I am trying to model a thyristor DC switch but I am having problems with properly turning "ON" the SCR that is used as the switch. I am using a 2N1595 SCR and I've looked at its datasheet and it seems like the parameters I have for my gate current source and gate resistance should trigger the SCR. However, it seems the thyristor continues blocking the current in the circuit even after the gate current gets applied. How can I fix this?
It looks like your voltage source is backwards for the gate drive to the SCR, the gate voltage for an SCR needs to positive, you are giving it a negative voltage. Here is a good reference for SCR's
Your gate voltage is inverted. Also, you should use a higher voltage in the gate as per the datasheet it should be, at least 3V (10V maximum.) The gate current should be limited to 0.1A.
Note that the main power voltage is 50. According to the datasheet that is the maximum forward blocking voltage. This means that in a real component, the SCR could trigger without gate pulse.