Solving SCR Circuit Problem - EE Student Seeking Help

[tanky322]

I came across a circuit online to vary the 220V input into a welder. This is done to control the amount of current entering the piece being welded, using a foot pedal. The circuit has worked for many people.

I built the circuit, but it doesn't work. R2 blew when I would crank the pot up, and there was no current entering the welder. I don't know if the SCR fired or not, but it wouldn't weld or make a spark what so ever.

My initial thoughts are that the circuit was designed for a particular type of SCR, and mine isn't compatible.

Also, I am an EE student but I am just starting out, I have some circuit theory under my belt, but I am not sure on what to use as a voltage in this circuit, as its all part of the 220V line.

Can anyone help me out?

Sorry for the size of the pictures, but I wanted to keep the detail.

Thank you!

 

[capnahab]

In my lifetime I have worked on all kinds of complicated equipment, including welders and they are the worst because they are a basic power supply.

 

[ravenprp]

Hello,

Thank you for reaching out for help with your SCR circuit problem. It sounds like you have put a lot of effort into building this circuit and it can be frustrating when it doesn't work as expected. Let's see if we can troubleshoot and find a solution.

Firstly, it is important to make sure that all components in the circuit are compatible and able to handle the voltage and current levels involved. It is possible that the SCR you are using is not suitable for this circuit. I would recommend checking the datasheet of the SCR and comparing it to the one used in the original design. This can help determine if it is the cause of the issue.

Another potential issue could be the potentiometer (R2) being used. Make sure it has the correct resistance rating and is able to handle the current flowing through it. If it is not suitable, it can easily blow when the pot is cranked up.

In terms of the voltage to use in the circuit, you can use a step-down transformer to lower the 220V input to a more manageable level. This can also help protect your components and prevent any accidents.

Lastly, I would recommend double-checking all connections and making sure they are correct and secure. Sometimes a simple mistake can cause a circuit to not work.

If you are still having trouble, I suggest seeking help from a more experienced individual, such as a professor or a professional in the field. They can offer valuable insights and guide you in the right direction.

I hope this helps and wish you the best of luck in solving your SCR circuit problem. Keep learning and don't be discouraged, as troubleshooting is an important skill for any engineer.