Electronic Electrical Devices  Electronic Electrical Components
Three Phase Watt Meter Review
Total power in a 3Theta circuit is the sum of the powers of the separate phases. The total power
could be measured by placing a wattmeter in each phase See below; however, this method is
not feasible since it is often impossible to break into the phases of a delta load. It also may not
be feasible for the Y load, since the neutral point to which the wattmeters must be connected is
not always accessible.
Normally, only two wattmeters are used in making 3Theta power measurements .
In balanced 3Theta systems, with any power factor, total power is calculated by adding the A and
B phase powers. The equation below is the mathematical representation for calculating total power
(PT).
P_{T} = W_{A} + W_{B}
Where: W_{A} and W_{B} are the power readings in Phase A and Phase B.
