The role of the circuit breaker is switched off and on the load circuit, and cut off the fault circuit to prevent the accident and to ensure safe operation. The high voltage circuit breaker to breaking 1500V, current 1500-2000A arc, which can stretch to 2m arc still continue to burn is not extinguished. Therefore, high-voltage circuit breaker interrupter is a problem that must be addressed. Blowing arc extinguishing the arc principle is weakened cooling heat free, on the other hand by the blow-out elongated arc reinforced composites and diffusion of charged particles, while the charged particles blown arc gap, rapid recovery of the dielectric strength of the medium. Voltage circuit breakers, also known as automatic air switch, used to making and breaking the load circuit can also be used to control infrequent start motor. It functions as a knife switch, part of the total sum of the function or electrical overcurrent relays, loss of pressure relays, thermal relays and leakage protection, etc., is low-voltage distribution network is an important protective device. Voltage circuit breaker with a variety of protection functions (overload, short circuit, under-voltage protection, etc.), the action is adjustable, high breaking capacity, easy operation, safety, etc., so now widely used. Structure and working principle by the low voltage circuit breaker operating mechanism, contacts, protection devices (various releases), extinguishing system components. Low voltage circuit breaker main contact is by manual or electric closing. After the primary contact closure, trip-free mechanism will lock the main contact in the closing position. Overcurrent release coils and heat release of the heating element in series with the main circuit, undervoltage release coil and power supplies in parallel. When the circuit is short circuit or severe overload, over-current release of the armature pull the free trip mechanism is operated, the main contact disconnect the main circuit. When the circuit is overloaded, the thermal element of the thermal release of heat bending the bimetal, promote free trip action. When the circuit is under voltage, under voltage release of the armature released. Also free trip action. Shunt release is used as a remote control, in normal operation, the coil is de-energized when required distance control, press the start button, the coil is energized, the armature drive free trip action, the main contact point disconnected.