Maintenance of AC contactor coil
I believe everyone knows about the AC contactor. The biggest failure of the AC contactor is its coil, so today Sofielec has collected relevant information and summarized it. I sincerely hope that it can help you.
Ⅰ. Judgment method when the coil is abnormal
Coil burnout is sometimes caused by a combination of multiple factors, and it is often difficult to judge the burnout situation with the naked eye. Generally, after an abnormality occurs, it is necessary to record the occurrence and conduct on-site investigations. Here are a few typical situations.
Short-term (within a few minutes) burned coil
This type of burn is usually caused by misreading the rated voltage of the coil and applying a double voltage.
It can be seen that the center of the (SC-03~N5A) coil is raised, a large amount of molten magnet wire sheath overflows the coil bobbin, and the square hole in the center of the coil has the bobbin material dissolving inward.
Long-term (above tens of minutes) AC contactor coils that have been burnt
This type of burn is usually caused by a significant voltage drop (below 85% voltage), the AC contactor is in an open state, and undervoltage is applied.
It can be seen that the center of the coil (SC-03~N5A) bulges, the melt of the magnet wire sheath overflows into a spherical shape, the magnet wire is slightly discolored, and sometimes the square hole in the center of the coil will have the skeleton material eluted inward.
Ⅱ. Causes of coil burnout
When conditions such as use conditions and environmental negative pressure become more stringent, it will accelerate the aging of the coil.
So, what are the main reasons for the reduction of coil life/burnout?
Poor connection
If the power supply voltage drops or foreign objects are caught and the solenoid is not fully attracted, the excitation inrush current (10-15 times the holding current) will flow through the coil, which will cause the coil to burn out.
Overvoltage
When the voltage applied to the coil is too high and the excitation current increases, the life of the coil will be shortened. Moreover, when the voltage is extremely high, the coil may be burned out.
Wrong use of voltage and frequency
When the rated voltage of the coil is different from the power supply voltage, no matter how high or low the difference is, it may cause the coil to burn out.
Excessive switching frequency
Using it at a switching frequency higher than the specified frequency may cause burnout.
close installation
In the case of continuous energization, when the AC contactor installed in parallel is used, the coil temperature in the center part is the highest, and the thermal aging is the most serious.
Tremor
If the operating contact bounces or the coil terminal is loose and causes the contact to vibrate violently, the starting current will flow in the coil, which will cause the coil to burn.
