Dear sir, kindly clarify is simple layman words,

I have a current transformer with 1 main meter outside the building and a control panel having 5 CT meters with black round coils inside the building. I want to know

A) when current pass through the Transformers, will the current be reduced or be the same and after that?

B) when current pass through the CT meters with black round coils, will the current be reduced or be the same?

C) in the above process will the reading of the main meter be same or different, from the total reading of all the 5 CT meters?

 

A & B Yes the current will be reduced by the CT Ratio.

The ratio is usually expressed like 50:5 or 50/5 which means, when there is 50 amps in the main wire going through the CT, there will be 5 Amps in the secondary. by the same logic if there is 27.5 amps in the primary there will be 2.75 Amps in the secondary.

Now here is a catch, sometimes there might be two or more turns of wire through the core of the transformer, this of course changes the ratio.

C This is too complicated to answer without a lot more information. we don't know how the CTs are wired or what they are wired to. If you are referring to a power usage meter, the ratio of the transformers should be taken into account, e.g., the meter reading would be multiplied by 10 in this case (500/5 = 10)

Hope this helps.

 

Roy,

The CT meters are used for commercial building, power usage of tenanted office space. As per your answer for "C", the reading of the main meter near the transformer will be different (more), with the total of all CT meter readings (less than the outside reading) with in the control panel. This is my understanding, am i correct?

Thanks.