A contactor is a switching device that utilizes electromagnetic, pneumatic, or hydraulic principles to control the opening and closing of a main circuit. Widely applied in fields such as industrial automation and new energy vehicles, it primarily serves to control power loads such as electric motors and welding machines. Characterized by high current-breaking capacity, rapid operation, and remote control capabilities, contactors are frequently used in conjunction with fuses. Based on their actuation method, they can be classified into types such as electromagnetic and permanent magnet; based on the arc-extinguishing medium used, they are categorized into types such as air-break and vacuum.
A contactor consists of an electromagnetic mechanism, a contact system, and an arc-extinguishing device; when the coil is energized, it generates a magnetic force that drives the contacts to close. Newer hybrid DC contactors employ anti-parallel thyristors to achieve arc-free interruption, while permanent magnet operating mechanisms are powered by energy-storage capacitors to reduce energy consumption. Smart contactors feature autonomous interruption protection and reset functions, and their multi-layer insulation design enhances safety in high-voltage environments. The national standard GB/T 14048.4-2020 specifies various utilization categories-such as AC-3 and AC-4-along with their corresponding overload multiples.
