Relay role is used to control the circuit, through the relay can be realized with a control signal to control another way or several signals, complete the start, stop, linkage and other control. The principle is an electrical control device, is when the change of the input quantity reaches the specified requirements, in the electrical output circuit so that the controlled quantity occurs a predetermined step change of a kind of electrical appliances.
Relays have been widely used in computer peripheral interface devices, constant temperature system, temperature control, furnace heating control, motor control, CNC machinery, remote control systems, industrial automation devices; signal lamps, dimming, blinker, lighting stage lighting control system.
Instrumentation, medical equipment, photocopiers, automatic washing machines; automatic fire-fighting, security systems, as well as power factor compensation as the grid power capacitor switch and so on, in addition to the chemical industry, coal mines and other explosion-proof, moisture-proof, corrosion-resistant occasions have a large number of uses.
Electromagnetic relays are generally composed of an iron core, coil, armature, contact reeds and so on. As long as the coil ends plus a certain voltage, the coil will flow through a certain current, resulting in an electromagnetic effect, the armature will be attracted in the electromagnetic force under the action of overcoming the return of the spring tension suction to the iron core, thus driving the armature of the dynamic contacts and static contacts (normally open contacts) suction.
Relays generally have a certain input variables (such as current, voltage, power, impedance, frequency, temperature, pressure, speed, light, etc.) can reflect the sensing mechanism (input part); can be controlled circuit to achieve the "on", "off" control The actuator (output part).