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A 3-phase, star-connected, balanced load is supplied from a 3-phase, 400 V (rms), balanced voltage source with phase sequence R-Y-B, as shown in the figure. If the wattmeter reading is -400 W and the line current is I_R = 2 A (rms), then the power factor of the load per phase is
- Unity
- 0.5 leading
- 0.866 leading
- 0.707 lagging
Correct answer: 0.5 leading
Solution
The power factor is calculated using the formula for real power in a balanced three-phase system, which relates the total power, line current, and phase voltage. Given the negative wattmeter reading indicates a leading power factor, and the calculated value aligns with 0.5, it confirms that the load is indeed operating at a 0.5 leading power factor.
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