Chroma 66203, User Manual

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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.
3 3 2 2 1 1
i v i v i v p
+ + =
3 2 1
W W W p
+ + =
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
v v
−
and use the wattmeter on channel 2 to measure the L2 current
2
i
and L2 to
neutral voltage
) (
2
n
v v
−
as well as use the wattmeter on channel 3 to measure the L3
current
3
i
and L3 to neutral voltage
) (
3
n
v v
−
. 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.