Under what circumstances are the contacts of the contactor prone to welding?

The main reasons why the contacts of the contactor are prone to welding include the following:
Excessive operation frequency or overloading of the product:
When the operating frequency of the contactor exceeds its designed range or the product remains in an overloaded state for a long time, the contacts will frequently open and close, causing the surface temperature of the contacts to rise and increasing the risk of welding.
Load-side short circuit:
If a short circuit occurs on the load side, the current will increase sharply, far exceeding the rated current of the contactor, causing the contacts to bear extremely high heat within a short period of time, thereby resulting in welding of the contacts.
Contact spring pressure is too low:
The contact spring is a crucial component that ensures the good contact and normal opening and closing of the contacts. If the spring pressure is too low, the contacts may not be able to make a tight contact when closing, resulting in an increase in contact resistance. This, in turn, leads to more heat generation when current passes through, increasing the possibility of welding.
The surface of the contact points is covered with metal particles or foreign objects:
If there are metal particles, oxides or other foreign substances on the contact surface, these substances may act as conductive bridges when the contacts close, resulting in an increase in local current density, generating a large amount of heat and causing welding.
Low voltage in the operation circuit or mechanical jamming:
If the voltage of the operating circuit is too low, it may result in insufficient suction force of the contactor, causing the contacts to stall during the closing process and remaining at the position where they just made contact. Moreover, if there is any jamming in the mechanical part, it will also affect the normal opening and closing of the contacts, increasing the risk of welding.
The main contact has been continuously passing through excessive current for a long time:
When the main contact continuously passes through a current exceeding its rated value for a long time, it will cause the contact to heat up severely. The prolonged high-temperature condition will cause the contact material to soften or even melt, and subsequently lead to welding phenomena.
In conclusion, the contacts of the AC contactor are prone to welding under conditions such as excessive operating frequency, short circuit on the load side, insufficient contact spring pressure, presence of metal particles or foreign substances on the contact surface, low operating circuit voltage or mechanical jamming, and long-term passage of overloading current through the main contact. To prevent this from happening, regular inspection and maintenance of the contactor are necessary to ensure it is in good working condition.