1, the use of classification
The contactor is an automated control appliance. The contactor is mainly used for frequent interruption or breaking of AC and DC circuits, with large control capacity, long distance operation, with the relay can be achieved timing operation, interlock control, a variety of quantitative control and pressure and undervoltage protection, In the automatic control circuit, the main control object is the motor, can also be used to control other electric load, such as electric heater, lighting, welding machine, capacitor group and so on.
Contactor according to the type of charged current can be divided into AC contactor and DC contactor. Here mainly describes the commonly used AC contactor. AC contactor can be divided into two kinds of electromagnetic and vacuum.
2, model description
(1) The above model is the standard model, in recent years, the newly developed B series AC contactor, the model is BXX.
(2) electromagnetic AC contactor model for the CJ. Vacuum AC contactor model for the CZ.
3, electromagnetic AC contactor structure and working principle
(1) structure:
The contactor is mainly composed of electromagnetic system, contact system, arc extinguishing system and other parts.
① electromagnetic system: electromagnetic system, including electromagnetic coil and core, is an important part of the contactor, relying on it to drive the contact closure and disconnect.
② contact system: contact is the implementation of contactor, including the main contact and auxiliary contacts. The main contact function is to connect and break the main circuit, control the larger current, and auxiliary contact is in the control loop to meet the requirements of various control methods.
③ arc extinguishing system: arc extinguishing device used to ensure that the contact disconnect the circuit, the arc generated by the reliable off to reduce the damage to the contact of the arc. In order to quickly extinguish the arc when the break, usually contactor are equipped with arc extinguishing device, the general use of semi-sealed vertical seam clay muffler, and with a strong magnetic circuit.
④ other parts: a shell, spring, short circuit, transmission and so on.
(2) working principle:
When the contactor solenoid is not energized, the reaction force of the spring and the weight of the armature keep the main contact in the open position. When the electromagnetic coil through the control circuit connected to the control voltage (usually rated voltage), the electromagnetic force to overcome the reaction force of the spring to the armature suction to the static core, driving the main contact closed, connected to the circuit, auxiliary contact with the action.
4 AC contactor selection and operation and maintenance
(1) Selection:
① The rated current of the main circuit contact should be greater than or equal to the rated current of the controlled device. The contactor of the control motor should also consider the starting current of the motor. In order to prevent frequent operation of the contactor main contact ablation, frequent action of the contactor rated current can be reduced.
② The rated voltage of the solenoid of the contactor is 36V, 110V, 220V, 380V and so on. The electromagnetic coil is allowed to be used within the range of 80% ~ 105% of the rated voltage.
(2) operation and maintenance: ① running check items: 1) through the load current is within the contactor rating;
2) The splitter signal of the contactor indicates whether it is in line with the circuit status;
3) whether the normal operation of the sound, whether due to poor contact with the discharge sound;
4) Whether the electromagnetic coil overheating, electromagnet short-circuit whether the abnormal.
5) whether the release of arcing and damage;
6) auxiliary contact with or without burning situation;
7) whether the transmission part of the damage;
8) around the operating environment with or without adverse factors, such as vibration is too large, poor ventilation, dust and so on.
② maintenance:
In the electrical equipment maintenance work, should be carried out on the contactor maintenance work.
1) External maintenance:
A. Cleaning external dust;
B. Check whether the fasteners are loose, especially the conductor connection part, to prevent the contact loose and heat;
2) Contact system maintenance:
A. Check the dynamic and static contact position is correct, three-phase is closed at the same time, if the problem should be adjusted contact spring;
B. Check the degree of contact wear, wear depth of not more than 1mm, the contact has burned, open welding off, the time to be replaced; slightly burned, generally does not affect the use. Clean the contacts do not allow the use of sandpaper, should use plastic filing;
C. Measuring interphase insulation resistance, the resistance of not less than 10MΩ;
D. Check the auxiliary contact action is flexible, contact travel should meet the specified value, check the contact with or without loose off, find the problem, should be promptly repaired or replaced.
3) core part of the maintenance:
A. Cleaning dust, especially moving parts and iron suction contact between the surface;
B. Check the core of the tightening situation, loose core will cause the operation to increase the noise;
C. Core short circuit ring off or broken to be timely repair.
4) Electromagnetic coil maintenance:
A. Measuring coil insulation resistance;
B. Coil insulation with or without color, aging phenomenon, the coil surface temperature should not exceed 65 ° C;
C. Check the coil lead connection, if open welding, burning should be timely repair. 5) Part of the arc cover maintenance:
A. Check the arc cover is damaged;
B. Is the release hood position loose and position change?
C. Clear the metal particles and debris in the gap of the arc cover.
5 vacuum AC contactor works
Vacuum contactor to vacuum as the arc medium, the main contact sealed in a special vacuum arc tube. When the coil is energized when the coil is energized, the contact is closed under the action of the contact spring and the vacuum tube self-closing force. When the operation coil is de-energized, the reaction spring releases the armature to overcome the self-closing force of the vacuum tube. When the contactor breaks current, a vacuum arc consisting of metal vapor and other charged particles is formed in the contact gap. Because the vacuum medium has a high dielectric strength, and the media recovery speed is very fast, the vacuum arc time is generally less than 10ms.
Vacuum contactors and vacuum circuit breakers have common characteristics:
(1) breaking capacity: breaking current up to 10 to 20 times the rated current;
(2) long life: electrical life of several hundred thousand times, the mechanical life of up to one million times;
(3) small size, light weight, no arcing distance, safe and reliable;
(4) easy maintenance, the main contact without maintenance, running noise is small, the operation is not affected by harsh environments;
(5) can be operated frequently.
6 Vacuum contactor application and maintenance
(1) Vacuum contactor for AC 50Hz, the main circuit rated working voltage 1140V, 660V, 380V power distribution system. For the frequent operation of the larger load current, in the industrial enterprises are widely selected, especially for harsh environment and flammable and explosive dangerous places.
(2) Vacuum contactor inspection and maintenance:
① vacuum contactor vacuum tube interrupter maintenance work and vacuum circuit breaker is basically the same, can be combined with the controlled equipment at the same time maintenance.
② Vacuum contactor should be checked regularly:
1) Check the opening and the distance of the vacuum tube every six months.
2) check its performance every year;
3) quarterly should be checked once the auxiliary contact with or without damage;
4) every 1 to 2 years with the pressure test method to detect the vacuum arc tube vacuum.
③ maintenance:
Vacuum contactor maintenance work In addition to the vacuum arc tube, the other items are the same with the electromagnetic contactor.