Electrical machines miscellaneous

Electrical machines miscellaneous

Easy Questions
Moderate Questions

Electrical Machines

Electrical machines miscellaneous
  1. An auto-transformer having a transformation ratio of 0.8 supplies a load of 10 kW. The power transferred inductively from the primary to the secondary is _______ kW .








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    If transformation ratio were unity, whole power would have been transferred conductively only. Power transferred inductively

    = Total poewr × 1 -
    N2
    		 = 10 × (1 - 0.8) = 2 kW
    N1

    Correct Option: B


    If transformation ratio were unity, whole power would have been transferred conductively only. Power transferred inductively

    = Total poewr × 1 -
    N2
    		 = 10 × (1 - 0.8) = 2 kW
    N1

  1. A 2 kVA transformer has iron loss of 150 Watts and full - load copper loss of 250 Watts. The maximum efficiency of the transformer would occur when the total loss is _______ W .








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    When variable loss becomes equal to constant loss, efficiency is maximum. Thus at maximum efficiency of this transformer, total loss = 150 × 2 = 300 W

    Correct Option: D

    When variable loss becomes equal to constant loss, efficiency is maximum. Thus at maximum efficiency of this transformer, total loss = 150 × 2 = 300 W

  1. The voltage regulation of a transformer at full load and 0.8 power factor lagging is 2.5%. The voltage regulation at full load, 0.8 power factor leading will be _______ % .








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    ∈ = ∈r cos θ + ∈x sin θ
    If we take 2.5= 1.75 + 0.75 then at leading power factor load,
    ∈ = ∈r cos φ – ∈x sin φ = 1.75 – 0.75 = 1.0%

    Correct Option: B

    ∈ = ∈r cos θ + ∈x sin θ
    If we take 2.5= 1.75 + 0.75 then at leading power factor load,
    ∈ = ∈r cos φ – ∈x sin φ = 1.75 – 0.75 = 1.0%

  1. An auto transformer having a transformation ratio of 0.8 supplies a load of 3 kW. The power transferred conductively from primary to secondary is _______ kW .








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    NA

    Correct Option: C

    NA

  1. For a 1.15 kVA, 460/230 V transformer connected to a standard single phase 50 Hz supply, the no load current is likely to be _______ A .








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    NA

    Correct Option: A

    NA