Burden for ACT-0750 CT and Arduino Due (3.3v)

Submitted by renza on Wed, 18/03/2015 - 14:16

Hi,

I have purchased some CTs from Continental Control Systems. Here's a link to the product page: www.ccontrolsys.com/w/ACT_Series_Split-Core_Current_Transformers

They come with a built in burden resistor, and put out 3.33v at the max rated current. Here is a list of the burden resistor values: http://www.ccontrolsys.com/w/ACT-0750_Internal_Burden_Resistance

Working backwards, I think these have CTs have 400 turns.

My question is, do I need to change the burden resistor, or will the 3.33v output of these be fine to use? If i work through the calculations, I end up with burden values exactly half of what is listed in the link above. So to come up with the correct burden value, I should simply add the same value resistor on the PCB in paralell with the CT to halve it's resistance.

Please let me know if i'm wrong.

edit: On second thoughts, I don't think I need to lower the burden resistance. If someone can confirm that would be much appreciated.

Edit - fixed link - BT

Re: Burden for ACT-0750 CT and Arduino Due (3.3v)

Submitted by Robert Wall on Wed, 18/03/2015 - 15:07.

You probably do need to add an external burden in parallel to lower the output voltage. Your 3.33 V output gives you 9.419 V peak-peak output. That will overload your input.

Re: Burden for ACT-0750 CT and Arduino Due (3.3v)

Submitted by renza on Wed, 18/03/2015 - 15:45.

~~Thanks for your reply Robert. I am using the Arduino Due so it has a 3.3v input.~~

~~I'm a little confused as to why the peak to peak output is 9.419V and not 4.709V. I might be missing something here!~~

~~So say for each of those burden values, I should aim to reduce the total burden resistance to a third of the built in resistor, is that correct?~~

edit: looks like I read the website wrong. its actually 0.333V at max current. They also have 1v models, which would probably be much more appropriate, I think. Can you confirm this?

Re: Burden for ACT-0750 CT and Arduino Due (3.3v)

Submitted by Robert Wall on Wed, 18/03/2015 - 15:59.

I take it that you want the large aperture because you are not in the UK?
Yes, the 1 V output is more suitable for the 3.3 V input range. (1 V rms = 1.414 V pk = 2.828 V pk-pk, always assuming you have a pure sine wave).
3.3 V input, by the time you've allowed for voltage and input tolerances, is nearer 3.2 V peak-peak available input range.

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