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GATE 2014 EE (EE2) – Question 30

Electrical and Electronic Measurements · Measurement of voltage, current, power, energy and power factor · 1 mark · Numerical answer

Two wattmeters read 100 W and 250 W for a balanced three-phase load. Find load power factor.

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Correct answer: 0.78 to 0.82

Explanation

For a balanced three-phase load,tanφ=√3|W1−W2|/(W1+W2)=√3×150/350≈0.742307. Therefore cosφ=1/√(1+tan²φ)=**0.802955**. Both readings are positive; their sum350W is the total real power.