1. Which of the following is the major consideration to evolve a good design ?
2 ________ impose limitation on design.
3. The efficiency of a machine should be as ______ as possible to reduce the operating cost.
4. If an insulating material is operated beyond the maximum allowable temperature, its life is
5. The design of mechanical parts is particularly important in case of _____ speed machines.
6. In induction motors, the length of air gap in kept as small as mechanically possible is order to have
7. In ______ machines, the size of the shaft is decided by the critical speed which depends on the deflection of the shaft.
8. The length of air gap to be provided in ______ is primarily determined by power factor consideration.
9. Electrical machines having a power output upto about 750 W may be called _______machines.
10. Electrical machines having power outputs ranging from a few kW upto approximately 250 kW may be classified as
11. Commercial available medium size machines have a speed range of ______ .
12. The action of electromagnetic machines can be related to which ofthe following basic principles ?
13. The change in flux linkages can be caused in which of the following ways ?
14 ______ is universally used for windings of electrical machines because it is easily workable without any possibility of fracture.
15. Aluminium when adopted as a conductor material in ______ transformers, decreases the overall cost of the transformer
16. Which of the following materials is used in the manufacture of resistance grids to be used in the starters of large motors ?
17. Materials exhibiting zero value of resistivity are known as ______ .
18. ________ has a lowrelative permeability and is used principally in field frames when cost is of primary importance and extra weight is not objectionable.
19 ______is extensively used for those portions of magnetic circuit which carry steady flux and need superior mechanical properties ?
20. Hot rolled sheets have ______ value of permeability.
21. The heated parts of an electrical machine dissipate heat into their surroundings by which of the following modes of heat dissipation ?
22. The heat dissipated by ______ from a surface depends upon its temperature and its characteristics like colour, roughness etc.
23. The mcrease in heat dissipation by air blasts is due to increase in
24. On which of the following variables heat convected depends ?
25. Which of the following methods is used for air cooling of turbo-alternators ?
26. Multiple inlet system of air cooling of turbo-alternators can be used for machines of rating upto
27. Which of the following is an advantage of hydrogen cooling ?
28. The density of hydrogen is _____ times the density of air.
29. Hydrogen has a heat transfer co-efficient _____ times that of air.
30. The thermal conductivity of hydrogen is ______ times that of air.
31. With conventional hydrogen cooling it is possible to increase the rating of a single unit to
32. The noise produced by a ______ cooled machine is less as the rotor moves in a medium of smaller density.
33 cooling is the process of dissipating the armature and field winding losses to a cooling medium circulating within the winding insulation wall
34. Machines cooled by direct cooling method may be called
35. In direct cooled system using hydrogen both stator and rotor conductors are made
36. With direct water cooling it is possible to have ratings of about
37. The resistivity of water should not be less than
38. Direct water cooling of rotor winding presents
39. The time taken by the machine to attain 0.632 of its final steady temperature rise is called
40. In self cooled motors the cooling time constant is about ______ than the heating time constant because cooling conditions are worse at standstill.
41. By which of the following methods motor rating for variable load drives can be determined ?
42. Which of the following methods does not take into account the maximum temperature rise under variable load conditions ?
43. Which of the following methods is most accurate ?
44. By which of the following methods the temperature rise of windings and other parts may be determined ?
45. The slot leakage can be calculated by making which of the following assumptions ?
46. The value of exciting or magnetizing current depends upon which of the following factors ?
47. Tractive magnets are operated from ______.
48 electromagnets generally function as holding magnets.
49. Which of the following is the commonly used type of electromagnets ?
50 _______ are used for construction of core of electromagnets.
51. The design of electromagnets is based upon which of the following fundamental equations ?
52. When the two coil sides forming a coil are spaced exactly one pole pitch apart they are said to be of ______.
53 ________ are always double layer type.
54. The distance between the starts of two consecutive coils measured in terms of coil sides is called
55. The winding where dummy coils are used is sometimes called
56. Dummy coil should not be used in ______.
57. Power transformers have rating ______.
58. Power transformers should be designed to have maximum efficiency
59. In transformers using hot rolled steel, the cross-section of the yoke is made about _____ greater than that of the core
60. Yokes with rectangular cross-section are used for
61. The cold rolled grain oriented steel has ______ permeability in the direction of the grain orientation.
62. Cylindrical windings using circular conductors, employed in transformers, are
63. Helical windings are used in ______.
64. Multi-layer helical windings are commonly used in the transformers as high voltage windings
65. Disc windings are primarily used in ______.
66. The heat dissipating capability of transformers of ratings higher than 30 kVA in increased by providing which of the following ?
67. Transformers with a capacity of upto _____ have a cooling radiator system with natural cooling
68. The forced oil and air circulation method is usual one for transformers of capacities
69. The flash point of transformer oil should be higher than
70. The voltage control in electric supply networks in required on account of which of the following reasons ?
71. D.C. windings are _______.
72. The usual values of maximum flux densities for distribution transformers using hot rolled silicon steel are
73. For 275 kV transformers, using cold rolled grain oriented steel, which of the following values of flux density may be used?
74. For large power transformers, self oil cooled type or air blast type which of the following values of current density may be used ?
75. A current density of _____ is ilsed for large power transformers with forced circulation of oil or with water cooling coils
76. The high voltage winding is usually which of the following type ?
77. Which of the following is the basic consideration in the design of insulation ?
78. A practical formula for determining the thickness of insulation between low voltage and high voltage windings is
79. The insulation between windings and grounded core and the insulation between the windings of the same phase is called
80. The cylindrical windings using circular conductors are used for current rating of
81. The surge phenomenon is particularly important in case of _______.
82. Which of the following in an application of D.C. motors?
83. D.C. servomotors are used in _______.
84. The stator of a D.C. machine comprises of _______.
85. The laminations of the armature of a D.C. machine are usually _____ thick.
86. _______ is usually used for brush rockers
87. ______ brushes are fragile and cause excessive wear of commutator.
88. Which of the following brushes can be used for high values of current density ?
89 ________ is the common method of applying brushes to the commntator.
90. Which of the following problem arises in D.C. motors which are fed from thyristor bridge circuits ?
91. The weight of copper of both armature and field windings decreases with _____ in number of poles.
92. In a D.C. machine the number of brush arms is _____ the number of poles.
93. In a D.C. machine the current per brush arm should not be more than
94. In a D.C. machine, the value of peripheral speed should not, normally, exceed
95. In D.C. machines the width of the duct is usually
96. D.C. machines designed with a large value of air gap length have
97. In D.C. machines, or order to prevent excessive distortion of field form by the armature reaction, the field mmf must be made
98. In D.C. machines, the ____ in field mmf results in increase in size and cost of machines.
99. The operation of a D.C. machine with large air gap lengths is comparatively
100. Which of the following methods may be adopted to reduce the effects of armature reaction ?
2 ________ impose limitation on design.
3. The efficiency of a machine should be as ______ as possible to reduce the operating cost.
4. If an insulating material is operated beyond the maximum allowable temperature, its life is
5. The design of mechanical parts is particularly important in case of _____ speed machines.
6. In induction motors, the length of air gap in kept as small as mechanically possible is order to have
7. In ______ machines, the size of the shaft is decided by the critical speed which depends on the deflection of the shaft.
8. The length of air gap to be provided in ______ is primarily determined by power factor consideration.
9. Electrical machines having a power output upto about 750 W may be called _______machines.
10. Electrical machines having power outputs ranging from a few kW upto approximately 250 kW may be classified as
11. Commercial available medium size machines have a speed range of ______ .
12. The action of electromagnetic machines can be related to which ofthe following basic principles ?
13. The change in flux linkages can be caused in which of the following ways ?
14 ______ is universally used for windings of electrical machines because it is easily workable without any possibility of fracture.
15. Aluminium when adopted as a conductor material in ______ transformers, decreases the overall cost of the transformer
16. Which of the following materials is used in the manufacture of resistance grids to be used in the starters of large motors ?
17. Materials exhibiting zero value of resistivity are known as ______ .
18. ________ has a lowrelative permeability and is used principally in field frames when cost is of primary importance and extra weight is not objectionable.
19 ______is extensively used for those portions of magnetic circuit which carry steady flux and need superior mechanical properties ?
20. Hot rolled sheets have ______ value of permeability.
21. The heated parts of an electrical machine dissipate heat into their surroundings by which of the following modes of heat dissipation ?
22. The heat dissipated by ______ from a surface depends upon its temperature and its characteristics like colour, roughness etc.
23. The mcrease in heat dissipation by air blasts is due to increase in
24. On which of the following variables heat convected depends ?
25. Which of the following methods is used for air cooling of turbo-alternators ?
26. Multiple inlet system of air cooling of turbo-alternators can be used for machines of rating upto
27. Which of the following is an advantage of hydrogen cooling ?
28. The density of hydrogen is _____ times the density of air.
29. Hydrogen has a heat transfer co-efficient _____ times that of air.
30. The thermal conductivity of hydrogen is ______ times that of air.
31. With conventional hydrogen cooling it is possible to increase the rating of a single unit to
32. The noise produced by a ______ cooled machine is less as the rotor moves in a medium of smaller density.
33 cooling is the process of dissipating the armature and field winding losses to a cooling medium circulating within the winding insulation wall
34. Machines cooled by direct cooling method may be called
35. In direct cooled system using hydrogen both stator and rotor conductors are made
36. With direct water cooling it is possible to have ratings of about
37. The resistivity of water should not be less than
38. Direct water cooling of rotor winding presents
39. The time taken by the machine to attain 0.632 of its final steady temperature rise is called
40. In self cooled motors the cooling time constant is about ______ than the heating time constant because cooling conditions are worse at standstill.
41. By which of the following methods motor rating for variable load drives can be determined ?
42. Which of the following methods does not take into account the maximum temperature rise under variable load conditions ?
43. Which of the following methods is most accurate ?
44. By which of the following methods the temperature rise of windings and other parts may be determined ?
45. The slot leakage can be calculated by making which of the following assumptions ?
46. The value of exciting or magnetizing current depends upon which of the following factors ?
47. Tractive magnets are operated from ______.
48 electromagnets generally function as holding magnets.
49. Which of the following is the commonly used type of electromagnets ?
50 _______ are used for construction of core of electromagnets.
51. The design of electromagnets is based upon which of the following fundamental equations ?
52. When the two coil sides forming a coil are spaced exactly one pole pitch apart they are said to be of ______.
53 ________ are always double layer type.
54. The distance between the starts of two consecutive coils measured in terms of coil sides is called
55. The winding where dummy coils are used is sometimes called
56. Dummy coil should not be used in ______.
57. Power transformers have rating ______.
58. Power transformers should be designed to have maximum efficiency
59. In transformers using hot rolled steel, the cross-section of the yoke is made about _____ greater than that of the core
60. Yokes with rectangular cross-section are used for
61. The cold rolled grain oriented steel has ______ permeability in the direction of the grain orientation.
62. Cylindrical windings using circular conductors, employed in transformers, are
63. Helical windings are used in ______.
64. Multi-layer helical windings are commonly used in the transformers as high voltage windings
65. Disc windings are primarily used in ______.
66. The heat dissipating capability of transformers of ratings higher than 30 kVA in increased by providing which of the following ?
67. Transformers with a capacity of upto _____ have a cooling radiator system with natural cooling
68. The forced oil and air circulation method is usual one for transformers of capacities
69. The flash point of transformer oil should be higher than
70. The voltage control in electric supply networks in required on account of which of the following reasons ?
71. D.C. windings are _______.
72. The usual values of maximum flux densities for distribution transformers using hot rolled silicon steel are
73. For 275 kV transformers, using cold rolled grain oriented steel, which of the following values of flux density may be used?
74. For large power transformers, self oil cooled type or air blast type which of the following values of current density may be used ?
75. A current density of _____ is ilsed for large power transformers with forced circulation of oil or with water cooling coils
76. The high voltage winding is usually which of the following type ?
77. Which of the following is the basic consideration in the design of insulation ?
78. A practical formula for determining the thickness of insulation between low voltage and high voltage windings is
79. The insulation between windings and grounded core and the insulation between the windings of the same phase is called
80. The cylindrical windings using circular conductors are used for current rating of
81. The surge phenomenon is particularly important in case of _______.
82. Which of the following in an application of D.C. motors?
83. D.C. servomotors are used in _______.
84. The stator of a D.C. machine comprises of _______.
85. The laminations of the armature of a D.C. machine are usually _____ thick.
86. _______ is usually used for brush rockers
87. ______ brushes are fragile and cause excessive wear of commutator.
88. Which of the following brushes can be used for high values of current density ?
89 ________ is the common method of applying brushes to the commntator.
90. Which of the following problem arises in D.C. motors which are fed from thyristor bridge circuits ?
91. The weight of copper of both armature and field windings decreases with _____ in number of poles.
92. In a D.C. machine the number of brush arms is _____ the number of poles.
93. In a D.C. machine the current per brush arm should not be more than
94. In a D.C. machine, the value of peripheral speed should not, normally, exceed
95. In D.C. machines the width of the duct is usually
96. D.C. machines designed with a large value of air gap length have
97. In D.C. machines, or order to prevent excessive distortion of field form by the armature reaction, the field mmf must be made
98. In D.C. machines, the ____ in field mmf results in increase in size and cost of machines.
99. The operation of a D.C. machine with large air gap lengths is comparatively
100. Which of the following methods may be adopted to reduce the effects of armature reaction ?
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