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Practical application and failure problems of contactors.

The contact contact of the contactor is not reliable, which will increase the contact resistance between the dynamic and static contacts, resulting in the temperature of the contact surface being too high, making the surface contact become point contact, and even non-conduction.

1. The reasons for this failure are:

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

2) Long-term use, oxidation of the contact surface.

3) Arc ablation causes defects, burrs or the formation of metal chips.

4) There is a jamming phenomenon in the moving part.

Second, the fault handling methods are:

1) For the oil, hair or foreign matter on the contact, you can use a cotton cloth dipped in alcohol or gasoline to scrub.

2) If it is a silver or silver-based alloy contact, when the oxide layer is formed on the contact surface or a slight burn and blackening are formed under the action of the arc, it generally does not affect the work, and can be scrubbed with alcohol and gasoline or carbon tetrachloride solution. Even if the surface of the contact is burned uneven, only use a fine file to remove the surrounding splash beads or burrs, and do not file too much, so as not to affect the life of the contact.

For copper contacts, if the degree of burn is mild, only need to use a fine file to repair and smooth the uneven places, but it is not allowed to polish with a fine abrasive cloth, so as not to leave quartz sand particles between the contacts and not maintain good contact; If the burn is severe and the contact surface is low, the contact must be replaced.

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

3. Contactor contact adhesion is a serious failure. Because the contact sticking can cause the machine to lose control, and even cause mechanical accidents and personal injury accidents. The reasons for this failure are:

1. The load is too heavy and the contact capacity is too small.

2. The operation frequency is too high.

3. The power supply voltage is too low, resulting in insufficient suction of the magnetic system and repeated vibration of the contact, resulting in arc welding.

4. The initial pressure of the contact is too small, and the beating is very strong when the inductive load is closed, and arc fusion welding occurs.

5. The spark is too large.

6. Improper installation.

Fourth, the noise of the AC contactor in operation is very large, and the following treatment can be made:

1. The power supply voltage is insufficient, and the suction power of the electromagnet is not enough to produce noise, so try to increase the voltage of the operation circuit.

2. If the magnetic system is not properly assembled or skewed by vibration or the parts are stuck, the core cannot be flattened, resulting in noise. The system should be adjusted during processing to identify and eliminate the causes of inflexible parts.

3. If the polar surface is rusty or there are foreign objects (such as oil scale, dust, flower hair, etc.) invading the polar surface of the iron core, the polar surface of the iron core should be cleaned at this time.

4. Due to the excessive pressure of the contact spring, the electromagnet noise is generated, and the contact spring pressure can usually be adjusted.

5. If the noise is generated due to the breakage of the short-circuit ring, the iron core or short-circuit ring should be replaced.

6. If the pole surface of the iron core is worn excessively and uneven, the iron core should be replaced.

7. The coil is short-circuited between turns, and the coil can usually be replaced.

The single-phase current is greater than 20A, and the three-phase current is greater than 10A

The role of AC contactors:

1. In electrical engineering, because it can quickly cut off the AC and DC main circuit and can frequently connect with the high-current control (up to 800A) circuit, it is often used in the motor as the control object, and can also be used to control the power load of factory equipment, electric heaters, working machines and various power units, etc., the contactor can not only turn on and cut off the circuit, but also has the role of low voltage release protection.

2. Turn on and off the circuit of the electrical appliance.

3. The contactor has a large control capacity, which is suitable for frequent operation and long-distance control, and is one of the important components in the automatic control system.

4. In industrial electrical, there are many types of contactors, and the working current ranges from 5A-1000A, and its use is quite extensive.

Reasons for the need for an AC contactor:

1. AC contactor is widely used as an interrupting and control circuit for electric power. It uses the main contact to open and close the circuit, and the auxiliary contact to execute the control command.

The main contact generally only has a normally open contact, while the auxiliary contact often has two pairs of normally open and normally closed contacts, and the small contactor is often used as an intermediate relay 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.

2. Because the contactor is an automatic switcher used to turn on or disconnect the AC and DC main circuit or large-capacity control circuit with load, the main control object is the motor, and it is also used for other power loads, such as electric heaters, welding machines, lighting equipment, contactors can not only connect and cut off the circuit, but also have the role of low voltage release protection.

3. The contactor has a large control capacity, which is suitable for frequent operation and long-distance control, and is one of the important components in the automatic control system.

One: Generally, the three-phase contactor has a total of 8 points, three inputs, three outputs, and two control points. The output and input are corresponding, and it is easy to see. If you want to add self-locking, you also need to connect the wire from one of the terminals at the output point to the control point.

The above is very correct, add some, specifically, there is an application example for reference (circuit diagram) connected to a 3-phase motor This is a typical circuit diagram of an AC contactor controlling a three-phase motor, in addition, a power button, a stop button.

Hope it works for you.

AC contactor 1L L 3 is the power side of the contactor, connected to the three-phase power supply.

2t t t3 is load side load. no is the normally open contact, and the contact is closed after the power is turned on, and the normally closed contact becomes normally closed. NC is a normally closed contact, which becomes normally open when energized.

The use of AC contactors is as follows:

AC contactor 1L L 3 is the power side of the contactor, connected to the three-phase power supply.

2t t t3 is load side load. no is the normally open contact, and the contact is closed after the power is turned on, and the normally closed contact becomes normally closed. NC is a normally closed contact, which becomes normally open when energized.

The three-phase power supply is connected to the three main contacts of the AC contactor, and the other three main contacts are connected to the motor, and the AC contactor coil is connected to the control circuit, and the suction of the AC contactor can be controlled by the button.

AC contactor: AC contactor is a kind of contactor, and its typical structure is divided into double break direct action type (LC1-D F*) and single break rotation type (LC1-B*). At present, the most commonly used products are mainly CJX2 series, CJ20 series, CJT1 series, 3TB, B series, etc.

AC contactor is a kind of electromagnetic AC contactor with normally open, three-pole main contact, and air as arc extinguishing medium.

Its components include: coil, short-circuit ring, static iron core, moving iron core, moving contact, static contact, auxiliary normally open contact, auxiliary normally closed contact, pressure spring sheet, reaction spring, buffer spring, arc extinguishing cover and other original components, AC contactor CJO, CJIO, CJ12 and so on.

AC contactor is the most widely used low-voltage control appliance in electric drive and automatic control systems. As an actuator, it is used to turn on and break lines, or frequently control the operation of equipment such as motors. It is composed of dynamic and static main contacts, arc extinguishing covers, dynamic and static iron cores, auxiliary contacts and bracket shells.

After the electromagnetic coil is energized, the moving iron core is engaged under the action of electromagnetic force, and the moving contact is in contact with the static contact directly or through the lever transmission, and the circuit is connected. After the solenoid coil is powered off, the moving iron core automatically returns under the action of the return spring, commonly known as release, the contacts are separated, and the circuit is broken.

The carrying current of the AC contactor is very large, generally the internal suction coil to control its action or not, and the control coil is operated by various types of relays connected in series with it, after thunder, it will trip because the relay of the AC contactor has an overcurrent or grounding protection function, when there is lightning on the line, it will control the action of the AC contactor, cut off the load power supply, to protect the equipment, so as not to be damaged by high voltage, high current or grounding safety hazards.

The function of the contactor is to use a small current circuit to control the large current load, which can be controlled from a distance, and can be self-locking and interlocking at the same time to prevent accidents caused by malfunction.

Contactors are divided into AC contactors (voltage AC) and DC contactors (voltage DC), which are used in electricity, power distribution and consumption. Contactor in a broad sense refers to the electrical appliances that use the current flowing through the coil to generate a magnetic field and close the contact to control the load in industrial electricity.

The function of the AC contactor is to turn on or off the power supply, and can replace the automatic switching function that manual switching is not capable of. It is widely used in automatic control, because most of them are used to control AC electrical appliances, so it is more convenient for the contactor itself to share AC power with electrical appliances as a power supply.

The AC contactor is equivalent to a gate knife, which will automatically trip when the electricity is abnormal (leakage or short circuit), and is generally used for 380V alternating current on the construction site.

Generally, large-scale equipment needs to be frequently started and removed, and the current is relatively large, so it is more dangerous and cumbersome for people to directly operate the switch; The contactor is a kind of relay that can be started and disconnected frequently, and the main circuit of high current can be controlled through the secondary coil circuit of the contactor. In this way, the relatively large and dangerous current circuit is controlled by controlling the small current circuit, which not only improves the safety performance but also avoids the cumbersome frequent opening and closing.

AC contactors are electronically controlled switches that can control motors from a distance.

The control loop should first connect the two buttons that control the forward and reverse rotation stop in series respectively, then connect the two buttons that control the forward and reverse start in parallel and connect with one end of the stop button, the other end of the stop button is ready to be connected with the power supply, and then the normally open auxiliary contacts of the forward and reverse main contactors are connected in parallel at both ends of the corresponding start buttons respectively, and then the normally closed auxiliary contacts of each autonomous contactor are connected in series to the start circuit of each other, that is to say, the normally closed series of the forward rotation is connected in series at one end of the reverse start button, The normally closed contact of the corresponding reversal should be connected in series with the start button of the forward rotation to play the role of interlocking, (that is, the normally closed auxiliary contact of the contactor will disconnect the reversing starting circuit during the forward rotation operation, and vice versa, this is still the case, in order to prevent pressing the next button at the same time from causing a short circuit between the phases of the primary circuit, which will be explained later). Then the other end of the two normally closed contacts is connected with the coil section of the main contactor of the corresponding starting loop respectively (that is, the loop that controls the forward rotation ground start is connected in series with the coil of the forward contactor, and the reverse start control loop is connected in series with one end of the reverse main contactor coil, don't be confused) connect the other ends of the two coils in parallel together and then access one end of the normally closed contact of the thermal relay, and the other end of the normally closed contact of the thermal relay is ready to be connected with the neutral point n or another phase wire, This depends on the voltage of the main contactor coil (220V is connected to the neutral point N, and 380V is connected to another phase wire), and it is also necessary to go through a control fuse at the front end of the control loop, that is, the stop button is ready to be connected to the power supply, and now it can only be said that the control loop is connected. The main circuit is connected below, and the main circuit needs 2 contactors, which are used to connect the main circuit when it is forward and reversed, so the upper end of the main contact of the two contactors is connected with the 3 phase wires of the three-phase AC power supply respectively, and the contact corresponding to the lower end of the main contact should be swapped with any two of the wires, and then connected to the 3 connecting pieces after the motor winding is connected in the order after the exchange (for example, the three-phase power supply ABC is connected to the upper port of a contactor in sequence, And here in the same order with another contactor upper port in parallel, then the lower port of one of the contactors is also connected to the motor winding connecting piece in the order of ABC, and at the same time the lead wire is connected to the lower port of another contactor in the order of ACB or BAC or CBA), in addition, the main contact of the thermal relay is connected in series between the contactor and the motor junction box wiring, and the fuse is also connected in series between the power lead and the upper port of the contactor. In this way, all the circuits are roughly connected.

What control do you want to use, self-locking or jogging.