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GATE 2014 EE (EE1) – Question 29

Electrical and Electronic Measurements · Measurement of voltage, current, power, energy and power factor · 1 mark · Multiple choice

Two wattmeters measure power of a balanced three-phase, three-wire load. The first reads twice the second. Find load-impedance angle (rad).

  1. $\pi/12$
  2. $\pi/8$
  3. $\pi/6$
  4. $\pi/3$

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Correct answer: (C) $\pi/6$

Explanation

For a balanced three-phase load, tanφ=√3(W1−W2)/(W1+W2). With W1=2W2, tanφ=√3/3, giving the conventional lagging load angle **φ=π/6,C**. Without a lead/lag convention the readings determine the angle magnitude.