In modern industry, electric motors are used to drive power units. Basically, these are asynchronous three-phase machines that consume a lot of current at the time of starting. Therefore, electromagnetic contactors or starters are used to start them.
These devices have movable, powerful contacts, which are pressed against the fixed ones under the action of an electromagnet, forming a kind of "bridge" for an electric current. At the moment of closure, an electric arc is formed in the gap, which can melt the metal.
To prevent this from happening, several mechanisms are provided in the contactor:
- The force of attraction of the electromagnet must be sufficient to overcome the arc force.
- The contacts must have sufficient contact area, mechanical strength and high conductivity.
- In the contactor case, arc-extinguishing chambers are made of metal plates.
But, despite these factors, in the process of work, the contacts burn out. Periodic control and elimination of these phenomena is the main measure for contactor maintenance.
Small starters and contactors do not provide for the removal and cleaning of contacts, this is due to their low cost. As they wear out, they are replaced with new ones. Large contactors have a removable housing part and easy removal of the contacts for maintenance. This article covers service using a Chinese 400 amp contactor.
1. The removable part of the case is removed, depending on the design, it can be on screws or spring latches.
2. Moving contacts are dismantled, they can also be structurally different for different models of contactors.
3. Movable and fixed contact pads are cleaned with fine-grained emery paper.
4. Replacing the contacts and assembling the case.
As practice shows, the timely execution of such a simple work significantly prolongs the operation of the apparatus and minimizes emergency situations in electrical installations.