ABB Maintenance of contacts

Maintenance of contacts

A contact is not necessarily damaged or worn out, just because the surface is rough and

discolored. The contacts in the figure below may look like bad contacts but the fact is

that they are better than a new set of contacts. This is because they are ”electrically sea

ted” and make good contact over a larger surface. Based on this it would be completely

wrong to change a contact only by judging from the appearance of the surface. Also it

is quite normal that the contacts in the three phases are not evenly worn and because

of this all contacts both fixed and movable need to be changed. At the same time it is

recommended to change the arc chutes.

Inspection of contacts

With today´s high performance contactors, filing, grinding, or other attempts to restore

contacts or contact surfaces should be avoided. Our experience shows that filing and

grinding increases the risk of causing other problems. For example the risk of increasing

the contacts resistance  is high due to scrap from this grinding and filing.

Maintenance should be limited to inspection of the contacts for the level of contact wear.

This is to ensure a trouble free operation of the contactor until the next service is requi

red (see next section –Interpreting levels of electrical contact wear). At the same time

observations can be made to judge if the contactor operates well in the application and

that no signs of abnormal wear or damages are present on the contacts.