Contactor Troubleshooting Guide

Regarding the issue of contactor failure, ATO.com has produced a guide for your reference

Short circuit of the contactor
Possible causes of the fault:

• The contactor works in the environment of damp, dust, steam, or corrosive gases.
• The arc chute damages or falls, load short leads to the contact short of the contactor.
• Incorrect operation of the positive and reverse contactor, as well as unreliable interlocking, make two contactors to pull in at a same time when reversing.

Maintenance method:

1. Improve the working environment and keep clean.
2. Match an arc-extinguishing equipment again.
3. Handle the load short failure.
4. Recheck the contactor's interlocking circuit, change the operation mode.

Fusion welding of the contactor due to electric shock
Possible causes of the fault:

• short circuit of contactor on the load side.
• Overload use of contactor contact.
• There’s a foreign body or a metal particle on the surface of the contact.
• Pressure of the contact spring is too small.
• Poor contact of contactor's lines, which makes the contactor repeatedly pull in and release at a moment.

Maintenance method:

1. Power off at first, separate the welding contacts with a screwdriver, correct the contact surface and eliminate the short-circuit fault.
2. Replace with a large capacity and high quality contactor.
3. Smooth the contact surface with a steel file and remove foreign bodies.
4. Readjust the spring pressure.
5. Check the bad contacts of the coil control loop of the contactor, reconnect the loop or replace electrical components, ensure a good on-off situation.

Iron core of the contactor can't suck up
Possible causes of the fault:

• Low power supply voltage.
• Something is wrong with the contactor's control loop or the power supply can't be connected.
• Contactor coil is broken or burned.
• The contactor magnet is partly inflexible or the moving contact gets stuck.
• Pressure of the contact spring is too large.

Maintenance method:

1. If there's a huge difference between the measured value and the coil's rated voltage, look up the reason from the power supply and adjust the voltage to the normal value.
2. Correct the contactor's control loop and connect it by the correct line; replaced the damaged electrical components.
3. Measure the coil resistance with a multimeter, if the current is too large, the coil shorts or breaks, please replace the coil.
4. Repair the mechanical fault of the contactor, remove the rusty part, add some lubricating oil to the movement mechanism; replaced the damaged electrical components.
5. Adjust the contact spring pressure according to technical requirements.

The contactor coil is overheated or burned down
Possible causes of the fault:

• Supply voltage is too high.
• Contactor is frequently operated.
• High ambient temperature, end face of the contactor's iron core is not smooth.
• There's a mechanical failure on the contactor's movable iron core, which makes the iron core unable to suck, turn-to-turn short circuit.

Maintenance method:

1. Measure whether the working voltage on the contactor conforms to the rated voltage of the contactor coil, if it's too high or too low, adjust it to the normal voltage value, or choose to replace the contactor that meets the rated voltage.
2. Improve the temperature of working environment, strengthen heat dissipation.
3. Clean and wipe the end face of contactor iron core, replace the iron core when necessary.
4. Check if the mechanical part of the contactor moves flexibly, replace a same type coil after repairing if the coil has been burned out.
5. Eliminate the reasons for causing mechanical damage of the contactor coil, replace the coil.

The contactor's iron core release slowly or can't be released
Possible causes of the fault:

• There’s oil dirt on the end surface of the contactor's iron core, which leads to slow release.
• Reaction spring damages that leads to slow release.
• Mechanical movement mechanism of the contactor's iron core gets stuck or rusty, which can't act flexibly.
• Fusion welding of contact makes the iron core unable to release.

Maintenance method:

1. Disassemble the contactor and take out the iron core, repeatedly wipe the end face of a good iron core with a rag, clean the oil dirt, then reassemble it.
2. Replace a new reaction spring.
3. Disassemble the contactor and check the cause for stuck, repair or replace damaged parts.Remove sundries and rust.
4. Separate the moving contact and static contact with a screwdriver, smooth the contact surface with an iron file, then find out the cause of fusion welding and make corresponding treatment.

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