When the input (such as voltage, current, temperature, etc.) reaches the specified value, the relay is controlled by the output circuit on or off.
The input quantities can be divided into electrical quantities (such as current, voltage, frequency, power, etc.) and non-electrical quantities (such as temperature, pressure, speed, etc.) two categories.
Relays have the advantages of fast action, stable operation, long service life and small size. Widely used in electric power protection, automation, motion, remote control, measurement and communication devices.
Two, different relays principle characteristics of electromagnetic relays electromagnetic relay electromagnetic relay is generally composed of 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, thus generating an electromagnetic effect, the armature will be attracted in the electromagnetic force under the action of overcoming the return spring tension suction to the iron core, thus driving the armature's moving contacts and static contacts (normally open contacts) suction. When the coil is powered off, the electromagnetic suction also disappears, the armature will return to its original position under the reaction force of the spring, so that the movable contact and the original static contact (normally closed contact) release. This suction, release, so as to achieve the purpose of conduction in the circuit, cut off. For the relay "normally open, normally closed" contacts, can be distinguished in this way: the relay coil is not energized in the disconnected state of the static contacts, known as "normally open contacts"; in the on state of the static contacts known as "normally closed contacts The static contact in the on state is called "normally closed contact". Relays generally have two circuits, for low-voltage control circuits and high-voltage operating circuits.
Solid state relay (SSR) solid state relay is a two terminals for the input, the other two terminals for the output of the four-terminal device, the middle of the use of isolation devices to achieve electrical isolation of input and output.
Solid state relays can be divided into AC and DC types according to the type of load power. According to the switch type can be divided into normally open and normally closed type. According to the isolation type can be divided into hybrid, transformer isolation type and photoelectric isolation type, to photoelectric isolation type for the most.
Thermal Reed RelayThermal Reed Relay is a new type of thermal switch that utilizes thermal magnetic material to detect and control temperature. It consists of a temperature-sensitive magnetic ring, constant magnetic ring, reed switch, thermally conductive mounting piece, plastic backing and some other accessories. The thermal reed relay does not use coil excitation, but the magnetic force generated by the constant magnetic ring to drive the switch action. The ability of the constant magnetic ring to provide magnetic force to the reed switch is determined by the temperature control characteristics of the temperature-sensitive magnetic ring.
Reed RelayThe Reed Relay is a coil sensing device that uses a coil to generate a magnetic field to actuate the reed switch. Therefore, reed relays are characterized by small size, light weight, fast response time, and short tripping time.
When a piece of ferromagnetic metal or other magnetically conductive material and its proximity, the action occurs, open or close the circuit. Composed of permanent magnets and reed switches. Permanent magnet, reed switch is fixed in a non-conductive and non-magnetic bracket. The axis of the north and south poles of the permanent magnet should coincide or almost coincide with the axis of the reed switch. Adjust the distance between the permanent magnet and the reed switch from far to near, and fix the position of the magnet when the reed switch just happens to be actuated (for a normally open reed switch, it becomes closed; for a normally closed reed switch, it becomes disconnected). At this time, when there is a whole piece of magnetic material, such as iron plate close to the magnet and the reed switch at the same time, the reed switch will once again be actuated, restored to the state when there is no magnetic field; when the iron plate leaves, the reed switch will be actuated in the opposite direction. The reed relay has a sturdy structure with sealed contacts and high durability, and can be used as a position limiting switch for mechanical equipment, or for detecting whether an iron door, window, etc. is in a specified position.
Optical relays are AC/DC semiconductor relays that integrate a light-emitting device with a light-receiving device. The input side and output side are electrically insulated, but signals can be transmitted by optical signals.
It is characterized by semi-permanent life, small current drive signal, high impedance insulation withstand voltage, ultra-compact, optical transmission, no contact and so on.
Mainly used in measurement equipment, communication equipment, security equipment, medical equipment and so on.
Time RelayTime Relay is a kind of control electric appliance that uses electromagnetic principle or mechanical principle to realize time-delay control. It has many types, air damping type, electric type and electronic type.
In the AC circuit is often used in the air-damped time relay, it is the use of air throttling through small holes in the principle to obtain the delay action. It consists of electromagnetic system, time-delay mechanism and contact three parts.
Time relays can be divided into two types: power-on time-delay type and power-off time-delay type.
The air-damped time relay has a large delay range (0.4-60s and 0.4-180s), and it has a simple structure but lower accuracy.
When the coil is energized (voltage specifications are ac380v, ac220v or dc220v, dc24v, etc.), the armature and the pallet are attracted by the iron core and move down instantaneously, making the instantaneous action contacts turn on or off. But the piston rod and lever can not follow the armature at the same time with the fall, because the upper end of the piston rod connected to the rubber membrane in the air chamber, when the piston rod in the release of the spring under the action of the beginning of the downward movement of the rubber membrane and then downward concave, the air above the air chamber air becomes thin and make the piston rod by the damping effect of a slow decline. After a certain period of time, the piston rod down to a certain position, it will be through the lever to promote the action of the delay contact, so that the movable break contact disconnect, movable close contact closure. From the coil is energized to the delay contact to complete the action, this time is the delay time of the relay. The length of the delay time can be changed by adjusting the size of the air inlet hole in the air chamber with a screw.
After the attractor coil is de-energized, the relay recovers by the action of the recovery spring. Air is quickly discharged through the air outlet hole.
Three, what is the role of different relays relay is an automatic switching element with isolation function, widely used in remote control, telemetry, communications, automatic control, electromechanical integration and power electronic equipment, is one of the most important control components.
Relays generally reflect certain input variables (such as current, voltage, power, impedance, frequency, temperature, pressure, speed, light, etc.) of the sensing mechanism (input part); there can be controlled circuits to realize the "through", "break" control The actuator (output part); in the relay between the input part and the output part, there is the input coupling isolation, functional processing and the output part of the drive of the intermediate institutions (drive part).
As a control element, in general, the relay has the following roles:
1) Expand the scope of control: for example, multi-contact relay control signal reaches a certain value, according to the different forms of contact groups, at the same time, switching, disconnecting, and connecting multiple circuits.
2) amplification: for example, sensitive relays, intermediate relays, etc., with a very small amount of control, you can control a very high power circuit.
3) synthesizing signals: for example, when multiple control signals are fed into a multi-winding relay in a specified form, they are compared and synthesized to achieve a predetermined control effect.
4) automatic, remote control, monitoring: for example, the relay on the automatic device together with other electrical appliances, can be formed into a program control line, so as to achieve automatic operation.
Four, relay classification (1) according to the working principle of the relay or structural features classification
1. Electromagnetic relay: the use of the input circuit within the circuit in the electromagnet core and the armature between the suction generated by the role of work of a kind of electrical relays.
2. Solid state relay: refers to the electronic components to fulfill its function without mechanical moving parts, input and output isolation of a relay.
3. temperature relay: when the external temperature reaches a given value and the action of the relay.
4. reed relay: the use of sealed in the tube, with a contact reed and armature magnetic circuit of the double role of the reed action to open, close or convert the line relay
5. time relay: when added or removed from the input signal, the output part of the time delay or time limit to the specified time before closing or disconnecting its controlled line relay.
6. high-frequency relay: used to switch high-frequency, radio frequency line with minimum loss relay.
7. Polarization relay: polarized magnetic field and control current through the control coil of the magnetic field generated by the combined action of the relay. The direction of action of the relay depends on the direction of the current flowing in the control coil.
8. Other types of relays: such as optical relays, acoustic relays, thermal relays, instrumentation relays, Hall effect relays, differential relays and so on.
(2) according to the external dimensions of the relay classification
1. miniature relay
2. ultra-miniature miniature relays
3. small miniature relays
Note: for the sealing or closed relay, the size of the external dimensions for the relay body of the three mutually perpendicular direction of the largest dimensions, excluding mounting parts, lead-in ends, compression bars, crimping, flanging and sealing soldering dimensions. flanges and sealing joints.
(3) according to the load classification of the relay
1. micro-power relay
2. weak power relay
3. medium-power relay
4. high-power relay
(4) according to the protection characteristics of the relay classification
1. sealed relay
2. closed relay
3. closed relay
3. closed relay
5. closed relay
6. closed relay
6. closed relay
7.
3. Open type relays
(5) According to the principle of action of the relay can be categorized
1. electromagnetic type
2. inductive type
3. rectifier type
4. electronic type
5. digital type and so on
(6) According to the reaction of the physical quantity can be classified
1. current relay
1. Voltage relays
3. Power direction relays
4. Impedance relays
5. Frequency relays
6. Gas relays
7. Measurement relay
3. Time relay
4. Intermediate relay
5. Signal relay
6. Exit relay