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ADE7878A calibration process

Category: Software
Product Number: ade7878


I'm facing some troubles using the Energy Meter ADE7878AACPZ.
We are developing an 3 phases AC power supply wich uses the ADE7878A to measure the outputs.
This supply does not requires high current on it's output, wich in our case is 6A.

We follow the AN-1076 to implement the calibration process, wich in our case is the "Accurate Source Method".
We have implemented the calibration process on this sequence:
-Calibration of the xIGAIN and xVGAIN Registers;
-Calibration of the IRMSOS and VRMSOS Registers;
-Calibration of the xPHCAL Registers;
-Calibration of the WGAIN Registers.

We have a nominal current of IN=6A. Our full scale current is IFS = 12,73A. We tried two different current transformers, one of them is the AC1020 (IN = 20A 1000:1) and the second is the HMCT103C - 5A/5mA.

On both cases we had a perfect result on the nominal current (6A), something like 0,05% of error (power factor 1) an something biger but near to it on power factor 0,5.
We check the error reading the pulses on kw/hr (using 6400imp/kwh as the AN-1076 suggests). We have a RADIAN 3 phase reference standard to do this.

The issue is that when we decrease the current to 1A, our error increases to 0,8%. This occurs on both current transformers. It looks like the issue is connected the current angle, but taking the second current transformer we are using as example, we are at 20% of it's nominal current. We tested it on 6 different transformers to exclude a production fail.
We have another prototipe here where we use a different chip, from another manufacture and we do not have this behavior.
If necessary, I can provide schematics, code and whatever you need to help us.

Edit ADE7878 to ADE7878A
[edited by: TiagoMagSilva at 6:34 PM (GMT -5) on 16 Jan 2024]