Describe the operation of SCR.(4 marks)craft1 electrical June/July 2020

An SCR (silicon controlled rectifier) is a type of three-terminal semiconductor device that acts as a switch and can be used to control the flow of current in a circuit. The operation of an SCR is based on the ability of the device to be turned on (conducting) or off (non-conducting) by the application of a voltage to its gate terminal. When an SCR is turned off, it acts like an open circuit and does not allow current to flow through it. When it is turned on, it acts like a closed circuit and allows current to flow through it.

The main characteristics of SCR operation are:

1. Forward blocking: When an SCR is in the forward blocking state (off), a voltage applied to the anode and cathode will not cause current to flow through the device.
2. Forward conduction: When an SCR is in the forward conduction state (on), a voltage applied to the anode and cathode will cause current to flow through the device. The SCR will remain in the conduction state as long as the voltage is applied and will not turn off until the current through the device falls below a certain level (the “holding current”).
3. Reverse blocking: When an SCR is in the reverse blocking state (off), a voltage applied to the cathode and anode will not cause current to flow through the device.
4. Reverse conduction: When an SCR is in the reverse conduction state (on), a voltage applied to the cathode and anode will