The difference and connection between contactor and relay

1. The working principle of Contactor

A contactor is an electrical appliance that uses current to flow through a coil to generate a magnetic field in industrial electricity to close the contacts to control the load. The contactor is composed of electromagnetic system (iron core, static iron core, electromagnetic coil) contact system (normally open contact and normally closed contact) and arc extinguishing device. The principle is that when the electromagnetic coil of the contactor is energized, it will generate a strong magnetic field, which makes the static iron core produce electromagnetic attraction to attract the armature and drive the contact action: the normally closed contact is disconnected; the normally open contact is closed, the two are Linkage. When the coil is de-energized, the electromagnetic attraction disappears, and the armature is released under the action of the release spring to restore the contacts: the normally closed contact is closed; the normally open contact is disconnected.

In industrial electrical, there are many types of contactors, the current ranges from 5A to 1000A, and their uses are quite extensive.

In electrical engineering, a contactor is an automatic switcher used to connect or disconnect a load-carrying AC/DC main circuit or a large-capacity control circuit. The main control object is a motor. In addition, it is also used for other electrical loads, such as electric heating. Adapters, welding machines, lighting equipment, and contactors can not only connect and cut off the circuit, but also have a low-voltage release protection function. The contactor has a large control capacity. Suitable for frequent operation and remote control. It is one of the important components in the automatic control system.

2. Classification of Contactor

General contactors can be roughly divided into the following two categories:

1. AC contactor. There are mainly electromagnetic mechanisms. Contact system. Arc extinguishing device and other components. Commonly used is CJ10. CJ12. CJ12B and other series.

2. The DC contactor is generally used to control DC electrical equipment. The coil is supplied with DC power. The operation principle and structure of the DC contactor are basically the same as that of the AC contactor.

Because it can quickly cut off the AC and DC main circuits and can frequently connect to large current control (some types up to 800 amperes) circuit devices, it is often used in motors as control objects, and can also be used to control plant equipment ﹑Electric loads such as electric heaters, working mother machines and various electric power units, and used as remote control devices.

3. Function description of Contactor

The AC contactor uses the main contact to open and close the circuit, and the auxiliary contact to conduct the control loop. The main contact is generally a normally open contact, and the auxiliary contact often has two pairs of normally open contacts and a normally closed contact. Small contactors are often used as intermediate relays to cooperate with the main circuit. The contacts of the AC contactor are made of silver-tungsten alloy, which has good electrical conductivity and high temperature ablation resistance.

The power of the AC contactor's action comes from the magnetic field generated by the AC passing through a coil with an iron core. The electromagnet core is composed of two "hill" shaped young silicon steel sheets. One of the fixed iron cores is covered with a coil. The working voltage can be varied. choose. In order to stabilize the magnetic force, a short-circuit ring is added to the suction surface of the iron core. After the AC contactor loses power, it relies on the spring to reset. The other is the movable iron core, the structure is the same as the fixed iron core, used to drive the main contact and auxiliary contact to close and open.

The contactor above 20 amperes is equipped with an arc extinguishing cover, which uses the electromagnetic force generated when the circuit is disconnected to quickly break the arc to protect the contact.

The contact equipment can be operated at a high frequency. When used as a power switch on and off control, the maximum operating frequency can reach 1,200 times per hour.

The service life of the contactor is very high. The mechanical life is usually from millions to 10 million times, and the electrical life is generally from hundreds of thousands to millions of times.

4. Reasons for the unreliable contact of the contacts of the Contactor and the treatment methods

Insufficient contact of the contacts will increase the contact resistance between the moving and static contacts, causing the temperature of the contact surface to be too high, causing the surface contact to become a point contact, or even non-conduction. The reasons for this failure are:

(1) There are oil stains, flower hairs, and foreign objects on the contacts.

(2) Long-term use, the surface of the contact is oxidized.

(3) Defects, burrs or metal swarf particles caused by arc ablation.

(4) There is jamming in the moving part.

The treatment methods are:

(1) For oil stains, flower hairs or foreign objects on the contacts, you can wipe them with a cotton cloth dipped in alcohol or gasoline.

(2) If it is a silver or silver-based alloy contact, when an oxide layer is formed on the contact surface or a slight burn or blackening is formed under the action of an electric arc, it generally does not affect the work. It can be scrubbed with alcohol and gasoline or carbon tetrachloride solution. Even if the surface of the contact is burnt to be uneven, you can only use a fine file to remove the surrounding splashes or burrs. Do not file too much, so as not to affect the life of the contact. For copper contacts, if the burn is mild, just use a fine file to repair the unevenness, but it is not allowed to polish with a fine emery cloth, so as to prevent quartz sand particles from staying between the contacts and fail to maintain good contact; If the burn is severe and the contact surface is low, the contact must be replaced with a new one.

(3) The moving part is jammed and can be disassembled for maintenance.

5. Description of contactor structure

The AC contactor uses the main contact to open and close the circuit, and the auxiliary contact to conduct the control loop.

The main contact is generally a normally open contact, and the auxiliary contact often has two pairs of normally open contacts and a normally closed contact. Small contactors are often used as intermediate relays to cooperate with the main circuit.

The power of the AC contactor's action comes from the magnetic field generated by the AC passing through a coil with an iron core. The electromagnet core is composed of two "hill" shaped young silicon steel sheets. One of the fixed iron cores is covered with a coil. The working voltage can be varied. choose. In order to stabilize the magnetic force, a short-circuit ring is added to the suction surface of the iron core. After the AC contactor loses power, it relies on the spring to reset.

Simple contactor control

Simple contactor control

Relay

1. The working principle and characteristics of relay

When the input (such as voltage, current, temperature, etc.) reaches the specified value, the electrical appliance that makes the controlled output circuit turn on or off. It can be divided into electrical quantity (such as current, voltage, frequency, power, etc.) relays and non-electric quantity (such as temperature, pressure, speed, etc.) relays. It has the advantages of fast action, stable work, long service life and small size. It is widely used in power protection, automation, sports, remote control, measurement and communication devices.

A relay is an electronic control device, which has a control system (also called an input loop) and a controlled system (also called an output loop). It is usually used in automatic control circuits. In fact, it uses a smaller current to control a larger An "automatic switch" of electric current. Therefore, it plays the role of automatic adjustment, safety protection, and conversion circuit in the circuit.

2. Working principle and characteristics of electromagnetic relay

Electromagnetic relays are generally composed of iron cores, coils, armatures, contact reeds, etc. As long as a certain voltage is applied to both ends of the coil, a certain current will flow in the coil, which will produce electromagnetic effects. Under the action of electromagnetic force, the armature will overcome the pull force of the return spring and attract to the core, thereby driving the armature. The moving contact and the static contact (normally open contact) are pulled together. When the coil is de-energized, the electromagnetic attraction will disappear, and the armature will return to its original position under the reaction force of the spring, releasing the moving contact and the original static contact (normally closed contact). This pulls in and releases, so as to achieve the purpose of conducting and cutting off in the circuit. The "normally open and normally closed" contacts of the relay can be distinguished as follows: the static contact that is in the off state when the relay coil is not energized is called "normally open contact"; the static contact that is in the on state is called It is a "normally closed contact".

3. The working principle and characteristics of the thermal reed relay

The thermal reed relay is a new type of thermal switch that uses thermal magnetic materials to detect and control temperature. It is composed of a temperature-sensitive magnetic ring, a constant magnetic ring, a dry reed tube, a thermally conductive mounting sheet, a plastic substrate and some other accessories. The thermal reed relay does not use coil excitation, but the magnetic force generated by the constant magnetic ring drives the switching action. Whether the constant magnetic ring can provide magnetic force to the reed tube is determined by the temperature control characteristics of the temperature-sensitive magnetic ring.

4. Working principle and characteristics of solid state relay (SSR)

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

5. Relay function

a. Isolation function. Between the input part and the output part of the relay, there is an intermediate mechanism (drive part) for coupling and isolating the input, function processing and driving the output part.

b. Expand the scope of control. When the control signal of the multi-contact relay reaches a certain value, it can switch, break, and connect multiple circuits at the same time according to different forms of contact groups.

c. Zoom in. Sensitive relays, intermediate relays, etc., with a very small control quantity, can control a circuit with a large power.

d. Integrated signal. When multiple control signals are input to the multi-winding relay in a prescribed form, they will be compared and integrated to achieve the predetermined control effect.

e. Automatic, remote control and monitoring. The relay on the automatic device and other electrical appliances can form a program control circuit to realize automatic operation

6. Relay test

a. Measure the contact resistance. Use the resistance file of the universal meter to measure the resistance of the normally closed contact and the moving point. The resistance value should be 0, while the resistance value of the normally open contact and the moving point is infinite. From this, it can be distinguished which is a normally closed contact and which is a normally open contact.

b. Measure the coil resistance. The resistance value of the relay coil can be measured with the resistance profile of a universal meter to determine whether there is an open circuit phenomenon in the coil.

c. Measure the pull-in voltage and pull-in current. Find an adjustable regulated power supply and an ammeter, input a set of voltage to the relay, and connect an ammeter in the power supply loop for monitoring. Slowly increase the power supply voltage, and when you hear the sound of the relay closing, write down the closing voltage and the closing current. For accuracy, you can try several times and find the average value.

d. Measure the release voltage and release current. After the relay is pulled in, gradually reduce the power supply voltage. When you hear the relay releasing sound again, write down the voltage and current at this time. Under normal circumstances, the release voltage of the relay is about 10-50% of the pull-in voltage. If the release voltage is too small (less than 1/10 of the pull-in pressure), it cannot be used normally, which will threaten the stability of the circuit and make the work unreliable.

The difference between contactor and relay

Relay: used to control the circuit, the current is small, there is no arc extinguishing device, and 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 It cannot pass large currents and is generally not used for power circuits.

Contactor: Similar to a circuit breaker, it is used in the main circuit, has a large current, and has an arc extinguishing device. Generally, it can only operate under voltage. In fact, the principle is the same, mainly the contact capacity is different, the relay contact capacity is small, the contact can only pass a small current, mainly used for control, the contactor has a large capacity, the contact can pass a large current, and it is used for the main circuit more .

The principle of the contactor is the same as the voltage relay, but the load power controlled by the contactor is larger, so the volume is also larger. AC contactors are widely used as power breaking and control circuits. Relay is a small signal control electrical appliance, which is used for motor protection or automatic control of various production machinery.

Reasons and solutions for the unreliable contact of relays and contactors

Insufficient contact of the contacts will increase the contact resistance between the moving and static contacts, causing the temperature of the contact surface to be too high, causing the surface contact to become a point contact, or even non-conduction. The reasons for this failure are:

(1) There are oil stains, flower hairs, and foreign objects on the contacts.

(2) Long-term use, the surface of the contact is oxidized.

(3) Defects, burrs or metal swarf particles caused by arc ablation.

(4) The movement part has jamming phenomenon

1 commentaire

online Casino

online Casino

Hi there! This is kin of off topic but I need some
advice from ann established blog. Is it hard to set up
your own blog? I’m not very techincal but I can figure things out pretty fast.

I’m thinking about setting up my own but I’m not sur where to
start. Do you have anyy points or suggestions? Appreciate it https://vavadacasino.mystrikingly.com/

Laisser un commentaire