How to Repair AC Contactors?

Inspection of AC contactor in operation

Whether the load current within the rated current of the the contactor.
Whether the contactor’s connection/ disconnection signal indicator is consistent with the circuit state.
Whether the running sound is normal, is there a electroacoustics caused by poor contact;
Whether the electromagnetic coil is overheated, is there any abnormality in the short circuit ring of the electromagnet.
Whether the arc extinguisher is loosen or damaged.
Whether the auxiliary contacts is burned out.
Whether the transmission part is damaged.
Whether there are unfavourable operating factors in the surrounding environment, such as excessive vibration, bad ventilation, too much dust.

AC contactor maintenance
The ac contactor shall also be maintained as the electrical equipment is maintained.
1. External maintenance

Clean out the outside dust.
Check whether the fasteners are loose, particularly the conductor connection parts, prevent heating from contact loosening.

2. Contact system maintenance

Check whether the position of the movable and static contact points is aligned, whether the three-phase is closed at the same time; Adjust the contact spring in case of any problem.
Check the wear degree of contact points, the wearing depth shall not be more than 1mm. In case of contact burning or welding falling, please replace timely; Slight burning will not affect the application. The sand paper can not be used to clean the contact, a shaping file is suitable.
The resistance shall not be less than 10MΩ when measuring the interphase insulation resistance;
Check whether the auxiliary contact acts flexibly, the contact travel should comply with the specified value. Check whether the contact is loosening, maintain or replace timely in case of any problem.

3. Iron Core Maintenance

Clean the dust, especially those between moving parts and contact surface of the iron core.
Check the tightness of the iron core, loose iron core will increase the running noise.
Repair timely when the short-circuit ring of the iron core falls off or breaks.
Maintenance of electromagnetic coil

4. Measure the insulation resistance of the coil.

Check whether the coil insulation has the phenomenon of discoloration and aging, surface temperature of the coil shall not exceed 65℃.
Check the lead connection of the coil, repair timely if the welding breaks or burns.

5. Maintenance of Arc Extinguisher