Types and principles of relays, what is the principle of relays?

Classification and working principle of relays:

1) Electromagnetic relay: an electrical relay that works by using the suction force generated by the circuit in the input circuit between the electromagnet core and the armature.

2) Solid relay.

Refers to electronic components performing their functions without mechanical movement.

A kind of relay that isolates input and output.

3) Temperature relay: a relay that acts when the outside temperature reaches a given value.

4) Reed relay: a relay that uses the reed action of the reed sealed in the tube and has the dual role of electric shock reed and armature magnetic circuit to open, close or convert the line.

5) Time relay.

When the input signal is added or removed, the output part needs to be delayed or limited to a specified time before closing or disconnecting its controlled line relay.

6) High-frequency relay: a relay with minimal loss for switching high-frequency and RF lines.

7) Polarization relay: a relay that operates by the comprehensive action of the polarized magnetic field and the magnetic field generated by the control current through the control coil. The direction of action of the relay depends on the direction of the current flowing through the control coil.

8) Other types of relays: such as photorelays, acoustic relays, thermal relays.

Instrumentation relays, Hall effect relays, differential relays, etc.

Flash Relays, General Purpose Relays, Violet Relays, Light Relays, Charging Relays, Soldering Relays, High Power, Starting Relays, Light Relays, Preheating Relays, Horn Relays, Magnetic Latching Relays, Wiper Relays, High Voltage DC Contactors.

Thermal relay is a protective appliance used for overload protection of motors or other electrical equipment and electrical circuits.

In the actual operation of the motor, such as dragging the production machinery to work, if the machinery is abnormal or the circuit is abnormal, the motor will be overloaded, the speed of the motor will decrease, the current in the winding will increase, and the winding temperature of the motor will increase. If the overload current is not large and the overload time is short, and the motor windings do not exceed the allowable temperature rise, this overload is allowed. However, if the overload time is long and the overload current is large, the temperature rise of the motor winding will exceed the allowable value, which will make the motor winding age, shorten the service life of the motor, and even burn the motor winding in serious cases.

So, this overload is something that the motor can't withstand. Thermal relay is a protective appliance that uses the thermal effect principle of current to cut off the motor circuit when there is an overload that the motor cannot bear, and provides overload protection for the motor.

When the thermal relay is used to protect the motor from overload, the thermal element is connected in series with the stator winding of the motor, the normally closed contact of the thermal relay is connected in series in the control circuit of the electromagnetic coil of the AC contactor, and the setting current adjustment knob is adjusted so that the herringbone lever and the push rod are at an appropriate distance from each other. When the motor is working normally, the current through the thermal element is the rated current of the motor, the thermal element is heated, and the bimetal sheet is bent after being heated, so that the push rod is just in contact with the herringbone lever, and the herringbone lever cannot be pushed. The normally closed contact is closed, the AC contactor remains engaged, and the motor operates normally.

If the motor is overloaded, the current in the winding increases, the temperature of the bimetal sheet rises higher through the increase of the current in the thermal relay element, and the degree of bending increases, and the herringbone lever is promoted, and the herringbone lever pushes the normally closed contact, so that the contact is disconnected and the AC contactor coil circuit is disconnected, so that the contactor releases and cuts off the power supply of the motor, and the motor is stopped and protected.

It can be seen that thermal relays usually disconnect the control loop of the contactor directly to disconnect the main circuit.

1. Definition of relayRelay is an automatic control device that changes by leaps and bounds when the input quantity (electricity, magnetism, sound, light, heat) reaches a certain value. Second, the relay characteristics of the relay The input signal x of the relay continuously increases from zero to the action value xx when the armature begins to engage, and the output signal of the relay immediately jumps from y=0 to y=ym, that is, the normally open contact is from broken to on. Once the contact is closed, the input amount x continues to increase, and the output signal y will no longer change.

When the input quantity x drops from a value greater than xx to xf, the relay begins to release and the normally open contact opens (see Figure 1). We call this characteristic of the relay the relay the relay characteristic, also known as the input-output characteristic of the relay. The ratio of the release value xf to the action value xx is called the feedback coefficient, that is, the ratio of the control power pc output on the kf = xf xx contact to the minimum power p0 absorbed by the coil is called the control coefficient of the relay, that is, the classification of kc = pc p0 relay There are many classification methods for relays, which can be classified according to the principle of action, dimensions, protection characteristics, contact load, product use, etc.

1. According to the principle of action, it is divided into 1An electromagnetic relay is a relay that produces a predetermined response from the relative motion of mechanical parts under the action of the current in the input circuit. It includes DC electromagnetic relays, AC electromagnetic relays, magnetic latching relays, polarization relays, reed relays, energy-saving power relays.

1) DC electromagnetic relay: the electromagnetic relay in the input circuit with the control current of DC. (2) AC electromagnetic relay:

The control current in the input circuit.

Not only in automobiles, but also in the electronic circuits of any equipment and facilities, the role of relays is to use small voltage, or small current to control large current, or high voltage; However, it does not have the effect of increasing the current or voltage itself; What it does is what it does is what it does; Under the control of low current or low voltage, turn on (or disconnect) another pair (or pairs) of relatively large contacts, in the relay, the term is called normally closed and normally open; The purpose is to let the high current or high voltage drive the back load.

This is the main role of relays; Other Functions:

1. Isolation (mainly refers to strong and weak current, or AC and DC);

2. Protection; For example, when the display (high-end) displays the image, and when the output of the audio power amplifier is connected to the speaker (speaker), the relay is used;

3. Step-by-step conversion; In electronic circuits, sometimes the controlled voltage or current is relatively high or large, and the first-level relay cannot be completed, so it is necessary to use several levels of relay to make the transition.

The essence of the relay is to use a 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, its basic principle is to use the electromagnetic effect to control the mechanical contact to achieve the purpose of on-off, to electrify the coil with an iron core - the coil current to produce a magnetic field-magnetic field adsorption armature action on-off contact, the whole process is a process of "small current-magnetic-mechanical-large current".

Relay (English name: relay) is an electrical control device, which is an electrical appliance that makes a predetermined step change of the controlled quantity in the electrical output circuit when the change of the input quantity (excitation quantity) reaches the specified requirements.

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 automatic control circuits, it is actually a kind of "automatic switch" that uses a small current to control the operation of a large current.

Therefore, it plays the role of automatic adjustment, safety protection, and conversion circuit in the circuit.

Relay is an electrical appliance that turns on or off the control circuit according to the change of a certain input signal to realize automatic control and protection of the power drag system. The input signal can be the amount of electricity such as voltage and current, or it can be the non-amount of electricity such as speed, time, temperature and pressure.

The relay is generally not used to directly control the main electrical appliance with a strong signal current, but to control the main circuit through a contactor or other electrical appliances.

Relays include: 1. Current relays. Second, voltage relays. Third, thermal relays. Fourth, time relay. Fifth, speed relay.

There are many types of relays, and their working principles and structures are also different, but generally speaking, the relay is composed of three parts: the bearing mechanism, the intermediate mechanism and the actuator, the bearing mechanism is to reflect and access the input amount of the relay, and pass it to the intermediate mechanism, compare it with the rated setting value, when the setting value is reached (excessive or under), the intermediate mechanism will make the actuator produce output, so as to turn on or off the controlled circuit.

First of all, we have to talk about the structure of the relay, which is mainly composed of: iron core, coil, contact, etc. When the coil is fed into a power supply that matches the specifications, the iron core around it generates magnetism, attracting the normally open contacts to close and the circuit to turn on. The principle of electromagnetic induction is mainly used.

The function of the relay is to control the circuit, through which the function of controlling one or several signals with one control signal can be realized, and the control of start, stop, and linkage can be completed. The principle is an electrical control device, which is an electrical appliance that makes a predetermined step change of the controlled quantity in the electrical output circuit when the change of the input quantity meets the specified requirements.

Relays have been widely used in computer peripheral interface equipment, constant temperature systems, temperature regulation, electric furnace heating control, motor control, CNC machinery, remote control systems, industrial automation devices; Signal lights, dimming, flashers, lighting stage lighting control systems.

instrumentation, medical equipment, photocopiers, automatic washing machines; Automatic fire protection, security systems, and power capacitor transfer switches as power factor compensation for power factors in the power grid, etc., in addition, in the chemical industry, coal mines and other explosion-proof, moisture-proof, anti-corrosion occasions are widely used.

Electromagnetic relays are generally composed of iron cores, coils, armatures, contact reeds, etc. As long as a certain voltage is added to both ends of the first circle, a certain current will flow through the coil, resulting in an electromagnetic effect, and the armature will overcome the tensile force of the return spring under the action of electromagnetic force attraction to attract the core, thereby driving the dynamic contact of the armature to engage with the static contact (normally open contact).

Relays generally have an induction mechanism (input part) that can reflect certain input variables (such as current, voltage, power, impedance, frequency, temperature, pressure, speed, light, etc.); There is an actuator (output part) that can control the controlled circuit "on" and "off".

The permanent magnet is kept in a release state, and after the working voltage is added, the electromagnetic induction causes the armature and the permanent magnet to produce attraction and repulsion moments, resulting in downward motion, and finally reaching the state of engagement.

The working principle of the relay is to use the principle of electromagnetic induction, when the electromagnetic coil of the relay is energized, it will generate a magnetic field in the belt core, and this magnetic field will make the contact flip, so as to control the switching state of the circuit. Specifically, when the solenoid coil is energized, a magnetic field is generated in the iron core, and this magnetic field will attract or push the contacts open, causing the contacts to close or disconnect, thus controlling the circuit to turn on and off.