Digital Power Meter 66203/66204 User’s Manual
4-48
Figure 4-72 Three-Wattmeter Method Wiring
4.7.5 Selecting 3P4W Wiring Mode, Three-Wattmeter
Method
Taking the example of Y connection 3-phase power measurement, it uses 3 power meters to
grab the individual instantaneous power of 3 phases simultaneously and calculate the
average power of each phase and then sum up to get the total power.
332211
ivivivp ++=
321
WWWp ++=
From the formula above, it can use three wattmeters to measure the power of 3 phases that
is to use the wattmeter on channel 1 to measure the L1 current
1
i and L1 to neutral voltage
)(
1 n
vv − and use the wattmeter on channel 2 to measure the L2 current
2
i and L2 to
neutral voltage
)(
2 n
vv − as well as use the wattmeter on channel 3 to measure the L3
current
3
i and L3 to neutral voltage )(
3 n
vv
. The advantage of using three-wattmeter
method is that it can measure the power and neutral voltage of every phase directly. It can
also use the 4
th
channel of the 66204 Digital Power Meter to measure the neutral current
under the unbalanced power system or use the current of each phase for calculation.
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