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Old 7th January 2012, 12:54 AM   #1
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Smile current transformer

hi guys!i need current transformer calculate exemples!!
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Old 7th January 2012, 05:05 AM   #2
dtproff is offline dtproff  United States
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try here and see if that helps...

Practical Considerations Using GBI’s Current Sense Transformers

Tony
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Old 7th January 2012, 05:11 AM   #3
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what are you doing with a current transformer?

SAFETY WARNING

If you don't know how to use one, then don't. Current transformers are dangerous and can kill you. Do not allow the secondary to ever be open circuited while there is a chance current will flow through the primary winding. This will lead to very high, very dangerous voltages developing across the secondaries.
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Old 7th January 2012, 10:11 AM   #4
DF96 is offline DF96  England
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Student with assignment?
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Old 8th January 2012, 08:39 AM   #5
AJT is offline AJT  Philippines
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Quote:
Originally Posted by carlosgn View Post
hi guys!i need current transformer calculate exemples!!
it is all about turns ratio, a turns ratio of 1:1000 for example gives you a 1mA secondary when 1 ampere of current is flowing at the primary.......

that is what makes the current transformer dangerous, like mentioned already, the secondary is always shorted when not in use......

in some smaller CT's, the secondary is shunted by a two paralleled opposing polarity diodes to limit terminal voltage to 600millivolts.....
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Old 9th January 2012, 04:43 AM   #6
dtproff is offline dtproff  United States
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I will add one more thing to what Tony has said above. The key to the transformer is that it not saturate (using the turns ratio Ton talks about above). If you are using a standard ferrite core make care that the duty cycle stays below 50% and that the leakage is low enough that the saturation flux density does not cause core saturation using Ipk and Bmax with Lk (which is the leakage) for the Bsat calculation. The 50% duty cycle keeps the core from "flux walking" and the Bsat at temperature using Ipk and the leakage for the calculation, guarantees that the core will behave as expected over the full range of Ipk. I hope that helps.

I am making some assumptions that you understand magnetics and that you understand what I am talking about. If you do not understand, please ask and the members here will be more than happy to provide more detail.

Tony
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