Main Features Of Circuit Breaker

The main characteristics of the circuit breaker are: rated voltage Ue; rated current In; tripping current setting range of overload protection (Ir or Irth) and short-circuit protection (Im); rated short-circuit breaking current (industrial circuit breaker Icu; household circuit breaker Icn )wait.
Rated operating voltage (Ue): This is the voltage at which the circuit breaker operates under normal (uninterrupted) conditions.
Rated current (In): This is the maximum current value that a circuit breaker equipped with a special overcurrent trip relay can withstand indefinitely at the ambient temperature specified by the manufacturer. It will not exceed the temperature limit specified by the current-bearing component.
Short-circuit relay tripping current setting value (Im): The short-circuit tripping relay (instantaneous or short delay) is used to trip the circuit breaker quickly when a high fault current value occurs, and its trip limit is Im.
Rated short-circuit breaking capacity (Icu or Icn): The rated short-circuit breaking current of a circuit breaker is the highest (expected) current value that the circuit breaker can break without being damaged. The current values provided in the standard are the root mean square value of the AC component of the fault current. The DC transient component (which always occurs in the worst case short circuit) is assumed to be zero when calculating the standard value. Industrial circuit breaker ratings (Icu) and household circuit breaker ratings (Icn) are usually given in terms of kA rms values.
Short-circuit breaking capacity (Ics): The rated breaking capacity of the circuit breaker is divided into two types: rated limit short-circuit breaking capacity and rated operating short-circuit breaking capacity. The national standard "Low-voltage circuit breakers for low-voltage switchgear and control equipment" (GB14048.2-94) explains the rated limit short-circuit breaking capacity and rated operating short-circuit breaking capacity of circuit breakers as follows:
1. The rated limit short-circuit breaking capacity of the circuit breaker: according to the conditions specified in the prescribed experimental procedures, excluding the breaking capacity of the circuit breaker that continues to carry its rated current capacity;
2. The rated operating short-circuit breaking capacity of the circuit breaker: according to the conditions specified in the prescribed experimental procedures, including the breaking capacity of the circuit breaker that continues to carry its rated current capacity;
3. The test procedure for rated limit short-circuit breaking capacity is O-t-CO.
The specific test is: adjust the current of the line to the expected short-circuit current value (for example, 380V, 50kA), but the test button is not closed, and the circuit breaker under test is in the closed position. Press the test button, and the circuit breaker passes 50kA short-circuit current. The circuit breaker opens immediately (open is referred to as O). The circuit breaker should be intact and can be closed again. t is the intermittent time, usually 3 minutes. At this time, the line is still in the hot standby state. The circuit breaker is connected again (close is referred to as C) and then disconnected (O). (The connection test is to assess the peak value of the circuit breaker. electrodynamic and thermal stability under current). This procedure is CO. If the circuit breaker can completely break, its ultimate short-circuit breaking capacity is qualified.
4. The test procedure for the rated operating short-circuit breaking capacity (Icn) of the circuit breaker is O-t-CO-t-CO. It has one more CO test procedure than Icn. After testing, if the circuit breaker can completely break and extinguish the arc, it is deemed that its rated operating short-circuit breaking capacity is qualified.
Therefore, it can be seen that the rated limit short-circuit breaking capacity Icn refers to the fact that the low-voltage circuit breaker can operate normally after breaking the maximum three-phase short-circuit current at the outlet end of the circuit breaker and break the short-circuit current again. As for whether it can operate normally in the future The circuit breaker does not guarantee the making and breaking of the circuit breaker; the rated operating short-circuit breaking capacity Ics refers to the fact that the circuit breaker can break normally multiple times when the maximum three-phase short-circuit current at its outlet end occurs.