Issue
How Neutral Current (Current N or I4) is calculated or measured in PM8000?
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Product Line
PM8000 series meters
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Environment
Power Monitoring Expert (PME)
ION Setup
Modbus mastering
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Solution
As stated in PM8000 Modbus Register Map, there is a Register named: Current N with Modbus Register 3006 which is also named as I4.

When PM8000 meter is setup with volts mode 4W-WYE, I4 Modbus Register will display a value for the current value when:
A: I4+ and I4- terminals are wired as 3CT Wiring with specific wiring of -(I1+I2+I3). Refer to Image 1.
or
B: I4+ and I4- terminals are wired as 4CT Wiring. Refer to Image 2.

Image1:


Image 2:


Note: Under both above wiring connections, the value of I4 on the meter is affected by the I4 CT ratio.

Image 3



The PM8000 has another register, I5 at Modbus register 3008, with label Current G. This current is the residual current -(I1+I2+I3+I4). When meter wired as shown in image 1, I5 will always be zero.

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