# Current Transformer - how to calculate burden resistance

1. ## Current Transformer

Hi
How to calculate burden resistance required for CT of ratio 50:5, is thr any formula for it??

Thanks

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2. ## Re: Current Transformer

Usually this is simply chosen so that for the given primary current you get the required voltage.
Say you need 1V at 1A with your transformer. The secondary current is going to be 0.1A when the primary current is 1A. So R=1V/0.1A=10 ohm.

There are other things to consider, but you are not designing the current transformer, you are just using it. So that's pretty much it.

3. ## Current Transformer

Thanks VVV
Can help u tell me Which rectifier will be better to convert o/p of this CT to DC vtg. normal bridge rectifier or any special one.

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4. ## Re: Current Transformer

Yes a normal rectifier can do the job, even 1N4148 can do it.

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5. ## Re: Current Transformer

A single rectifier will do. Generally, the 1N4148 is a good choice. Just make sure you do not exceed the peak current, or choose a different diode. A fast diode is always a better choice.

6. ## Re: Current Transformer

I hope that you know that you may have to factor in the diode drop to get required accuracy.
1N4148 has upto max of 1V.
Maybe some further reading on precision rectifiers,could be useful.

7. ## Current Transformer

can you suggest me any precision amplifier for this application???

8. ## Re: Current Transformer

Op amp is often used to make a precision rectifier, you can refer to any book/datasheet/application notes of op-amp.

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9. ## Re: Current Transformer - how to calculate burden resistance

hi

formula

ADC maximum input voltage = (IMAX/ct ratio)*burden resistor

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