Contactor common faults and maintenance

Fault one: short circuit between contactors
Possible causes of failure
Contactor working in wet, dust, water vapor or corrosive gas environment causes short circuit; contactor arc extinguishing cover is damaged or fall off; load short circuit causes contactor contact short circuit at the same time; improper operation of positive and negative contactor, plus Chains and interlocks are not reliable, causing two contactors to pull at the same time when reversing.
Maintenance method
(1) Improve the working environment and keep it clean.
(2) Reconfigure the contactor arc extinguishing device.
(3) Deal with load short-circuit faults.
(4) Recheck the contactor interlock circuit and change the operation mode.
Fault II: contactor electric welding
Possible cause of failure
Contactor load side short circuit; contactor contact is overloaded; foreign matter or metal particle protrusion on the contact surface; contact spring pressure is too small; contactor circuit contact is bad, the contactor is instantaneously released several times.
2. Repair method
(1) Power off first, separate the welded contacts with a screwdriver, correct the contact surfaces, and eliminate short circuit faults.
(2) Replacement of high-quality contactors with a large capacity.
(3) Use a steel file to correct the contactor contact surface and clear foreign objects.
(4) Readjust the spring pressure.
(5) Check that the contactor coil control circuit is in poor contact, reconnect the circuit or replace the electrical component to make it turn on and off well.
Fault 3: The contactor core does not fit
Possible causes of failure
The power supply voltage is too low; the contactor control circuit is faulty or the power supply cannot be connected; the contactor coil is broken or burned out; the contactor magnet part is inflexible and the movable contact is stuck; the spring pressure of the hammer is too large.
Maintenance method
If the measured value is too different from the rated voltage of the coil, look for the cause from the power supply and adjust the voltage to the normal value.
Correct the control circuit of the contactor and connect it with the correct circuit; replace the damaged electrical components.
Use a multimeter to block the coil resistance when the coil of the contactor is broken. If the resistance of the coil is too large, the coil is short-circuited or broken, the coil should be replaced.
Repair the mechanical failure of the contactor, remove the rust, and add some lubricant to the mechanical action mechanism; replace the damaged electrical components.
According to the technical requirements, readjust the contact spring pressure.
Fault 4 Contactor Iron Core Releases Slowly or Does Not Release
Possible cause of failure
The contactor iron core surface has the grease to cause slow release; the reverse spring damage causes the release to be slow; the contactor iron core mechanical action mechanism is stuck or rust, the action is not flexible; the contactor contact welding can not release.
Fault repair methods and techniques
Remove the contactor, remove the moving iron core, wipe the end surface of the good iron core with a rag, wipe the grease, and reassemble it.
Replace the new reaction spring.
Disconnect the contactor, check the cause of the stuck mechanism, repair or replace the damaged parts; clear debris and rust removal.
Use screwdrivers to separate the static and dynamic contacts, and trim the contact surfaces with iron taper. After repair, find out the cause of welding and handle accordingly.
Fault 5 Overheated or burned contactor coil
Possible cause of failure
The power supply voltage is too high; the operation of the contactor is too frequent; the ambient temperature is too high; the end face of the contactor iron core is uneven; the moving core of the contactor has a mechanical failure, so that it cannot pull in after being energized, and short-circuit between turns.
Troubleshooting method
Measure whether the working voltage on the contactor matches the rated voltage of the contactor coil. If it is too high or too low, adjust it to the normal voltage value.
Improve the working environment temperature and enhance heat dissipation.
Clean the end face of the wiper contactor core and replace the core when it is severe.
Check whether the movement of the mechanical part of the contactor is flexible. If the coil is burned after the repair, replace the coil of the same type.
Remove the cause of mechanical damage to the contactor coil and replace the contactor coil.
Fault 6 The noise of the contactor when working
Possible causes of failure
Contactors work long in places where the ambient temperature is too high; operation is too frequent; the contact travel is too small; there is foreign matter or unevenness on the contact surfaces; the contact spring pressure is too low; three-phase contacts cannot be in synchronous contact; the load side is short-circuited.
Repair methods and techniques
Use a multimeter to measure whether the supply voltage of the contactor coil is lower than the required rated voltage. If it is too low, find the cause on the line and adjust the voltage to the normal value.
Grind the suction end face of the contactor with fine sandpaper to remove impurities, apply a little oil on the end face than necessary, and reassemble.
Reassemble and repair the contactor action mechanism.
Solder the shorting ring and reconnect it.
Replace the contactor core.
Re-adjust the contactor spring pressure to make it fit.