Here I have attached my ckt for my application. My application is Motor protection Relay. Based on Current sense of 3 CT tripping of relay will occur. Tripping might due to under/over/SC/Locked rotor Etc. Now I am facing in selection of CT and interfacing with Arduino Un0.

I know HP rating and its max current measurement range.

  1. How to Select CT for my application based on Current measurement range
  2. How Burden resistor calculated.
  3. How Size of CT can be calculated.
  4. How to judge max supply voltage supplied to Arduino
  5. Type of CT to be used protection class CT or Normal CT
  6. How to calculate Max Current level can read through CT. it will be mentioned in datasheet. what it will do when it cross rated current? means when it attain saturation if I use above circuit what is effect on Arduino Uno board.
  7. How burden VA calculated here.

I have researched and got one of application where they using AC AC1030 datasheet

Ip=30A I max=75A
 turns ratio: 1000:1
 supply voltage = 220VAC 
min power continuous CT can sense = 220X30 = 6.6 kW 
Max power sense for short period=220*75=16.5 kW

burden resistor= 2.5/(42/1000)=59.5ohm R1=R2=100kohm resistor.

Is it correct? What are other care I need to consider while taking hardware design?

Application CKt Current _range & Motor Range

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