In a 3-phase power measurement by two wattmeter method the reading of one of the wattmeter was zero. The power factor of the load must be_______________?
Correct answer: B. 0.5
- A. unity
- B. 0.5
- C. 0.3
- D. zero
Explanation
In the two-wattmeter method, one reading becomes zero when the load angle is 60°, because one wattmeter measures a term proportional to cos(30° + 60°). Thus the power factor is cos 60° = 0.5.
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