Thyristors (SCR, GTO, MCT)

Thyristors are a family of semiconductor devices widely used in power electronic circuits such as SCR (silicon controlled rectifier), DIAC (diode on alternating current), TRIAC (triode on alternating current).

SCR:

 A silicon controlled rectifier or semiconductor controlled rectifier is a four-layer solid-state current control device.

SCRs are unidirectional devices (i.e. they can conduct current in only one direction)

There are three modes of operation for an SCR depending on the polarization given to it:

1. Direct lock mode (off state)

2. Direct driving mode (on state)

3. Reverse lock mode (off state)

Applications

SCRs are primarily used in devices where high power is controlled, possibly in conjunction with high voltage.

SCRs and similar devices are used for high-power AC rectification in high-voltage DC power transmission.