Maintenance of electromagnetic contactors

After installing the contactor, before connecting it to the network, it is necessary to remove grease from the working surfaces of the armature and the core with a clean cloth soaked in gasoline, and check the voltage correspondence of the main circuit and control circuit according to the table data. Compliance with the design of the type and rating of the contactor and the integrity of all electrical connections are also checked.

In addition, you should make sure that the contactor adjustment is not disturbed, for which it is necessary: ​​check that all moving parts of the contactor (including the auxiliary contact assemblies) are not stuck, several times slowly by moving them by hand until the contactor is switched on (without cameras and with cameras), firmly fix the wires connected to the coil of the contactor retractor, check the correct switching on of the contactor according to the diagram, tighten all the clamping screws and nuts until failure, by two or three remote switching on and off of the contactor without current in the main circuit, check the clarity of its operation and eliminate the detected defects, check the compliance of the solutions and dips and pressure of the main contacts ratings of contactors.

In the operating conditions of electromagnetic contactors, it is necessary to regularly monitor the condition of the contactors. The main parameters of a contact device are contact solution, contact failure and contact pressure. That is why they are subject to mandatory periodic checks, adjustments and corrections.

Under normal conditions, the electromagnetic contactor should be checked after 50 thousand operations, and contactors with a locking mechanism - after every 2 thousand operations, but at least once a month. Nevertheless, the contactor check should be carried out after each tripping of the fault current.

Before starting to check the contactor, it must be disconnected from the mains.All nuts must be tightened, the contactors (assemblies and parts) must be cleaned of dust, dirt, soot and corrosion, the contacts must be wiped with a dry cloth, and in the presence of carbon deposits - with a cloth soaked in gasoline. The contact surfaces of the contactors when sagging and solidified drops of copper (beads) appear on the contacts, darkening from overheating is cleaned with a slightly fine glass (but not sandpaper) paper or a velvet file. In this case, it is necessary to remove as little metal as possible and not change the profile of the contact. It is also necessary to clean the horns and walls inside the chamber. It is forbidden to clean the contacts with sandpaper linen, as sandpaper crystals cut on copper and deterioration of the contact.

The contacts must always be dry, lubrication of the surfaces is not allowed, as it burns from the arc and contaminates the contact surfaces with combustion products, as a result of which the heating of the contacts increases and conditions for their welding are created.

When cleaning the contact surfaces, it is necessary to strictly preserve the original shape (profile, radius of curvature) of the contacts in order to maintain the necessary rolling of the contacts, to protect them and not to abuse the cleaning, removing only drops and sagging , until the surface is level, not until the shells are removed. After feeding, the contacts should be wiped with a clean cloth. Polishing of the contact surfaces is not required as it gives greater contact resistance than filing.

Continuous contactors are manufactured with silver lined contacts.The use of silver is due to the fact that copper contacts oxidize during continuous operation and do not conduct current well. Silver contacts are not processed with a file, but are rubbed with chamois if they burn. If the silver lining is worn and copper will appear where the contacts touch, such a contact should be replaced.

The contacts must touch linearly across the entire width without gaps, both at the time of initial contact and in the on position. When switching on the contactor, the contacts should touch first with the upper and then with the lower parts, gradually rolling with a slight slide, which keeps their surface in good condition. When switching off, the process must be carried out in reverse order.

The correctness of the installation of the interrupting contacts is checked with a thin tissue or carbon paper placed between the contacts before they are closed. I have on multi-pole contactors, check the simultaneous closing of the contacts of all poles.

When switched on, the contacts should close clearly without jumping (rattling). The ease of movement of the contactor is checked by turning it on by hand (without power). Any jamming must be removed. The contactor should be clearly turned on without steps and noticeable delay.

It is necessary to check the correctness of the mechanical blocking, which should not prevent the free and complete inclusion of one of the blocked contactors (incomplete activation of the contactor leads to overheating of the contacts and the coil, which may burn).

When one of the contactors is fully turned on, it is necessary to check the impossibility of turning on the other.Between the main contacts of one of the contactors at the time of initial contact of the main contacts of the other contactor there must be a gap of at least 1/4 of the contact hole.

Replacement of contactor main contacts after wear

The replacement of the main contacts made with pads is carried out after the thickness of the lining v is reduced by 80 — 90% of the original. The replacement of the main contacts made of copper should be done after the thickness has decreased by 50% of the original thickness. The service life of the contacts depends on the operating mode of the contactor and the load parameters.

After installing new contacts, it is necessary to adjust their position so that the contact is on a line whose total length is at least 75% of the width of the movable contact. The displacement of contacts in width is permissible up to 1 mm. After the revision of the contact system, it is necessary to install and repair arc chutes, check that there are no stuck moving contacts in them. Operation of the contactor with the arc chutes removed is not allowed.