In: is the rated current of the overload release,
Ir: ? is the setting current of the long-time overload release,
Isd: It is the setting current of the short-time overload release.
Im: is the instantaneous (thermal magnetic) tripper setting current.
Ics: Rated operating short-circuit breaking capacity.
Icu: Rated ultimate short-circuit breaking capacity.
Io: serves as a base reference current for protection setting.
1. The rated current In of the release device refers to the maximum current that the release device can pass for a long time.
2. The operating current setting value Ir of the long-time overload release is: 1r=In for the fixed release, and Ir for the adjustable release is the multiple of the rated current 1n of the release, such as 1r=0.4～1×1n.
3. The short-delay electromagnetic release operating current setting value Im is a multiple of the overload release operating current setting value Ir. The multiple is fixed or adjustable, such as Im=2~10×Ir. For non-adjustable types, an appropriate setting value can be selected.
4. The operating current rating Im′ of the instantaneous electromagnetic release is a multiple of the rated current In of the release. The multiple is fixed or adjustable, such as Im′=1.5~11×In. For non-adjustable types, an appropriate setting value can be selected.
5. Rated ultimate short-circuit breaking capacity Icu: It is the value of the limit short-circuit breaking current under the specified test voltage and other specified conditions of the circuit breaker. It can be expressed in terms of expected short-circuit current. Extended information
The national standard "Low-voltage circuit breakers for low-voltage switchgear and control equipment" GBl4048.2-94 (equivalent to IEC947-2) explains the concept of rated current of circuit breakers as follows:
The rated current In of the circuit breaker refers to the current that the release can pass for a long time, which is the rated current of the release. For circuit breakers with an adjustable release, it is the maximum current that the release can pass for a long time.
Rated operating short-circuit breaking capacity Ics: refers to a breaking current value smaller than the rated limit short-circuit breaking current of the circuit breaker under the specified test voltage and other specified conditions. Ics is a percentage of Icu.
The rated short-time withstand current Icw refers to the current value that the circuit breaker can withstand for a short time under specified test conditions. For AC, this current value is the effective value of the periodic component of the expected short-circuit current, and the time related to the rated short-time withstand current is at least 0.05s
Baidu Encyclopedia - Rated operating short-circuit breaking capacity (Ics)
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