How Does a Relay Operate
A relay is a switch that opens and closes a circuit electromechanically. It is widely used in a wide range of applications including power generation, transmission, control systems, telecommunication and more. Relays are primarily based on electromagnets but they can also use other operating principles like solid state. Relays are typically designed to switch AC or DC loads and they must be able to quench the electrical arc that forms when the contacts open.
The main components of a relay are the coil, armature, spring and yoke. The armature is the moving arm of the switch and it makes or breaks contact with the yoke when energized. The yoke is a piece of metal that connects the movable arm to the rest of the switch.
Once the yoke has been connected to the movable arm, a magnetic field is created around it. The magnetic field attracts the movable arm and moves it to the position that is opposite of its initial position. The armature will then make or break the contact between the yoke and fixed contacts depending on its construction. When the coil is de-energized, a force, usually half as strong as the magnetic field, will return the armature to its original position.
Relays come in different designs and sizes but they all operate in a similar way. The input part of the relay can reflect certain input variables like current, voltage, power, impedance, frequency, temperature, speed etc and there is an output part that realizes the “on” or “off” control of the external circuit.
A relay works by passing a low-power control signal from the power source through its switching mechanism to activate its coil and then connecting its output to the external circuit. A relay can have several contacts that are named as normally open (NO),normally closed (NC) and common (COM). The NO terminals are connected to the armature or the common terminal and the NC terminals are connected to the coil.
When a relay is powered, a copper coil winding around its iron core becomes energized and starts creating a magnetic field. The armature of the relay is then attracted to the magnetic field and moves to its desired position. As the armature moves, it closes or opens the contacts which then connect the relay’s power source to the external circuit.
The armature is returned to its original position by a spring or a permanent magnet. Relays can have many different combinations of poles and throws that determine how much current they can carry when energized. For example, a single-pole relay can only carry current through one isolated circuit while a double-throw relay can control two.
The yoke and the contact of a relay can be made from different materials, but they must be selected to match the requirements of the load that is being switched. In addition, the contacts must be rated for AC or DC voltage and they should have minimal contact resistance and wear. 중계