SCR or THYRISTOR will have three regions of operations based on the mode in which the device is connected in the circuit.

Reverse blocking region: When the CATHODE of the thyristor is made positive with respect to the anode and no gate signal is applied. In this region scr exhibits the reverse blocking characteristics similar to diode.

Forward blocking region: In this region the anode of the thyristor is made positive with respect to the cathode and no gate signal is applied to the thyristor. A small leakage current flow in this mode of operation of the thyristor.

Forward conduction region: when the forward VOLTAGE applied between the anode and cathode increases at particular break over voltage avalanche breakdown takes place and thyristor starts CONDUCTING current in forward direction. By this type of TRIGGERING the device damages the scr. Hence a gate signal is applied before the forward break over voltage to trigger the scr.

SCR or thyristor will have three regions of operations based on the mode in which the device is connected in the circuit.

Reverse blocking region: When the cathode of the thyristor is made positive with respect to the anode and no gate signal is applied. In this region scr exhibits the reverse blocking characteristics similar to diode.

Forward blocking region: In this region the anode of the thyristor is made positive with respect to the cathode and no gate signal is applied to the thyristor. A small leakage current flow in this mode of operation of the thyristor.

Forward conduction region: when the forward voltage applied between the anode and cathode increases at particular break over voltage avalanche breakdown takes place and thyristor starts conducting current in forward direction. By this type of triggering the device damages the scr. Hence a gate signal is applied before the forward break over voltage to trigger the scr.