Capacitive discharge battery tab spot welder

[Sully Kubillas]

Hi,

I am planning to build a capacitive discharge battery tab spot welder according to a schematic the image of which I am sending attached to this message. The question is: as the tyristor used in this project holds 50A, and I needed more than this, is it posible to wire two tyristors in paralell using the same control circuit? I should appreciate very much your help in this project.

Sully

 

[erikl]

... according to a schematic the image of which I am sending attached to this message.

Try once more, please!

 

[Sully Kubillas]

Hi,

Sorry, I was inable to sen the circuit image. I am giving here its URL:

**broken link removed**

This circuit uses a IR50RIA20 tyristor and I would like to know wether I can wire two tyristor in paralell to get more current. I have found out that with more current I can have better welding mainly on Li-Ion battery tab.
Many thanks for your attention to this matter.

Sully

 

[FvM]

The continuous current rating isn't of much interest in this application, you'll rather look for I²t and dI/dt.
Paralleling multiple SCRs is possible, but the gate current must be high enough to achieve low trigger delay and delay skew. Gate series resistors for equal current sharing are suggested.

 

[chuckey]

Q1 when on has Ib = 4.4mA, min Hfe = 80?, therefore Ic > 350 mA, but the continous Ic rating is 100 mA, and the pulsed is 350 mA. So I reckon holding the foot switch down is continous so I think the Q1 will cook, it needs an Ic limiting resistor somewhere.
Frank