CURRENT TRANSFORMER 30A / 5A Interfacing with AVR Atmega32 ADC

atmegaavr

I am trying to Calculate Current of 1HP Motor uses with Motor Starter Box. Initially when Motor is started i can see current shoots upto 20-22A on analogue meter in starter box.

I want to measure this Current Continously while the motor is in operation.

For that purpose i have purchased 30A / 5A (CT) (12 Turns wound on CT) AC Current Transformer 30/5 A (Two turn Primary)

on 30A AC load it will provide me 5A AC output on secondary (CT output). Burden Capacity is 2.5VA. I am confused with burden resistor calculator and how can i interface CT with ADC of atemga32.

Please can anyone help.

Best Answer

Most current transformer use a resister in parallel to convert the current into voltage. This is because most ADC's are Voltage ADC's. The resistor should be chosen such that the peak expected current produces the maximum voltage that your ADC can read. There is one caveat. Your transformer says that it can/should only dissipate 2.5VA (watts) into the load.

Calculation for the resistor is: V_adc_max/I_current_transformer_max = Resistance. Also 2.5 >= (I_current_transformer_max)^2 * Resistance.