The SCR was developed by a team of power engineers led by Gordon Hall and commercialized by Frank W. ... SCRs are unidirectional devices (i.e. can conduct current only in one direction) as opposed to TRIACs, which are bidirectional (i.e. charge carriers can flow through them in either direction).

Why SCR Cannot be used as a bidirectional switch?

Why SCR cannot be used as a bidirectional switch.

SCR can do conduction only when anode is positive with respect to cathode with proper gate current. Therefore, SCR operates only in one direction and cannot be used as bidirectional switch.

What is the working principle of SCR?

The basic working principle in the SCR is that as the triggering or the biasing is applied at the terminal gate then the conduction begins. As it is a unidirectional device the current will be in a single direction.