0
\$\begingroup\$

See the current transformer below. Primary to secondary turns ratio is 1000:1, and Test winding to secondary turns ratio is 1:1. The burden resistor across the secondary is 10 ohms. I'm trying to produce a 60Hz AC current for the test winding. This winding is only used when one wants to test the proper functioning of the secondary circuit. The resistance of both the test and secondary winding is 80 ohms.

enter image description here

As the ratio between test and secondary winding is 1:1, I would happy producing just 1 mA current. But I'm not sure how to do this from a 3.3V microcontroller.

The idea I have is to generate a square wave from the micro, and feed that to an amplifier as shown below. I think I don't need that amplifier though, because I only need 1 mA. The switch S4 is an analog switch to open the test winding when not testing. C8 is the coupling cap, and L3 would limit the current provided that it has higher impedance than the test coil.

Do you think this approach is okay? Can it be simplified by removing the amplifier? How do I choose the components to ensure 1 mA through the test coil?

enter image description here

\$\endgroup\$
2
  • 1
    \$\begingroup\$ What are the parameters of the test coil? If the thing has a make/model or better yet a datasheet, just say so. \$\endgroup\$
    – Justme
    Apr 5, 2020 at 7:53
  • \$\begingroup\$ Unfortunately, there’s no datasheet. I just have the drawing which says the numbers of turns and physical dimensions of the CT. I even had to measure the resistance with a meter. This is a very old CT. \$\endgroup\$
    – user115094
    Apr 5, 2020 at 14:03

0

Reset to default

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.