Relay Introduction

Update date:2018-04-18 Source:MAXGE

Relay Introduction

  A relay is an electrical control device that is an electrical device that causes a predetermined step change in the controlled electrical quantity in an electrical output circuit when the change in the input quantity (driver amount) reaches a specified requirement. It has an interactive relationship between the control system (also known as the input loop) and the controlled system (also known as the output loop). Usually used in automated control circuits, it is actually an "automatic switch" that uses small currents to control high-current operation. Therefore, it plays a role in the circuit such as automatic adjustment, safety protection, and conversion circuit.

Relay: used to control the circuit, the current is small, there is no arc extinguishing device, it can be operated under the action of electricity or non-electricity. A relay often has several pairs of normally open/normally closed nodes, which can be used for different control loops, and its nodes Can not pass a large current, generally not used for power circuits.

Relay working principle


When the input amount (such as voltage, current, temperature, etc.) reaches the specified value, the relay turns on or off the controlled output circuit. Inputs can be divided into two categories: electrical quantities (such as current, voltage, frequency, power, etc.) and non-electrical quantities (such as temperature, pressure, and speed). Relays have the advantages of fast movement, stable operation, long service life, and small size. Widely used in power protection, automation, motion, remote control, measurement and communications devices.

Relay classification

There are many types of relays that can be categorized according to the principle of action, dimensions, protection features, contact load, product usage, etc.


First, according to the principle of action

1. Electromagnetic relay: An electrical relay that uses the circuit in the input circuit to work by the suction force generated between the core of the electromagnet and the armature.

2. Solid state relay: A relay that is separated from the input and output by an electronic component that performs its function without mechanical movement components.

3, temperature relay: When the outside temperature reaches a given value and the action of the relay.

4. Reed relay: The relay that opens, closes or changes the line by using the reed action that is sealed in the pipe and has double action of the electric reed and the armature magnetic circuit.

5, time relay: When adding or removing the input signal, the output part needs to delay or limit the time until the specified time to close or disconnect its controlled line relay.

6, high-frequency relays: used to switch high frequency, RF circuit and the relay with the minimum loss.

7. Polarization relay: A relay that acts with a combination of a polarized magnetic field and a control current through a magnetic field generated by a control coil. The direction of operation of the relay depends on the direction of the current flowing in the control coil.

8, wind speed relay: When the wind speed reaches a certain value, the controlled circuit will be turned on or off.

9, acceleration relay: When the acceleration of the moving object reaches the specified value, the controlled circuit will be turned on or off.

10, other types of relays: such as optical relays, acoustic relays, thermal relays, instrument relays, Hall effect relays, differential relays.


The role of the relay

The relay is an automatic switch element with isolation function. It is widely used in remote control, telemetry, communication, automatic control, electromechanical integration and power electronic equipment, and is one of the most important control elements. Relays generally have a sensing mechanism (input section) that can reflect a certain input variable (such as current, voltage, power, impedance, frequency, temperature, pressure, speed, light, etc.); there is the ability to achieve "through", " "Off" control of the implementation of the mechanism (output part); In the input and output parts of the relay, there is also the input of the coupling isolation, functional processing and the output part of the driving mechanism (drive part). As a control element, in summary, the relay has the following functions:

1, to expand the scope of control. For example, when the multi-contact relay control signal reaches a certain value, the multi-circuit may be switched, disconnected, and connected at the same time according to the different forms of the contact group.

2, zoom in. For example, sensitive relays, intermediate relays, etc., can control very large power circuits with a very small amount of control.

3, integrated signal. For example, when a plurality of control signals are input to a multi-winding relay in a prescribed form, after a comparison and synthesis, a predetermined control effect is achieved.

4, automatic, remote control, monitoring. For example, relays on an automatic device, together with other electrical appliances, can form a program control circuit for automated operation.

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