Maintenance of main contacts of magnetic contactor

Posted by Vitalina Sokol على

Maintenance of main contacts
If only the surface of the contact is rough and discolored, the contact is not damaged or completely worn at this time. In the picture below, the contacts look worse, but experience tells us that the contacts below are better than a new set. This is because the contacts are "electrically aligned" and the entire contact surface is in full contact. Based on this, it may be completely wrong to judge whether the contact needs to be replaced based only on the appearance of the contact surface.

Grinding contacts
Today, with the development of contact materials and the improvement of contactor performance, filing, grinding or other methods of trying to repair the contact or contact surface are not required. Based on past experience, doing so increases the risk of other problems. For example, the residue of sandpaper will increase the resistance of the contact and so on. Also in the process of trying to repair the contacts, failure to clean them can also affect the performance of the contactor. Contact maintenance should be limited to checking the wear of the contacts. This is to ensure trouble-free operation of the contactor until the next maintenance period. Checking the contacts can also determine whether the contactor is operating normally in the application and whether the contacts are abnormally worn or damaged.

In AC-3 applications, the contact appearance is in the case of a small number of contactor operations.

In AC-3 applications, the contacts are "good break-in".

Mechanical wear
The increase in the number of mechanical operations has a relatively small impact on the mechanical and electrical life of the contacts, but the following introductions to mechanical wear are also important.

Hum noise
If there is garbage on the surface of the iron core, the contactor will make a slight sound when the contactor is closed. It can be cleaned with a dry soft cloth. Hum noise can also be caused by deformation of the core surface. If the short-circuit ring on the iron core is damaged, the AC noise will be larger, because the magnetic field will cause the contactor to vibrate. If so, the contactor needs to be replaced. Another cause of AC noise may be corrosion caused by use in an environment that exceeds the technical specifications of the contactor. The contactor should be used in a non-condensing environment to avoid corrosion on the surface of the iron core.

Contact shake
The working voltage range of the coil of the contactor should be between 85% and 110% of the rated voltage. Contact wear is minimal with voltage fluctuations within +/-5%. If the voltage is too high, the speed of the iron core will be accelerated, and if the voltage is low, the speed of the suction will be reduced. All of the above factors will lead to higher contact vibration during pull-in. The high voltage and the speed of the pull-in will cause the sound of the pull-in to increase.

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