No load current of a transformer has 

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WBPSC JE Electrical 2018 (Held on 18th Feb 2018) Official Paper
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  1. high magnitude and low power factor.
  2. high magnitude and high power factor. 
  3. small magnitude and high power factor. 
  4. small magnitude and low power factor.

Answer (Detailed Solution Below)

Option 4 : small magnitude and low power factor.
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Detailed Solution

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Concept:

Transformer on no-load:

Circuit diagram for a transformer on load:

F1 Shraddha Uday 22.12.2020 D7

Where,

V1 is the applied primary voltage

IW is the working component of current through R0 (Magnetizing resistance)

Iμ  is the magnetizing component of current through X0 (magnetizing reactance)

N1 and N2 are the primary and secondary turns ratio

  • In the case of no load, the secondary terminal of the transformer is open.
  • There is no path available for the current to flow on the secondary side.
  • Hence, the transformer does not draw current from the source.
  • A small ampere of current flows through the primary transformer (no-load current I0) called excitation current (used for excitation of the core).​
  • No-load current (I0) is further divided into Iμ and IW


Phasor Diagram when transformer on no load:

F1 Shraddha Uday 22.12.2020 D8

Where,

E1 is the primary induced EMF

V1 is the primary terminal voltage

E2 is the secondary induced EMF

Power factor cos ϕ0 = (Iμ / I0) ≈ 0.2 to 0.25

Explanation:

No load current = 2 A

As the magnetizing component of current is very higher.

From the options, the magnetizing component may be 1.8 A

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