor resistance starter to start 3 phase slip ring induction motor?

Reduce rotor voltage

Increase the torque

Reduce the power loss

Reduce rotor current

Question 27 of 37

Question 28 of 37

28. 74. Which type of testing of winding is illustrated?

Resistance test

Polarity test

Short circuit test

Voltage drop test

Question 28 of 37

Question 29 of 37

29. 85. What happens to a 3 phase induction motor, if one phase fails during starting?

Motor continues to run with irregular speed

Motor runs in slow speed continuously

Motor runs and stop immediately

Motor runs and draws more current

Question 29 of 37

Question 30 of 37

30. 69. What is the name of 3 phase motor winding, if the coil pitch is less than pole pitch?

Short chorded winding

Full pitch winding

Whole coil winding

Long chorded winding

Question 30 of 37

Question 31 of 37

31. 54. What refers coil in AC winding?

Number of turns under two similar poles

Number of turns connected in parallel

Number of turns under two dissimilar poles

Number of turns connected in series

Question 31 of 37

Question 32 of 37

32. 84. What is the reason for frequent blowing of fuse after motor running some time?

Over loading of motor

Heavy voltage fluctuation

Improper earthing

Poor insulation in winding

Question 32 of 37

Question 33 of 37

33. 52. Which type of insulating material is selected for binding the coils and over hangs?

Empire sleeves

Terylene thread

Cotton sleeves

Fibre glass tape

Question 33 of 37

Question 34 of 37

34. 53. Which insulation is used for cuffing in AC winding?

Empire fiber glass tape

Leatheroid paper

Fabric based adhesive tape

Fibre glass tape

Question 34 of 37

Question 35 of 37

35. 83. What is the effect of open circuit in rotor of an induction motor?

Motor runs with very low speed

Motor does not start

Excess vibration of shaft

Over heating in motor

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Question 36 of 37

36. 71. What is the name of the diagram used for 3phase motor winding?

End connection diagram

Development diagram

Coil connection diagram

Ring diagram

Question 36 of 37

Question 37 of 37

37. 56. Calculate the number of coils/phase/pole for a 3 phase double layer distributed winding for a motor having 36 slots, 36 coils and 4 poles.

3 coils/phase/pole

6 coils/phase/pole

9 coils/phase/pole

12 coils/phase/pole

Question 37 of 37