If P is the power of a star connected system, then what will be the power of an equivalent delta connected system?

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WBPSC JE Electrical 2018 (Held on 18th Feb 2018) Official Paper
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  1. P
  2. 2 P
  3. P/3
  4. 3 P

Answer (Detailed Solution Below)

Option 4 : 3 P
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Detailed Solution

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The correct answer is option 4): 3 P

Concept:

Let the star-connected system is denoted as (Y)

VL is the line voltage

Vph is the phase voltage

Iis the line current

Iph is the phase current

Vph = \(V_L\over \sqrt(3)\)

IL = IPh = \(V_{ph}\over R\)

Power = 3 × Iph2 × R

P\(V_L^2 \over R\)

For delta connection ( Δ )

IL = \( I_{Ph} \over \sqrt{3}\) \(V_{ph} \over R\)

PΔ  = 3 × Iph2 × R

= 3 × (\(V_{ph} \over R\))2 × R

PΔ =  3 × \(V_L^2 \over R\)

PΔ  =  3 × PY

Hence option 4 is correct

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