The working principle of electromagnetic relays, the role of electromagnetic relays

The working principle of the electromagnetic relay is to use the electromagnetic effect to control the mechanical contact to achieve the purpose of on-off, to energize the coil with the iron core, generate a magnetic field for the coil current, and adsorb the armature with the magnetic field to act on and off the contact, and the whole process is a process of "small current, magnetic, mechanical and large current".

Relays generally refer to electromagnetic relays, that is, mechanical actions.

The essence of the relay is to use one loop (generally a small current) to control the on/off of another circuit (generally a large current), and in this control process, the two circuits are generally isolated.

Electromagnetic relay, it has a coil, when the current is introduced into the circle, a magnetic field is generated around it, that is to say, it becomes an electromagnet, at its magnetic pole, there is an armature made of soft iron, as a moving contact, when the power is on, the street iron is attracted over, and the disconnection or closure of the static contact can be realized, so that the circuit can be controlled on and off, it is essentially a switch that can be automatically controlled. It can realize low voltage and weak current control and high voltage and strong current, and can also realize long-distance control and automatic control.

The working principle of the electromagnetic relay is that when the electromagnet is energized, the armature is sucked down to make D and E contact, and the working circuit is closed. When the electromagnet loses its magnetism when it is de-energized, the spring pulls the armature up and cuts off the working circuit.

An electromagnetic relay is an electronic control device, which has a control system and a controlled system. Usually used in automatic control circuits, it is actually a kind of "automatic switch" that uses a smaller current and a lower voltage to control a larger current and a higher voltage. Therefore, it plays the role of automatic auspicious adjustment, safety protection, and conversion circuit in the circuit.

It is widely used in automatic control, such as control circuits and communication fields in refrigerators, automobiles, elevators, machine tools. As long as a certain voltage is added to both ends of the coil, a certain electric coarse current will flow through the coil, resulting in an electromagnetic effect. The armature will overcome the tensile force of the return spring and attract to the iron core under the action of electromagnetic attraction, thereby driving the dynamic contact of the armature to engage with the static contact.

Other types

Thermal reed relay is a new type of thermal switch that uses thermal magnetic materials to detect and control temperature. It consists of a temperature-sensing magnetic ring, a constant magnetic ring, a reed switch, a thermally conductive mounting sheet, a plastic substrate and some other accessories. Thermal reed relays do not use coil excitation, but are driven by the magnetic force generated by the constant magnetic ring.

Whether the constant magnetic ring can provide magnetic force to the reed switch is determined by the temperature control characteristics of the thermosensitive magnetic ring.

The solid-state relay is a four-terminal device with two terminals as the input terminal and the other two terminals as the output terminal, and the intermediate isolation device is used to realize the electrical isolation of the input and output. Solid state relays can be divided into AC type and DC type according to the load power supply type, and can be divided into normally open type and normally closed type according to the switch type. According to the isolation type, it can be divided into hybrid type, transformer isolation type and optoelectronic isolation type, with the optoelectronic isolation type being the most.

The working principle of the electromagnetic relay is: when the coil is energized, the iron core is magnetized to generate a large enough electromagnetic force, suck the armature and drive the reed, so that the moving contact and the static contact are closed or separated, that is, the originally closed contact is disconnected, and the original broken contact is closed.

When the coil is powered off, the electromagnetic attraction disappears, the armature returns to its original position, and the moving and static contacts return to their original closed or separated state. In the application, as long as the circuit that needs to be controlled is connected to the contact, the relay can be used to achieve the purpose of control.

Electromagnetic relay is an electromechanical component that uses input signals (voltage, current) to generate electromagnetic force in the core of the electromagnet and attract armature, so that the contact action can be opened, closed or converted to control. Electromagnetic relays are widely used in aviation, aerospace, ships, home appliances and other fields, mainly to complete the functions of signal transmission, executive control, system power distribution, etc., and are one of the key electronic components in each system.

Selection of electromagnetic relays

1. Understand the necessary conditions: the power supply voltage of the control circuit, the maximum current that can be provided; voltage and current in the controlled circuit; How many sets of contacts and what form of contacts are required for the controlled circuit. When selecting relays, the power supply of the general control circuit can be used as the basis for selection.

The control circuit should be able to provide sufficient working current to the relay, otherwise the relay engagement is unstable.

2. Pay attention to the volume of the appliance: if the chain is used for general electrical appliances, in addition to considering the volume of the chassis, the small relay mainly considers the circuit board installation layout. For small electrical appliances, such as toys and remote control devices, ultra-small relay products should be selected.

The role of electromagnetic relays is described as follows:

A relay is a device that uses the on/off of low-voltage and weak-current circuits to indirectly control high-voltage and high-current circuits. Electromagnetic relay is a kind of switch that uses an electromagnet to control the working circuit.

When the protected component of the power system fails, the relay protection device should be able to automatically, quickly and selectively remove the faulty component from the power system, so as to ensure that the fault-free part quickly recovers normal operation and prevents the faulty component from continuing to suffer damage. reduce the scope of power outages; By the early 90s, the development, production and application of integrated circuits and large-scale integrated circuit protection were in a dominant position, and the era of computer relay protection for intelligent information processing is currently being studied.