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Figure 4.18 Measurement of three-phase balanced or unbalanced power using three single-phase
wattmeters
4.8.3 Three-Wattmeter Method
In this method, three wattmeters are used to measure three-phase power.
Three wattmeters are connected in each phase as has been shown in Fig. 4.18,
and their pressure coils are connected between each phase and the neutral.
This method is valid for the measurement of three-phase power for balanced
and unbalanced loads. The main drawback of this method is the requirement
of three wattmeters.
Example 4.11 In the two-wattmeter method of power measurement for a
three-phase load, the readings of the wattmeter are 1000 W and 550 W. What
is the power factor of the load?
Solution:
W = 1000 W
1
W = 550 W
2
Power factor of load,
