While measuring power in three phase load by two wattmeter

Home » Electrical and Electronics Measurements » Electrical and electronics measurements miscellaneous » Question

While measuring power in three phase load by two wattmeter method, the reading of the two wattmeters will be equal and opposite when

1. power factor is unity
2. load is balanced
3. phase angle is between 60° and 90°
4. the load is purely inductive

Correct Option: D

The wattmeter readings are proportional to cos (30 + θ).
When θ = 90°, the two quantities are equal and opposite. Therefore, when the load is purely inductive or capacitive, the given situation will occur.