Technical Guide for General-purpose Relays CSM_GeneralRelay_TG_E_3_1 Overview of General-purpose Relays ■ What Are Relays? To get an idea of what relays are, think of a children's athletic carnival. ■ Structure and Principle of Relays A relay consists of an electromagnet that receives an electric signal and converts it to a mechanical action and a switch that open and closes the electric circuit. Electric signal received and converted into an action. Switch for controlling the flow of electricity turns ON or OFF. Action transferred. Output The baton is the signal. Pressed. Action transferred. Contact Attraction Input Input Output Coil Armature Switch Electromagnet Little A holds on tightly to the baton and passes it to the Big B. This is a relay. Now lets look at a more technical example. Think of turning on a television with a remote control. I want to watch TV. Electromagnetic Switch section section Schematic Diagram Showing the Principle of Relays General Relays Signal Television Pressing the remote control power switch creates a signal. Infrared signal received. Relay Electric signal Lamp Contact Contact segment TV Moving contact Fixed contact Armature Remote control S1 Attraction Electric energy Electromagnet B A Release spring 100-VAC power supply Operating coil Yoke Iron core i (current) Internal circuit Switch Load power supply Coil power supply External circuit Principle of Operation The desire to watch television Remote control is converted to a Electric signal signal. Electric energy is applied to the television when it receives the electric signal. Input Output A relay receives electric signals and controls another flow of electricity. In this example, we will turn ON a lamp using switch S1 and a relay. 1. 2. 3. 4. Press S1 to turn it ON. Current i flows to the operating coil and magnetizes the core. The armature is drawn to the core by the electromagnetic force. When the armature reaches the core, the moving and fixed contacts make contact and the lamp lights. 5. When S1 is released to turn it OFF, current no longer flows to the operating coil, the electromagnetic force no longer exists, and the armature returns to its original position by the force of the release spring. 6. When the armature has returned to its original state, the contacts become separated and the lamp turns OFF. 1