300 Important DC Generator MCQ Question and Answer | PDF Free Download
1.Width of a carbon brush in a DC machine should be equal to
- ALess than the width of one commutator segment
- BThe width of 1 to 2 commutator segments
- CThe width of 2 to 3 commutator segments
- DThe width of more than 3 commutator segments
2.A duplex lap winding with equalizers and even number of pairs of poles is
- ADoubly re-entrant and number of coils per pair of poles is an odd integer
- BDouble re-entrant and number of coils per pair of poles is an even integer
- CSingly entrant and number of coils per pair of poles is an even integer
- DSingly entrant and number of coils per pair of poles is an odd integer
3.Wave winding is composed of
- AAny odd number of conductors
- BAny even number of conductors
- CThat even number which is exact multiple of poles ?2
- DThat even number which is exact multiple of poles
4.For a 4-pole machine wave winding is impossible with __________ armature conductors
- A30
- B32
- C34
- D38
5.In a dc machine for the same value of , Z and N; which one of the following statements is correct?
- AArmature emf is more with wave winding than with lap winding
- BArmature emf is less with wave winding than with lap winding
- CArmature emf depends on whether the machine is running as a motor or a generator
- DArmature emf is same as long as the flux density in the air gap remains the same
6.The dummy coils in dc machines are provided to
- AIncrease the efficiency
- BImprove the commutation
- CReduce the cost of the machine
- DMaintain mechanical balance of armature
7.A homopolar generator usually has
- AHigh voltage and high current
- BLow voltage and high current
- CLow voltage and low current
- DHigh voltage and low current
8.In a dc generator, the ripples in the direct emf generated are reduced by employing
- ACommutator with large number of segments
- BEqualizer rings
- CCarbon brushes
- DGraphite brushes
9.In order to ascertain whether a dc machine is lap wound or wave wound on the basis of visual observation of the armature, one should observe the
- AConnections to the brushes
- BConnections to the commutator
- CConnections to the field winding
- DDirection of end connections
10.The coil span
- AMust be exactly equal to pole pitch
- BCan never be equal to pole pitch
- CMay or may not be exactly equal to pole pitch
- DNone of the above
11.The commutator pitch for simplex lap winding is
- A+1
- B-1
- C+1 or -1
- DAverage pitch
12.The commutator pitch for simplex wave winding is equal to
- A+1 or-1
- BTwice average pitch
- CAverage pitch
- DHalf average pitch
13.In a dc machine armature winding, the number of commutator segments is equal to the number of armature
- ACoils
- BCoil sides
- CConductors
- DTurns
14.How many segments will be there for the commutator of a 6-pole dc machine having a simple wave wound armature with 72 slots
- A73
- B72
- C71
- D70
15.For both lap and wave windings, there are as many commutator bars as the number of
- AArmature conductors
- BWinding elements
- CPoles
- DSlots
16.In a drum type dc armature winding the back pitch and front pitch in terms of the coil sides must be
- Aeven and odd respectively
- Bodd and even respectively
- Cboth even
- Dboth odd
17.In a dc machine, fractional pitch winding is employed to
- Aincrease generated voltage
- Breduce sparking
- Csave copper
- Dboth (b) and (c)
18.In a dc machine, the armature winding is made up of number of coils distributed in large number of armature slots instead of placing all the coils into two slots to
- Ahave maximum emf at the output terminals
- Bhave maximum emf generated in the armature
- Chave minimum heat dissipation from the armature
- Dmake the armature dynamically balanced
19.Aluminum is not used as winding wire for the armature of dc machine because it
- AIs costlier
- BIs of low resistivity
- CIs of lower thermal conductivity
- DRequires large winding space
20.Short circuiting in the armature winding is caused due to
- AFailure of insulation between two turns of a coil
- BFailure of insulation between two commutator bars
- CGrounding of two or more turns of the same coil
- DAny of the above