The terminology “Poles and throws” is also applicable for relay.

Relay Contact TypesĪs we have seen that relay is a switch. Solid state relays will have sensing element to sense the input voltage and switches the output using opto-coupling. exactly to opposite to the above shown relay. There are also such relays, whose contacts are initially closed and opened when there is supply i.e. When the supply is removed it retrieves back to the original position.When the coil is applied with DC current, it starts attracting the contact as shown.In the relay, Copper coil and the iron core acts as electromagnet.A switch is used to apply DC current to the load. Above image shows working of the relay.When the electromagnet is applied with some current, it induces a magnetic field around it.Relay works on the principle of electromagnetic induction.The following animation shows a simplified working of a relay. Such mechanisms include electronic circuit arrangement or shaded coil mechanism. So, AC relays are constructed with special mechanism such that continuous magnetism is provided in order to avoid above problem. In case of AC relays, for every current zero position, the relay coil gets demagnetized and hence there would be a chance of continues breaking of the circuit. We can use a Relay either in a AC circuit or a DC Circuit. These contacts are named as normally open (NO),normally closed(NC) and common(COM) contacts. Another contact called common contact is present in order to connect the switching points. Generally two more contacts will be present, called as switching points to connect high ampere load.

The two ends of the coil are connected to two pins of the relay as shown. Although many different types of relay were present, their working is same.Įvery electromechanical relay consists of an consists of anĮlectromagnet is constructed by wounding a copper coil on a metal core. Let us see the internal parts of this relay before knowing about it working. Electromechanical relays are frequently used. Relays can be of different types like electromechanical, solid state. But instead of a manual operation, a relay uses an electrical signal to control an electromagnet, which in turn connects or disconnects another circuit. While we use normal switches to close or open a circuit manually, a Relay is also a switch that connects or disconnects two circuits. A Relay is a simple electromechanical switch.

Common pin relay