Vacuum contactors are usually composed of insulation and isolation frame, metal base, transmission arm, electromagnetic system, auxiliary switch, vacuum switch tube and other components. When the electromagnetic coil passes the control voltage, the armature drives the arm to rotate, so that the main contact in the vacuum switch tube is connected. After the electromagnetic coil is powered off, the main contact is disconnected due to the action of the opening spring.

The vacuum interrupter has two functions ----reliable arc extinguishing when passing the normal working current and frequently cutting off the working current. But can not cut off overload current and short circuit current. The operating mechanism is composed of a holding coil with an iron core and an armature. When the coil is energized, the armature is attracted, and the contactor is closed; when the coil is de-energized, the contactor is disconnected. The holding coil generally has two forms: DC and AC.

The shell of the vacuum interrupter is made of ceramic insulating material, and the internal vacuum degree is usually above 0.01Pa. Since there is less air in the shell, the contact distance can be made very small, and the arc can be easily extinguished. The function of the shielding cover in the arc extinguishing chamber is to condense the metal vapor diffused from the contact gap when the current is interrupted, which helps to extinguish the arc, and also prevents the metal vapor from splashing onto the insulating shell to reduce its dielectric strength. The movable contact is connected with the lower end of the shell by a bellows, and the movable contact can move up and down without air leakage.