This two wattmeter method calculator finds total three-phase power and the power factor from two wattmeter readings. Enter W1 and W2 above to get the results instantly.
Formulas
Total power P = W1 + W2 tan φ = √3 × (W1 − W2) ÷ (W1 + W2) Power factor = cos φ
Example
W1 = 1200 W, W2 = 800 W: P = 2000 W; tanφ = √3 × 400 ÷ 2000 = 0.346, so PF = 0.945.
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Frequently Asked Questions
What is the two-wattmeter method?
It measures three-phase power with two wattmeters. Total power is the sum of the two readings, valid for balanced or unbalanced loads.
How do I get power factor from two wattmeters?
Compute tan phi as the square root of 3 times the reading difference over the sum, then take the cosine.
Can a wattmeter read negative?
Yes. At low power factors one wattmeter can read negative, and you subtract it in the total.