Failure analysis and maintenance of AC contactors

As AC contactors can be switched on and off frequently in the course of their work, it is inevitable that there will be wear and tear on the contactors in the course of their use. At the same time, sometimes improper use, or use in relatively harsh environments, will also shorten the life of the contactor or prone to failure, therefore, in the use of the time, but also according to the actual situation to choose, and in the use of timely maintenance, to avoid failure to bring greater trouble. In general, AC contactor common faults are the following, the following are for different fault analysis and maintenance.
1.contact failure and maintenance
Contacts include main contacts and auxiliary contacts, there is an essential difference between the two, the main contact is mainly used to connect the main circuit, connected to the control equipment, such as motors, welding machines, compressors and other high-power electrical equipment. Therefore, the main contact is required to have a strong over-current capability, which is generally greater than the rated current of the object to be controlled. The auxiliary contacts are mainly used for

The main contact is mainly used to switch on the control circuit and the current is smaller, generally between 1 and 5A. At the same time, there are obvious differences in the materials used between the two, therefore, when using them, they cannot be used interchangeably. The following analysis of contact failure and proposed solutions.
(1) contact fusion welding: moving, static contact surface melting after welding together can not break the phenomenon, called contact fusion welding. This situation generally occurs in the operation of high frequency or overload use, load end short circuit, contact spring pressure is too small, mechanical jamming, etc.. When these situations occur, you can replace the contactor or reduce the load, remove the short-circuit fault and replace the contact, adjust the contact surface pressure, and remove the blocking material.
(2) contact overheating or burns: refers to the work of the contact heat exceeds the rated temperature caused by contact overheating or burns. This situation is generally caused by the following circumstances: spring pressure is too small, the contact has oil, the ambient temperature is too high, the contact is used for long-term working system, the working current is too large causing the contact to break capacity is not enough. We can adjust the contact spring pressure, clean the surface of the contact, contactor lower capacity use, exchange the contactor with a larger capacity.
2.Coil failure and maintenance
The coil in the contactor to play a magnetic armature, and suction armature drive dynamic contacts and static contacts closed role,
Therefore, the coil suction force is strong, whether the contactor is connected to play an important role in reliable. The following for the coil fault analysis.
Analysis.
(1 ) coil overheating burned: coil overheating burned - the general situation is because the coil turns between short circuit, or the use of parameters and the actual
On the inconsistency, such as the rated voltage and the actual working voltage does not match. There is also a possibility that the core mechanical: card resistance, this situation, as long as the card blocking material can be excluded.

(2) Not sucked after power: In general, you can first check whether the coil is disconnected. In the case of power failure, you can use the multimeter
meter to measure whether the coil has resistance value. Whether the resistance value is within the specified range.
3.Other cases
(1) Insufficient suction: When the power supply voltage is too low or fluctuates too much, or the rated voltage of the coil itself is greater than the actual control circuit voltage, it will also make the suction of the contactor insufficient. This time can also be adjusted by adjusting the voltage, so that it and the actual rated voltage of the contactor can be in line. At the same time, if the movable part of the contactor is blocked, resulting in a tilted core, it can also lead to insufficient suction, we can remove the blocked object and adjust the core position. In addition, the reaction force spring is too large, can also lead to insufficient suction, just need to adjust the reaction force spring can be.
(2) contact can not be reset: first of all, you can observe whether the static and dynamic contacts are fused together, if this happens, generally
If this happens, the contacts can be restored by replacing them. At the same time we can also observe whether there is something stuck in the movable part, just need to take out the stuck object can be.
(3) Armature noise or vibration occurs in this case generally for the following:
① short circuit ring damage, can be removed by replacing the short circuit ring
②The power supply voltage is low. Can be increased by raising the power supply voltage
③The movable part is blocked. Remove the blocking object