Q.1
In a D.C. machine, the value of peripheral speed should not, normally, exceed
  • 10 m/s
  • 20 m/s
  • 30 m/s
  • 40 m/s
Q.2
In a D.C. machine the current per brush arm should not be more than
  • 100 A
  • 200 A
  • 300 A
  • 400 A
Q.3
In a D.C. machine the number of brush arms is _____ the number of poles.
  • less than
  • equal to
  • greater than
  • none of the above
Q.4
The weight of copper of both armature and field windings decreases with _____ innumber of poles.
  • increase
  • decrease
  • either of the above
  • none of the above
Q.5
Which of the following problem arises in D.C. motors which are fed from thyristorbridge circuits ?
  • Increased I R losses
  • Increased core losses
  • Poor commutation
  • All of the above
Q.6
________ is the common method of applying brushes to the commntator.
  • Radial
  • Trailing
  • Reaction
  • All of the above
Q.7
Which of the following brushes can be used for high values of current density ?
  • Metal graphite brushes
  • Hard carbon brushes
  • Electro-graphitic brushes
  • Natural graphite brushes
Q.8
______ brushes are fragile and cause excessive wear of commutator,
  • Natural graphite
  • Hard carbon
  • Electro graphitic
  • Metal graphite
Q.9
The laminations of the armature of a D.C. machine are usually _____ thick.
  • 0.1 to 0.2 mm
  • 0.2 to 0.3 mm
  • 0.3 to 0.4 mm
  • 0.4 to 0.5 mm
Q.10
A practical formula for determining the thickness of insulation between low voltageand high voltage windings is
  • 1 + 0.2 kVmm
  • 2 + 0.5 kVmm
  • 4 + 0.7 kV mm
  • 5 + 0.9 kV mm
Q.11
Dummy coil should not be used in
  • small machines
  • large machines
  • either (a) or (b)
  • none of the above
Q.12
Power transformers have rating
  • equal to 50 kVA
  • equal to 100 kVA
  • above 200 kVA
  • none of the above
Q.13
Power transformers should be designed to have maximum efficiency
  • at one-fourth load
  • at one-half load
  • at or near full load
  • any of the above
Q.14
In transformers using hot rolled steel, the cross-section of the yoke is made about _____ greater than that of the core
  • 5 percent
  • 10 percent
  • 15 percent
  • 30 percent
Q.15
Yokes with rectangular cross-section are used for
  • small capacity transformers
  • medium capacity transformers
  • large capacity transformers
  • any of the above
Q.16
The cold rolled grain oriented steel has ______ permeability in the direction of thegrain orientation.
  • minimum
  • maximum
  • nil
  • none of the above
Q.17
Cylindrical windings using circular conductors, employed in transformers, are
  • single layered
  • double layered
  • multi-layered
  • none of the above
Q.18
Helical windings are used in
  • distribution transformers
  • power transformers
  • shell type transformers
  • none of the above
Q.19
Multi-layer helical windings are commonly used in the transformers as high voltagewindings
  • upto 20 kV
  • upto 50 kV
  • upto 80 kV
  • for 110 kV and above
Q.20
Disc windings are primarily used in
  • short capacity transformers
  • medium capacity transformers
  • high capacity transformers
  • any of the above
Q.21
The heat dissipating capability of transformers of ratings higher thankVA inincreased by providing which of the following ?
  • Corrugations
  • Fins
  • Tubes
  • All of the above
Q.22
Transformers with a capacity of upto _____ have a cooling radiator system with naturalcooling
  • 2 MVA
  • 5 MVA
  • 7.5 MVA
  • 10 MVA
Q.23
The forced oil and air circulation method is usual one for transformers of capacities
  • upto 5 MVA
  • upto 10 MVA
  • upto 20 MVA
  • 30 MVA upwards
Q.24
The flash point of transformer oil should be higher than
  • 40°C
  • 60°C
  • 80°C
  • 104°C
Q.25
D.C. windings are
  • sometimes 2-layer type
  • never 2-layer type
  • always 2-layer type
  • none of the above
Q.26
The stator of a D.C. machine comprises of
  • main poles
  • interpoles
  • frame
  • all of the above
Q.27
D.C. servomotors are used in
  • purely control systems
  • purely A control systems
  • both and A control systems
  • none of the above
Q.28
Which of the following in an application of D.C. motors?
  • Traction
  • Drives for process industry
  • Battery driven vehicles
  • All of the above
Q.29
The surge phenomenon is particularly important in case of
  • low voltage transformers
  • medium voltage transformers
  • high voltage transformers
  • any of the above
Q.30
The cylindrical windings using circular conductors are used for current rating of
  • upto 20 A
  • upto 40 A
  • upto 60 A
  • upto 80 A
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