How do we design a toroidal current transformer?
You need to know:
To eliminate the influence of the primary
resistance r1 and the leaking impedance X12 betwen the windings
the secondary winding has to be wound first., inside!
Before you start to run the program you need to determine the following parameters:
If you want to design ONE-TURN
toroidal current transformer then :
Now you are calculating the max. allowed magnetizing currents:
Ifea = c%*I2 /100 and Ifer = I2*tg(Alfa)
Normally the current transformer works in the linear part of the magnetic curve , in rolling direction:
The next condition uses the active losses in the
- l => average core length
Creating the input in the design program
Note that that the Toroidal Transformers Program supports the input of a power transformer. You have to know the input voltage, the output voltage and the output current. In order to run the program you have to set primary vo÷tage equel to the secondary voltage. In the end phase of the design you will come to the Test mode wherw you can manipulate the number of turns and the input voltage by hand . So you can similulate the IS operation mode of your current transformer!
To limit the inflence of the temperature in the value of the
voltage drop on the resistance r2 it is recommended to use the
criterion of the design the regulation:
ps-oRDER = 2 =>SsECONDARY WINDING INSIDE!
In the next step you need to create the core 50x80/30mm
Run the the program and open the Test mode.
Now you can change the turns of the primary winding W1=1 and the secondary winding W2 = 40 and vary the primary voltage in order to get I1=200A. The secondary current has to be I2>4.95A and the Angle<1░:
Now increase the the value of the input field U_input in order to get I1=200A and I2>4.95A or I2=4.95A and I1<200A.. In both cases the phase betweeb the input and output current has to be <1░.
Finally here is the result of this design
If you want to vary the input voltage you have to vary the primary voltage U_input. At U_input=1 the primary voltage is 2V
In the following table you can find the values of p and K for the steels which are supported in the Rale Design System