Connection:
One: Generally, a three-phase contactor has eight points, three inputs, three outputs and two control points. Output and input correspond, so it is easy to see. If you want to add self-locking, you need to connect the wire from one terminal of the output point to the control point.
Two: First of all, we should know the principle of AC contactor. He added an external power supply to the coil to generate an electromagnetic field. When the power is on, the contacts are disconnected after the power is off. After knowing the principle, you should find out the contacts of the external power supply, that is, the two contacts of the coil, which are generally at the lower part and both sides of the contactor. Other inputs and outputs are generally in the upper part, which is clear at a glance. Also pay attention to the voltage of the external power supply (220V or 380V), which is generally marked. And pay attention to whether the contact is normally closed or normally open. If there is self-locking control, just arrange the circuit according to the principle.
Selection, Operation and Maintenance of AC Contactor
(1) Select:
(1) The rated current of the main circuit contact should be greater than or equal to the rated current of the controlled equipment, and the starting current of the motor should also be considered when controlling the contactor of the motor. In order to prevent the main contact of frequent contactor from ablation, the rated current of frequent contactor can be reduced.
(2) The rated voltages of the contactor electromagnetic coil are 36V, 1 10V, 220V, 380V, etc. The electromagnetic coil is allowed to be used in the range of 80% ~ 105% of the rated voltage.
(2) Operation and maintenance: ① Check whether the passed load current is within the contactor rating during operation: 1;
2) Whether the opening and closing signals of the contactor are consistent with the circuit state;
3) Whether the running sound is normal and whether there is any discharge sound with poor contact;
4) Whether the electromagnetic coil is overheated and whether the electromagnet short-circuit ring is abnormal.
5) Whether the arc extinguishing cover is loose or damaged;
6) auxiliary contact with and without burning;
7) Whether the transmission part is damaged;
8) Whether there are unfavorable factors such as excessive vibration, poor ventilation and excessive dust in the surrounding working environment.
② Maintenance:
When maintaining electrical equipment, contactors should be maintained together.
1) External maintenance:
A. clean external dust;
B. Check whether the fastener is loose, especially the conductor connection part, to prevent the contact from loosening and heating;
2) Contact system maintenance:
A. Check whether the positions of dynamic and static contacts are aligned and whether the three phases are closed at the same time. If there is any problem, adjust the contact spring;
B. Check the degree of contact wear, the wear depth shall not exceed 1mm, and replace the contact in time if it is burnt or falls off after welding; When slightly burned, it generally does not affect the use. Sandpaper is not allowed to be used when cleaning contacts, and plastic files should be used;
C. Measure the insulation resistance between phases, and the resistance value shall be not less than10mΩ; ;
D. Check whether the auxiliary contact moves flexibly, and the contact stroke should meet the specified value. Check whether the contacts are loose and fall off. If problems are found, repair or replace them in time.
3) iron core part maintenance:
A. Remove dust, especially the dust between the moving parts and the contact surface of the iron core;
B. check the fastening of the iron core. Loose iron core will increase running noise;
C. If the iron core short-circuit ring falls off or breaks, it should be repaired in time.
4) electromagnetic coil maintenance:
A. measure the insulation resistance of the coil;
B. Whether the coil insulation is discolored or aged, and the surface temperature of the coil should not exceed 65℃; ;
C. Check the connection of coil leads, and repair them in time if there is welding or burning. 5) local maintenance of arc extinguishing cover:
A. check whether the arc extinguishing cover is damaged;
B. Whether the position of the arc extinguishing cover is loose or not, and whether the position changes;
C, removing metal particles and sundries in the gap of the arc extinguishing cover.
5 working principle of vacuum AC contactor
Vacuum contactor uses vacuum as arc extinguishing medium, and the main contact is sealed in a special vacuum arc extinguishing tube. When the operating coil is energized, the armature is attracted, and the contact is closed under the action of the contact spring and the self-closing force of the vacuum tube; When the working coil is powered off, the reaction spring overcomes the self-closing force of the vacuum tube, releases the armature and disconnects the contact. When the contactor breaks the current, platinum scale formed by metal vapor will be formed in the contact gap, which will affect the service life of the contactor.