The On and Off control of any electrical equipment as shown in the below diagram is normally done through a mechanical switch that is normally made up of metallic contacts once in Off position the metallic contacts are isolated and in On position the metallic contacts are in contact position that allows the flow of electricty through them. To control the On and Off of such a switch remotly or through computer automation control is not possible and also the switch being mechanical in nature will suffer mechanical wear outes.

Solid state relay is a type of switch that dosent carry mechanical moving parts the electrical switching action is done through power semiconductors and insteard of human interface the switch can be operated by small DC control voltages as shown in the diagram below this DC voltage can be from any control equipment like computers or signals from inductrial control panels etc.

Solid state relays are used in many applications that involves control of high voltage AC using low voltage DC( control voltage) without the use of mechanical switches, some of the applications involve ON OFF control of lights, motors, water heaters, fans, advertisement lighting and AC power ON OFF to industrial machines. This solid state relay can also be used in places where regular periodic ON OFF operation of electrical equipments is required

Solid state relays are useful in almost all those type of electrical systems where automation control is required being solid in nature and with complete electronic control the life of such device is many more times longer as compared to mechanical relays.

Advantages:

• The operations is controlled by Semiconductors.
• Noiseless operation
• Protect the equipment form high voltage and surge.