Is to pull the arc, sub-section, Vauum interrupter contactor device is to prevent the contact when the arc spark caused by unnecessary losses caused by the set. In a high current circuit, the contact or switch off and forth will produce arc spark, may cause the following hazards: 1, burn contact contacts, etc., over time so that the circuit is bad, resulting in circuit damage. 2, may be on the human eye, skin and other arc burns caused by the human body can not be speculation of the harm. 3, in some places sensitive to arc spark, such as gas plant or filling the flammable gas where a little bit of the spark sparks may cause an explosion and so on. 4, the spark sparks may be with the circuit for some electronic products (such as integrated circuits) caused by breakdown damage. So for safety reasons, in a large current may cause contact contacts and other places have to install a metal box to shield the spark sparks, vacuum interrupter is the most common.