Electromagnetic relay
Electromagnetic relay is generally composed of iron core, coil, armature, contact reed and so on.
Electromagnetic relay working principle
As long as the coil ends with 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, which drives the armature of the movable 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
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 the 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 Relay
Thermal 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, a constant magnetic ring, a reed switch, a thermally conductive mounting piece, a 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 Relay
Reed Relay is a relay that uses a coil to generate a magnetic field to actuate a reed switch,
as a coil sensing device. 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 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.
Photorelays
Photorelays 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...etc..
Mainly used in measurement equipment, communication equipment, security equipment, medical equipment...etc..
Time Relay
Time Relay is a kind of control appliance that utilizes electromagnetic principle or mechanical principle to realize time delay control.
Relay
It has many types, such as air-damped 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 time-delay range (0.4-60s and 0.4-180s), and it has a simple structure, but the accuracy is lower.
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 instantly move down, so that the instantaneous action contacts are connected or disconnected. 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 rapidly discharged through the air outlet hole.
Intermediate relay
Features of intermediate relay:
Relay is made of multiple high-quality sealed small relays with low coil voltage, moisture-proof, dust-proof, without disconnecting wires, with high reliability, which overcomes the shortcomings of the electric
Intermediate Relay Sample Diagram
Magnetic intermediate relay with thin wires that can be easily disconnected; low power consumption, low temperature rise, no external high-power resistors, no need to be attached to a high power resistor, no need to be attached to a high-power resistor, no need to be attached to a high power resistor, no need to be attached to a high-power resistor. No external high-power resistors, can be installed and wired conveniently; relay contact capacity, long working life; relay action after the light-emitting tube instructions, easy to observe; delay only with the panel of the dial switch set, high delay accuracy, delay range can be set at 0.02-5.00S arbitrary.
Use of intermediate relay:
Intermediate relay is used in all kinds of protection and automatic control lines to increase the number of contacts and contact capacity of the protection and control circuit.
Classification of intermediate relay:
Low current start intermediate relay
Static intermediate relay
Time-delay intermediate relay
Electromagnetic intermediate relay
Elevator intermediate relay
Guideway intermediate relay
Principle of intermediate relay
Coil Energized, the moving iron core under the action of electromagnetic force suction, driving the action of the moving contacts, so that the normally closed contacts separate, normally open contacts closed; coil de-energized, the moving iron core under the action of the spring to drive the moving contacts reset, the working principle of the relay is when a certain input (such as voltage, current, temperature, speed, pressure, etc.) reaches a predetermined value, to make it act, in order to change the working state of the control circuit, so as to achieve the established control or protection purposes. In this process, the relay mainly plays the role of transmitting signals .
The role of the intermediate relay
General circuit is often divided into two parts of the main circuit and the control circuit, the relay is mainly used for the control circuit, the contactor is mainly used for the main circuit; through the relay can be realized with a control signal to control the other way or several signals, to complete the control of the start, stop, linkage, etc., the main control object is the contactor; contactor contactor is relatively large, strong load-bearing capacity, through it to the control circuit, the relay can be used to control the other way or several signals. Strong load-bearing capacity, through which to realize the control of weak power to strong power, the control object is electrical appliances.
1. Instead of small contactors
The contacts of intermediate relays have a certain load capacity, when the load capacity is relatively small, it can be used to replace the small contactors, such as electric roller shutters and the control of some small appliances. The advantage of this is not only can play the purpose of control, but also can save space, so that the control part of the electrical appliances made more delicate.
2. Increase the number of contacts
This is the most common use of intermediate relays, for example, in the circuit control system, a contactor contact needs to control more than one contactor or other components when it is in the line to increase the number of intermediate relays.
3. Increase contact capacity
We know that the contact capacity of the intermediate relay is not very large, but also has a certain load carrying capacity, while the current required for its drive is very small, so you can use the intermediate relay to expand the contact capacity. For example, generally can not directly use the output of the inductive switch, transistor to control the load of the larger electrical components. Instead, the use of intermediate relays in the control line, through the intermediate relay to control other loads, to achieve the purpose of expanding the control capacity.
4. Conversion contact type
In the industrial control line, there is often such a situation, the control requirements need to use the contactor normally closed contact to achieve the purpose of control, but the contactor itself with the normally closed contact has been used up, can not complete the control task. At this time, an intermediate relay can be connected in parallel with the original contactor coil, with the intermediate relay normally closed contacts to control the corresponding components, to convert the contact type, to achieve the desired control purpose.
5. Used as a switch
In some control lines, some electrical components are often used in the intermediate relay, with its contacts open and closed to control, such as color TV or monitor in the common automatic degaussing circuit, transistor control of the intermediate relay, so as to achieve the control of the degaussing coil on and off the role.
6. Conversion voltage
7. Elimination of interference in the circuit
Power direction relay
When the input quantity (such as voltage, current, temperature, etc.) reaches the specified value, so that the output circuit to be controlled by the conductor or disconnect the electrical appliances. Can be divided into electrical quantity (such as current, voltage, frequency, power, etc.) relay and non-electrical quantity (such as temperature, pressure, speed, etc.) relay two categories. It has 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.
Test Methods
1, the coil resistance: available universal meter R × 10 Ω file to measure the resistance of the relay coil, so as to determine whether the coil exists in the open-circuit phenomenon. The resistance value of the relay coil and its working voltage and working current have a very close relationship, through the coil resistance value can be calculated by its use of voltage and working current.
2, measurement of contact resistance: with the multimeter resistance gear, measuring the normally closed contacts and moving point resistance, the resistance value should be 0; and normally open contacts and moving point resistance value is infinity. This can distinguish that is normally closed contacts, that is normally open contacts.
3, measuring the suction voltage and suction current: find an adjustable regulated power supply and ammeter, to the relay input voltage, and in the power supply circuit into the ammeter for monitoring. Slowly increase the supply voltage, hear the relay suction sound, write down the suction voltage and suction current. For the sake of accuracy, you can try several times and seek the average value. Measurement of release voltage and release current: also like the above connection test, when the relay is absorbed, and then gradually reduce the supply voltage, when you hear the relay release sound again, write down the voltage and current, you can also try more than a few times and get the average release voltage and release current. In general, the release voltage of the relay is about 10-50% of the suction voltage, if the release voltage is too small (less than 1/10 of the suction voltage), it can not be used normally, which will cause a threat to the stability of the circuit so that the work is not reliable.
Common types
1, overcurrent relay
Overcurrent relay, referred to as CO, is from the current exceeds its set value and the action of the relay, can be done to protect the system line and overload, the most commonly used is the induction overcurrent relay, is the use of electromagnets and aluminum or copper rotating disk relative to the principle of electromagnetic induction to make the rotating disk rotation to achieve the protection effect. protection.
Principle of action:
Induction overcurrent relay is the use of current transformer secondary side current, in the relay to generate a magnetic field, in order to promote the rotation of the disk, but the flow of current must be greater than the current value of the current scalar plate in order to rotate.
2, over-voltage relay
Over-voltage relay, referred to as OV, its main purpose is to when the system's abnormal voltage rises to 120% of the rated value or more, over-voltage relay action to make the circuit breaker jumped off to protect the power equipment from damage, the inductive over-voltage relay structure and action principle and over-current relay is similar to the main coil is different.
3, undervoltage relay
Undervoltage relay, referred to as UV, its structure and overvoltage relay is the same, the difference is that the internal contacts and when the applied voltage turntable will immediately turn.
4, grounding overvoltage relay
Grounding overvoltage relay, referred to as OVG, or grounding alarm relay referred to as GR, its structure is the same as the overvoltage relay, used in three-phase, three-wire, non-grounded system, connected to the open triangle grounding ground transformer, used to detect the zero-phase voltage.
5, grounding overcurrent relay
Grounding overcurrent relay, referred to as GCR, is a high-voltage line grounding protection relay.
Main uses:
1) grounding overcurrent protection of high-resistance grounding system;
2) grounding protection of generator stator winding;
3) interlayer short circuit protection of split-phase generator;
4) overheating protection of grounded transformer.
6, selective grounding relay
Selective grounding relay, referred to as SG, also known as directional grounding relay, referred to as DG, used in the ungrounded system for the protection of distribution lines, overhead lines and cable systems can also be used.
Selective grounding relay: the grounding voltage transformer detects the zero-phase sequence current in case of line grounding, selective grounding relay can indeed indicate the fault line and alarm, and according to its needs to select the fault line will be disconnected, and continue to send power to the normal line.
7, the lack of phase relay
Lack of phase relay, referred to as OPR, or lack of phase protection relay, referred to as PHR, in the three-phase line, when the power supply end of a line breaks down and cause a single-phase, if the line is not immediately cut off, the motor will make the single-phase operation and burned.
8, ratio differential relay
Ratio differential relay, referred to as RDR, is used to do the transformer AC motor, AC generator differential protection, used in the past overcurrent protection relay, is an external fault generated by the abnormal current flow through the protection equipment, if the transformer, the first and second side of the current imbalance or inconsistency of the characteristics of the current transformer, in these cases, the phenomenon will expand. In these cases, this phenomenon will be extended several times, and make the relay inaccurate operation.
Selection conditions
1, the first to understand the necessary conditions
1) the control circuit supply voltage, the maximum current can provide;
2) the voltage and current in the controlled circuit;
3) the controlled circuit needs a few groups, what form of contacts. Selection of relays, the general control circuit supply voltage can be used as the basis for selection. The control circuit should be able to provide sufficient operating current to the relay, otherwise the relay absorption is unstable.
2, consult the relevant information to determine the conditions of use, you can look for relevant information to find out the need for the relay model and specification number. If you have a relay on hand, you can check whether you can utilize it based on the information. Finally, consider whether the size is appropriate.
3, pay attention to the volume of appliances. If it is used for general appliances, in addition to considering the chassis volume, small relays mainly consider the circuit board installation layout. For small appliances, such as toys, remote control devices should be selected ultra-small relay products.
Type sign
Generally, the type of domestic relay naming consists of four parts: the first part + the second part + the third part + the fourth part.
The first part of the relay model number uses letters to indicate the main name of the relay type.
JR - small power relay
JZ - medium power relay
JQ - high power relay
JC - magneto-electric relay
JU - thermal relay or temperature relay
JT - special relay
JM - pulse relay
JS - time relay
JAG - reed relay
The second part of the relay model number is indicated by the letters to indicate the shape of the relay
Circuit diagram (13 sheets)
Shape characteristics.
W--Micro
X--Small
C--Cubic
The third part of the relay model number uses a number to indicate the Product serial number.
The serial number is indicated by a number
The fourth part of the relay model number is indicated by a letter indicating the protection characteristics.
F - Enclosed
M - Sealed
Example: JRX-13F (Enclosed small power mini relay).
JR - small power relay
X - small
13 - serial number
Selection method