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ADE7953 integration

Question asked by TrezTan on May 7, 2015
Latest reply on Jun 4, 2015 by hmani

Hi ADI engineers,

 

We have made a prototype board based on the ADE7953 Evaluation board but we are facing 2 issues:
- voltage reading drops with load
- no accurate current reading.

For voltage measurement.
- We are using AC voltage from Neutral and Line.
Neutral is shorted to the ship ground and we use a 1:1000 attenuation circuit for the Line (220VAC).
One strange behaviour is that when we put a heavy load the reading voltage drops of 30~40V
- Another issue we got, with the schematic from the EVB, the line and phase cannot be swapped.

For current reading.
- We use a current transformer with following specs: turn ratio 1:2000, input 5A (25A max) , output 2.5mA.
Our real input current will go from 0A to 20A max.

As per AN639 and its burden resistor calculation formula, it should be 7 or 14 ohms, but AN564 and AN563 show different way to connect that burden resistor and we are not sure which one to use correctly.

 

Attached is the schematic for the ADE7953.
We put jumper JP5, JP8, JP12, JP16, JP18 and JP22.

DVDD is 3.3V and there is no external reference 1.2V used.
AGND and DGND are connected under U10 via the exposed pad.

IA and IB channels are to measure 2 different current (load) from the main LINE.

Also, the ADE7953 circuit is not isolated from our microcontroller on the same board, but we plan to separate both circuits in a new design.

Please help to advise.

Thank you

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