multiple windings in amp clamp


In the past weeks I've been building a monitoring system for my wind generator. Since two days it is set up and running fine! But I have a question referring to the SCT-013-000 Current Transformer. I've installed it around the + wire that connects the invertor to the grid.

Since I got the intention by reading the report from Robert Wall, the accuracy will be higher if there are more windings running through the clamp meter (especially with low currents running through it), I now have the wire running 12 times through the clamp. 

My question: Is it true the accuracy will go up, and is it still save? I don't expect the amount of ampere will go higher than 3, so 3 x 12 = 36 ampere. This is way below the max of 150 ampere the clamp is able to handle. Am I right here, or do I misunderstand?

Kind regards, Thijs

Robert Wall's picture

Re: multiple windings in amp clamp

No, you do not misunderstand. You will read a true current of 3 A as 36 A, therefore you must alter your current calibration constant in the emonTx to bring the current back to the correct value. What you now have is not a 100 A : 50 mA current transformer, but a 8.333 A : 50 mA one. The turns ratio is nominally 166.667. I cannot remember which version of emonTx you have, you can find the calculations for the coefficient here.

(BTW, your problem with Ethercard library appears to be that over the years, the library has grown bigger and there is not enough memory in the NanodeRF to run today's version.)

Thijs's picture

Re: multiple windings in amp clamp

Hi Robert,

Thanks again! I multiplied the outcome of the input in emoncms by 0.08333. So in that case I got the right feed for my graphs. 

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