Circuit breaker refers to a switching device that can close, carry and break current under normal circuit conditions and close, carry and break current under abnormal circuit conditions within a specified time. Circuit breakers are divided into high-voltage circuit breakers and low-voltage circuit breakers according to the scope of application. The boundary between high voltage and low voltage is vague, and those above 3kV are generally called high voltage appliances.
Circuit breakers are generally composed of contact system, arc extinguishing system, operating mechanism, release and shell.
During short circuit, the magnetic field generated by large current (generally 10 to 12 times) overcomes the reaction spring, and the release pulls the operating mechanism to act, and the switch trips instantly. When overloaded, the current becomes larger, the calorific value intensifies, and the bimetal deforms to a certain extent to push the mechanism to move (the larger the current, the shorter the action time).
If it is electronic, the magnitude of each phase current is collected by transformer and compared with the set value. When the current is abnormal, the microprocessor sends a signal to make the electronic release drive the operating mechanism to act.
The function of circuit breaker is to cut off and connect the load circuit, cut off the fault circuit, prevent the accident from expanding and ensure the safe operation. The high-voltage circuit breaker will break the arcs with currents of 1500V and 1500-2000A, and these arcs can be stretched to 2m and continue to burn.
Extended data:
The rated limit short circuit breaking capacity and rated operating short circuit breaking capacity of the circuit breaker are as follows:
1, rated limit short-circuit breaking capacity of the circuit breaker: according to the conditions specified in the specified test procedure, the breaking capacity of the circuit breaker to continue carrying its rated current capacity is excluded;
2. Rated short-circuit breaking capacity of the circuit breaker: according to the conditions specified in the specified test procedure, including the breaking capacity of the circuit breaker to continue carrying its rated current;
3. The test procedure of rated limit short circuit breaking capacity is O-T-Co.
4. The test procedure for rated operating short circuit breaking capacity (Icn) of circuit breakers is O-T-Co-T-Co. It has one more Co than Icn's test program. After the test, the circuit breaker can completely break and extinguish the arc, so it is considered that its rated short-circuit breaking ability is qualified.
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