Current transformers

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kspifldorf

kspifldorf

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I have a 60:5 CT going to a 3PH unbalance detector which will only read from 1-5 amps. The CT will be reading anywhere from 150-180 amps. In order to tame the secondary down below 5 amp to prevent damage to the detector, I will need to reverse wind the secondary back through the CT. I need a way to test the output without damaging my DMM. Extremely confused.:confused:
 
Thanks Fellers. I was trying to impliment the parts that I did not buy. Just gonna have to back up and punt. Why are talented people so busy...............
They're fixing the problems made by people who have time. Thanks Again. KEG:D
 
You will saturate the CT and therefore most likely end up with non-accuarate measurements. A CT should be sized anyware from 1.5 to 2.5 times the normal expected current you are trying to measure. If you know the CT manufacturer your going to use, get the CT secondary excitation characteristics curves from them.
 
Adjusting CT ratio with secondary turns.

Adjusting CT ratio with secondary turns.

kspifldorf said:
In order to tame the secondary down below 5 amp to prevent damage to the detector, I will need to reverse wind the secondary back through the CT. :confused:
Click to expand...

24 evenly spaced turns of the ct secondary wire through the 60:5 ct would give 5 A output for 180 amps input. 5 A = [180 - (24x5)] x 5/60.

This might work if there is room in the donut for the 24 turns, the turns are evenly spaced, the CT doesn't saturate, the CT core's thermal limits are not exceeded, and other issues don't arise. If the initial 120 A current saturates the CT, there won't be enough secondary current in the 24 turns needed to counteract the primary current's flux.

Also the errors from the modified CT will pobably trip your imbalance monitor any way.

Bottom lione: get different CT's.
 
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