I am using 2 CR8401-1000-A current transformers in opposite polarity to sense current on either side of a load. The Idea is that when the load is not in failure mode that the sensed current waveforms will be exact opposites and when "added together" will cancel each other out. In failure mode, or ground fault, there will be an alternate path for current. The wave currents will no longer cancel and yield a net current. This signal is amplified by an op amp circuit, and rectified by a precision full wave rectifier. The now DC signal is sent to an ADC. A micro controller coupled to the ADC will throw a breaker at programmed current thresholds. My question is this, can the 2 current transformers be connected in reverse polarity in parallel directly, or should there be a buffer circuit between them?

 

I am using 2 CR8401-1000-A current transformers in opposite polarity to sense current on either side of a load. The Idea is that when the load is not in failure mode that the sensed current waveforms will be exact opposites and when "added together" will cancel each other out. In failure mode, or ground fault, there will be an alternate path for current. The wave currents will no longer cancel and yield a net current. This signal is amplified by an op amp circuit, and rectified by a precision full wave rectifier. The now DC signal is sent to an ADC. A micro controller coupled to the ADC will throw a breaker at programmed current thresholds. My question is this, can the 2 current transformers be connected in reverse polarity in parallel directly, or should there be a buffer circuit between them?

What have you found when you pulled apart a commercially available GFI.

 

Just run both wires through the same current transformer so that their current flows are in a normally oppong flow pattern.

You will get the same normal current flow cancellation effect you are looking for while using less parts.

 

Just run both wires through the same current transformer so that their current flows are in a normally oppong flow pattern.

You will get the same normal current flow cancellation effect you are looking for while using less parts.

I know that what you are saying should work, but it does not seem to.

 

What have you found when you pulled apart a commercially available GFI.

I haven't officially taken one apart, but Google says it is two opposing current transformers powering two relay windings

 

What have you found when you pulled apart a commercially available GFI.

I haven't officially taken one apart, but Google says it is two opposing current transformers relay windings.

 

Just run both wires through the same current transformer so that their current flows are in a normally oppong flow pattern.

You will get the same normal current flow cancellation effect you are looking for while using less parts.

Just run both wires through the same current transformer so that their current flows are in a normally oppong flow pattern.

You will get the same normal current flow cancellation effect you are looking for while using less parts.

My current design with a single wire through one transformer yields 250 mv/ma after amplification. The micro controller runs a digital display working just like an ammeter, so you can easily see the output. My next baby step was powering a light bulb on 12VAC (approx .42 amps) running both wires through one transformer. The resultant output after amplification was 5 VAC, far from canceling out.This threw me for a loop. I am amplifying something that shouldn't be there.