Hi. Can someone explain why a snubber is needed for thyristor circuits?

All I understand is that when the thyristor is switched off the capacitor clamps the voltage so that the thyristor does not relatch through avalanche. Is this right?

Also is a snubber needed for both turn on and turn off?

 

Hello,

You already asked here:
http://forum.allaboutcircuits.com/showthread.php?t=38100

Here are extra links of the EDUCYPEDIA with links on snubber circuits adn transient suppression :
http://www.educypedia.be/electronics/powerelectronics.htm
http://www.educypedia.be/electronics/Transientsuppression.htm

Bertus