Schneider MCCB complete model NSX-100 / 3P NSX circuit breakers generally consists of the contact system, arc system, operating mechanism, releases, such as Shell. When a short circuit, the magnetic field large current (typically 10 to 12 times) to generate a reaction force overcomes the spring, NSX circuit breaker (FIG. 1) releases the pulling operation mechanism is operated, the instantaneous trip switch. When the overload current becomes large, the heat intensifies, bimetal deformed to a certain extent, promote institutional action (current increases, shorter operating time). There are electronic type, the use of the phase current transformers collection size, compared with the set value, the microprocessor when the current abnormal signals that drive the electronic trip unit operating agency action. The role of the circuit breaker is turned off and the load circuit, and cut off the fault circuit to prevent the accident and ensure safe operation. The high voltage circuit breaker to open off 1500V, current 1500-2000A arc, which can stretch the arc continues to burn is not extinguished 2m. It is the high voltage circuit breaker interrupter must be addressed. Blowing arc extinguishing the arc principle is cooling reduced heat free, on the other hand by blowing elongated arc arc reinforced composite and diffusion of charged particles, while the arc gap of charged particles disperse quickly to restore 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 or all of the functions sum of electrical overcurrent relays, loss of pressure relays, thermal relays and leakage protection, etc., is an important low-voltage distribution network protection appliances. With a variety of low-voltage circuit breaker protection (overload, short-circuit, under-voltage protection, etc.), the action is adjustable, the circuit breaker (Figure 2) high breaking capacity, ease of operation, safety, etc., so now widely used. Structure and working principle voltage circuit breakers by the operating mechanism, contacts, protection devices (all releases), extinguishing system components. Low-voltage circuit breaker main contact is by manual or electric closing. After the main contact is closed, trip-free mechanism will lock the main contact in the closing position. Overcurrent trip coil and heat release of the heating element in series with the main circuit, undervoltage release coil and power in parallel. When the circuit is shorted or severe overload, overcurrent release armature pull, so that free trip action, the main contact disconnect the main circuit. When the circuit is overloaded, heating elements heat release of heat bending the bimetal to promote free trip action. When the circuit under-voltage, under-voltage release armature released. Also free trip action. Shunt trip 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 driven free trip action, the main contact off point. List NSX MCCB models; NSX100N / 3P NSX100N / 4P NSX100H / 3P NSX100H / 4P NSX160N / 3P NSX160N / 4P NSX160H / 3P NSX160H / 4P NSX250N / 3P NSX250N / 4P NSX250H / 3P NSX250H / 4P NSX400N / 3P NSX400N / 4P NSX400H / 3P NSX400H / 4P NSX630N / 3P NSX630N / 4P NSX630H / 3P NSX630H / 4P