Power in Three-Phase Circuit by Three-Wattmeter Method

Author: E.E. Kimberly

The power in a three-phase system may be measured by placing a single-phase wattmeter in each phase and adding the three readings. This method is possible in a A system only if the phase units can be separated and in a Y-system only if the neutral or wye point can be reached. Fig. 9-5 shows the proper arrangement of wattmeters. In either (a) or (b),

Fig. 9-5. Measurement of 3-Phase Power by Three-Wattmeter Method

By equation (9-1), in which V₀1 is used instead of V₀2, Therefore,

and

(9-4)

This value is the power factor of the balanced system whether Δ-connected or Y-connected.