GATE EE 2023 Set 1 — Question 39
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Electric Circuits → AC Power & Three-Phase → Three-Phase Power Measurement
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Question
A 3-phase, star-connected, balanced load is supplied from a 3-phase, V (rms), balanced voltage source with phase sequence R-Y-B, as shown in the figure. If the wattmeter reading is W and the line current is A (rms), then the power factor of the load per phase is
Correct answer
(C) 0.866 leading
Solution
1.Identify the wattmeter connection: The current coil (CC) is in line R, and the pressure coil (PC) is connected between lines Y and B. The wattmeter reading is given by , where is the phase angle between the voltage and the current .
2.Phasor Analysis: For a balanced 3-phase system with R-Y-B sequence:
- The line-to-line voltage .
4.Wattmeter Reading Equation: The angle between and is .
.5.Calculate : Given W, V, and A:
.
6.Power Factor: The power factor is . Since the phase angle is negative, the current leads the voltage, indicating a leading power factor.
Therefore, the power factor is 0.866 leading.Continue learning with Success Tracker
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