Proof, Two-Wattmeter Power Measurement (3 Phase)

Thread Starter


Joined Sep 13, 2010
See figure attached.

We are supposed to show that for a balanced three-phase power system that the sum of the readings of the two devices is indeed equal to the three-phase power.

How do I go about showing this?

Can someone give me a hint as to where to start?

I can see that Vab, and Vcb will be the line voltages, but I'm still not sure where to start.



Joined Mar 6, 2009
Draw the phasor diagram and the approach becomes more obvious. In any case there are numerous on-line examples of the proof. Google "two watt meter method three phase power".

I have a "proof" of my own - if you are interested I'll post a copy.
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