Need example to connect current transformer to ADE7933

Hi Fausto Bartra,

The ADE7933 is an isolated ADC most typically meant for use with a shunt current sensor. If you are using a current transformer then isolation is already present in the transformer.

Could you tell me more about the application? Maybe there is a more appropriate metering IC to choose from with use with CT's. Do you need to use CT's over shunts? Is this a 3-phase application?

The maximum input level on the current channel is +/-31.25mV Peak, therefore a small burden would have to be chosen to not over range this input.

Regards,

Dlath

Dlath:

thanks for your reply

Because of the application we must use a CT

It is only a standard life-neutral and ground configuration (110V - 220V)

Adding a shunt current sensor will be more expensive and complicated

It will require some mechanical changes which are ussually very expensive

We already have a current trasnformer version with several customers

I can scale the CT output to match the ADE7933 input

I understand the redundancy of the isolation of both devices but it is simpler to use a current transformer

This device together with the ADE7978 will simplify our firmware implementation.

any notes on current transformer or any other device that you could suggest will be appreciated

Thank you

Fausto Bartar

Hi Fausto,

I understand better now, I can also suggest the ADE7923, this is a non-isolated version of the ADE7933 with the same footprint and slightly different package (without increased creepage).

As for connecting the CT, it is very similar to using a shunt with the addition of a burden resistor. The input still should look like the diagram in the data sheet, with the 1kOhm and 33nF anti-aliasing filter.

Then a burden resistor value needs to be chosen based on the maximum current expected, the turns ratio of the CT and the full scale inputs to the current channel.

Once this burden value is found, I would recommend a center-tapped burden like the diagram above.

Regards,

Dlath

Hi, my question is regarding center tapped configuration of burden resistor. Why this configuration is required? What if I use single burden resistor followed by anti aliasing filter?

 Regarding Current channel sensing through CT in ADE7953 

I replied here is this the same question?

Dave