- 19th November 2008, 18:01 #1

- Join Date
- Nov 2008
- Location
- India
- Posts
- 18
- Helped
- 0 / 0
- Points
- 1,225
- Level
- 7

## Current Transformer

Hi

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

Thanks

- 19th November 2008, 18:21 #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.

- 19th November 2008, 18:21

- 19th November 2008, 18:27 #3

- Join Date
- Nov 2008
- Location
- India
- Posts
- 18
- Helped
- 0 / 0
- Points
- 1,225
- Level
- 7

## 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.

- 19th November 2008, 18:27

- 20th November 2008, 08:59 #4

- Join Date
- Jul 2007
- Location
- Some Where In Heaven
- Posts
- 415
- Helped
- 95 / 95
- Points
- 7,503
- Level
- 20

## Re: Current Transformer

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

- 20th November 2008, 08:59

- 20th November 2008, 18:34 #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.

- 20th November 2008, 19:11 #6

- Join Date
- Feb 2007
- Posts
- 78
- Helped
- 2 / 2
- Points
- 2,257
- Level
- 11

## 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.

- 21st November 2008, 13:22 #7

- Join Date
- Nov 2008
- Location
- India
- Posts
- 18
- Helped
- 0 / 0
- Points
- 1,225
- Level
- 7

## Current Transformer

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

- 26th November 2008, 05:20 #8

- Join Date
- Sep 2006
- Posts
- 440
- Helped
- 44 / 44
- Points
- 3,085
- Level
- 13

## 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.

- 11th December 2011, 03:50 #9

- Join Date
- Feb 2008
- Posts
- 12
- Helped
- 0 / 0
- Points
- 1,033
- Level
- 7

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

hi

formula

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