How To Prevent Contactor From Burning Out

The trademark of modern contactors is their reliability as the technology of contactors has been refined over many years. If the contactor is used within its defined operating parameters, an anticipated performance can be expected. If the contactor is subject to stress outside its ratings, failure will take place. As with any electrical equipment, the key points in ensuring optimal performance in its service life lie in the correct installation, appropriate use during the process, and timely maintenance. Let’s elaborate on these below. 

Prior to installation,

1. Ensure the operating voltage of the application and the rated voltage of the contactor’s coil are compatible. Both over-voltage and voltage drop will affect the durability of the coil and eventually cause burnout to the coil.
2. Use a dry cloth to clean off any anti-rust grease. For the rust scale above the iron core, use gasoline.
3. Ensure the ambient temperature around the contactor is maintained within specified levels and avoid any hot spots, as contactors are generally energised for very long periods of time.

During installation,

4. Generally, for vertical installation, the tilt angle must be less than 5 degrees; otherwise, the performance of the contactor will be affected.

5. When connecting the wires, do not leave any metal parts exposed. This is to avoid oxidation. Tighten the screws to avoid poor wire contact due to vibration. Schneider Everlink has excellent tightening technology. The Everlink fixing system ensures fixing without creep, as well as reduced heat loss at the connection points.

6. Clean up any loose finely broken wires. This is to avoid any wire falling into the contactor’s Sewell which will cause blockage in contactors and result in the burning of the coil.

7. Ensure the upper and lower sides of the hole are conducive to heat dissipation.

In general, the maintenance of AC contactor is divided into run-time maintenance and inactive maintenance, as described below:

1. Run-time maintenance

During normal use, (a) Ensure the load current is within the normal range. (b) Ensure the relevant indicators conform to the normal circuit indicators. (c) Look out for any abnormal sound, like chatter, humming, or buzzing during operation and as noise is an indication of poor contact or under-voltage.  (d) Ensure no discoloration at the contact points and that the coil is not burned out. (e) Keep the contactor clean, both inside and outside. Refrain from having a poor operating state in the surrounding environment, which includes keeping away from the moisture, dust, oil, and physical obstruction that affects the full closure of the contactor and limit the degree of vibration.

2. Inactive maintenance

(a) Ensure the cable is secure, the wire insulation is not damaged, and refrains from having any loose ends. If the contact is loose, look out for any traces of burns.

(b) Ensure strict measurement of the interphase insulation resistance of AC contactors, and the resistance value is not less than 10MΩ.

(c) Clean the contactors regularly.  

(d) For the maintenance of the contact system, Ensure the reliability of the contact, the endurance of the coil, and the function of the middle spring.
Check if the contactor coil is open weld, burnt, and/or discoloured. 
(e) For the maintenance of the iron core Ensure the iron core is removed when conducting a power failure inspection.
General inspection includes, 

(i) Look out for any abnormal sounds.

(ii) Check if the short circuit ring is damaged. Replace any damaged rings timely if necessary.