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Mr.Orange asked

VM-3P75CT wrong calculations for watts

New Victron energy meter (VM-3P75CT) the power for L1 is constantly wrong. The math doesn't make sense. 123V and 1.1 amps is not 14.9 watts. This just started happening a few days ago. I have a Carlos Gavazzi EM530 Connected to the exact same wires and location. EM530 When I installed the new meter a few weeks ago. The values matched each other. for a few weeks. I used Cerbo device list and a Custom Widget VRM graph to compare values. Unit is running the latest Firmware (1.05) The Cerbo GX is running latest firmware 3.14. I don't believe the Cerbo firmware has anything to do with this problem since the wrong values are seen in Victron connect, remote consol and VRM.

I did try loading old firmware on the energy meter (1.03) and Cerbo firmware 3.13 and 3.12 Reverting firmware did not fix the issue.

What can

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Energy Meter
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1 Answer
ldoes (Victron Energy) avatar image
ldoes (Victron Energy) answered ·

The reported current for the VM-3P75CT is the so called "RMS" current and the reported power is the so called "real" power. You might see a difference between the reported power and voltage * current, especially at low powers, because of low power-factor or distortion current in the system.

The value obtained from calculating voltage * current is called apparent power (in volt-amperes), and is always greater than or equal to the real power (in watts).

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That does not explain the difference between measured power for the VM-3P75CT and EM530 however. My best guess is that the current transformer on L1 is either broken, or not clamped correctly.


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