EMF Polygon MCQ

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• Machine A has 60° phase spread and machine B has 120° phase spread. Both the machines have uniformly distributed winding. The ratio of distribution factors of machine A to machine B is ____________
  ক

  0.866

  খ

  1.1

  গ

  1.55

  ঘ

  1.155
• Which among the given harmonics are called belt harmonics?
  ক

  5, 7, 11, 13

  খ

  3, 6, 9, 12

  গ

  5, 6, 11, 12

  ঘ

  7, 11, 13, 15
• For eliminating nth harmonic from the EMF generated in the phase of a 3-phase alternator, the chording angle should be ______________
  ক

  n∗full pitch

  খ

  (1/n)∗full pitch

  গ

  (2/n)∗full pitch

  ঘ

  (3/n)∗full pitch
• A 6-pole alternator with 36 slots carries a 2-phase distributed winding. Each coil is short pitched by one slot. The winding factor is given by _____________
  ক

  cot15°/3√2

  খ

  cot15°/4

  গ

  cot15°/2√2

  ঘ

  cot15°/4
• The chording angle for eliminating 5th harmonic should be ____________
  ক

  30°

  খ

  34°

  গ

  36°

  ঘ

  35°
• A 3-phase, 4-pole alternator has 48 stator slots carrying a 3-phase distributed winding. Each coil of the winding is short chorded by one slot pitch. The winding factor is given by ______________
  ক

  (cos7.5)/16

  খ

  (cot7.5)/8

  গ

  1/(8sin7.5)

  ঘ

  (cot7.5)/16
• In 48 slot, 4-pole,3 phase alternator, the coil-span is 10. Its distribution and pitch factors are respectively ____________
  ক

  0.9717,0.966

  খ

  0.9822, 0.9814

  গ

  0.9577, 0.9814

  ঘ

  0.9577, 0.966
• The pitch factor, in rotating electrical machinery, is defined as the ratio of resultant EMF of a _________
  ক

  full-pitched coil to that of a chorded coil

  খ

  full-pitched coil to the phase EMF

  গ

  chorded coil to the phase EMF

  ঘ

  chorded coil to that of a full-pitched coil
• If a stator has 48 slots, 6 poles and 3 phase with narrow spread winding, then the third harmonic belt factor is ____________
  ক

  0.9556

  খ

  0.6407

  গ

  0.1944

  ঘ

  None of the mentioned
• A 3-phase machine has integral slot winding with fundamental distribution factor kd1, the distribution factor for nth harmonic kdn is ____________
  ক

  less than kd1

  খ

  more than kd1

  গ

  equal to kd1

  ঘ

  depends upon the number of slots and poles
• The armature winding of a 2-pole, 3-phase alternator for each phase is distributed in a number of slots per phase. The RMS value of the voltage per phase is less than the RMS value of the voltage per coil multiplied by the number of coils in series because the _________
  ক

  RMS value of the voltage in different coils of the phase is different

  খ

  equal RMS voltages in different coils of the phase has mutual phase difference

  গ

  maximum value of the induced voltage in different coils of the phase are different

  ঘ

  different coils of the phase pass through different saturated regions of the magnetic circuit
• The belt factor is defined as the ratio of __________
  ক

  arithmetic sum of coil EMF to the phasor sum of coil EMFs

  খ

  phasor sum of EMF per coil to the arithmetic sum of EMF per coil

  গ

  phasor sum of coil EMFs to the arithmetic sum of coil EMFs

  ঘ

  phasor sum of coil EMFs to per phase voltage
• In a machine with coil span 9, if a coil has its one coil-side in slot 1, then its other coil-side must be in ____________
  ক

  slot 9

  খ

  slot 8

  গ

  slot 10

  ঘ

  slot 2
• What is the coil span for a 2 pole 18 slot machine?
  ক

  9

  খ

  4.5

  গ

  18

  ঘ

  6
• The angular slot pitch, γ is given by __________
  ক

  γ = πP/Total number of slots Elect radians

  খ

  γ = 180P/Total number of slots Elect degrees

  গ

  γ = 180/Slots per pole Elect degrees

  ঘ

  Any of the mentioned