Leakage current measurement.

Thread Starter

moonlystar1111

Joined Feb 1, 2024
57
I(L1) = I(L3) - I(R4)
I changed the divide to minus. It looks like L1 has the current of R4+R2 while L3 has the current of R2.

It is much better if you include the LTspice file.

ps
Are you working on "Ground Fault Protection"? In that case the transformer(s) are wrong.
I(L1) = I(L3) - I(R4). Yes, I think this equation is correct.
Yes I'm working on ground fault protection. And I need a current transformer whose primary is both hot and neutral wire. I want to draw ct in ltspice but I'm not getting to make one. I need help in that.
 

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Last edited:

ronsimpson

Joined Oct 7, 2019
3,045
Added a ground on one of the R3 just so I can see it easier. (not needed)
Changed the CT to act correctly. Reversed phasing of L3! Put L1 and L3 on the same core.
When current flows in R1 it passes forward and backward through the CT and cancels out. So the CT does not see it.
When current flows in R2 it appears in L2 and thus R3 (via the turn ratio)
I would make R3, 100 ohms to get more voltage.
I changed the turns ration mostly because I have many 100:1 CT transformers.
1708716929613.png
 

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Thread Starter

moonlystar1111

Joined Feb 1, 2024
57
Added a ground on one of the R3 just so I can see it easier. (not needed)
Changed the CT to act correctly. Reversed phasing of L3! Put L1 and L3 on the same core.
When current flows in R1 it passes forward and backward through the CT and cancels out. So the CT does not see it.
When current flows in R2 it appears in L2 and thus R3 (via the turn ratio)
I would make R3, 100 ohms to get more voltage.
I changed the turns ration mostly because I have many 100:1 CT transformers.
View attachment 316005
I tried doing so and it worked. Just got my output.
 
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