Troubleshooting and repair guide for DC contactor

1. The contacts have been closed but the iron core is still not fully closed, and there is vibration and noise.

(a) The power supply voltage is too low. Solution: Try to increase the voltage.
(b) The coil working voltage does not match the power supply voltage. The repair method is to replace the coil corresponding to the power supply voltage.
(c) The iron core is stuck due to mechanical reasons. The repair method is to adjust the position of the parts that are stuck to each other and remove the obstacle.
(d) The contact spring pressure and release spring pressure are too large. The repair method is to adjust the spring pressure or replace the spring.
(e) The contact overtravel is too large. The maintenance method is: adjust the contacts so that the overtravel of the contacts is less.

2. The contacts can’t close and no vibration and noise.

It is likely caused by a broken coil, which can be tested with a multimeter. The repair method is to find the breakpoint and to repair it. Or replace with a new coil.

3. The armature is not released or released slowly.

(a) The reaction force is too small. The maintenance method is to adjust the pressure of the spring or tension of the reaction spring.
(b) There is debris or oil contamination on the main contacts. Just wipe off the debris or oil contamination with a clean soft cloth.
(c) The mechanical moving part is stuck or the shaft is rusted or skewed. The maintenance method is to eliminate the jamming, remove and lubricate the rusted parts.
(d) The contacts have been welded together. The repair method is to open the welded contacts and replace them with new ones.
(e) The remanence is too large. For AC contactors, the E-shaped iron core will not be released due to the disappearance of the demagnetizing air gap after being used for a long time. The repair method is: you can file a part of the pole surface at the residual magnetic gap. If it does not work, replace the iron core; for DC contactors, replace or thicken the non-magnetic gasket to make it easier to release the armature after the coil loses power.

4. The coil is overheated or burned.

(a) The coil voltage is lower than the power supply voltage. The solution is to replace it with matching coil.
(b) The coil is damaged or leaks due to damp air or corrosive gas in the installation environment. The treatment method is to replace the special insulation coil and take measures to prevent moisture and corrosion.
(c) Interturn short circuit. The solution is to replace the coil.
(d) The operating frequency is too high. The solution is to extend the operation interval or replace the coil or contactor that is suitable for high operating frequencies.
(e) The armature is not fully pulled in, which causes the coil current to increase (this fault is accompanied by vibration and noise). The corresponding measures shall be taken according to the cause of the incomplete armature pull-in (refer to the repair method of No.1).
(f) The pole surface of the AC iron core is uneven or the residual magnetic air gap is too large, causing the coil to heat up. The repair method is to clean the pole surface or replace the iron core.
(g) The double-winding coil of the DC-operated electromagnet is stuck due to the long-closed auxiliary contact sticking, so that the starting winding is energized for a long time and generates heat. The repair method is to replace the self-locking contact and eliminate the cause of the contact welding.

5. Electric contact welding

(a) The operating frequency is too high or the product is overloaded. Solution is to replace the contactor with a larger rated current.
(b) The vibration is too severe during the closing process, and multiple vibrations occur. The heart treatment method is to find out the cause of the vibration (such as the voltage supplied by the coil is too low, causing the contact to vibrate and cause the contact to vibrate), and then take corresponding measures.
(c) The contact breaking capacity is insufficient, and the contacts are stuck after a short circuit on the load side occurs. The solution is to replace the contacts. The most thorough method is to use a contactor with a higher contact breaking capacity.
(d) Metal particles protrude on the contact surface. The maintenance method is to adjust the pressure of the contact spring.
(e) The contact spring pressure is too small. The maintenance method is to adjust the pressure of the contact spring.

6. Severe contact fever

(a) The load current is too large. The response method is to find out the cause of the excessive power. If this current is necessary, the large-capacity contactor should be replaced.
(b) The contacts are oily, dusty, or the copper contacts are severely oxidized. The repair method is to clean the contact surface.
(c) After the contact is severely ablated, the contact surface is greatly reduced, resulting in poor contact. The maintenance method is: use a fine file to trim carefully and restore the contact surface. If it cannot be restored, replace the new contact.
(d) The contact overtravel is too small, which makes the contact not tight. The treatment method is to adjust the overtravel. If the overtravel is reduced to half of the original, the contact should be replaced.

7. Contacts often wear out.

(a) There is a problem with the selection of the contactor. In the case of reverse braking or high-frequency operation, derating should be used. The treatment method is to use a high-capacity contactor or a contactor suitable for heavy tasks.
(b) The three-phase contact moves asynchronously. The maintenance method is to adjust the three-phase contacts to synchronization.
(c) The arc extinguishing system is faulty. The repair method is to replace the arc extinguishing cover.

8. The contactor is short-circuited between phases.

The reversible contactor chain is unreliable. Due to misoperation, two contactors are put into operation at the same time, which causes a short circuit between the phases, or because the contactor moves too fast, the conversion time is short, and an arc short circuit occurs during the conversion. Check the electrical and mechanical interlocks; change the contactor with a longer action time or extend the reverse conversion time.