Specifications

5
COMPACT
®
NS circuit breaker
Circuit breaker current limiting capacity
The limiting capacity of a circuit breaker is its ability to
limit short-circuit currents.
Exceptional current limiting capacity
The exceptional limiting capacity of the COMPACT
®
NS line is due to the double
break technique (very rapid natural repulsion of contacts and the appearance of two
arc voltages in series with a very steep wavefront).
The exceptional limiting capacity of the COMPACT
®
NS line greatly reduces the
forces created by fault currents in devices. The result is a major increase in breaking
performance. In particular, the service breaking capacity Ics is equal to 100% of Icu.
The Ics value, defined by IEC 947-2, is guaranteed by tests comprising the following
operations:
■ Breaking a fault current equal to 100% of Icu three times consecutively;
■ Checking that the device continues to function normally:
❑ Conduction of rated current without abnormal temperature rise,
❑ Protection functions perform within the limits specified by the standard,
❑ Suitability for isolation is not impaired.
Longer service life of electrical installations
E28801
Current limiting circuit breakers greatly reduce the negative effects of short circuits
on installations.
Thermal effects
Less temperature rise in conductors, therefore longer service life for cables.
Mechanical effects
Reduced electrodynamic forces, therefore less risk of electrical contacts or busbars
being distorted or broken.
Electromagnetic effects
Less disturbance for measuring devices located near electrical circuits.
General characteristics
COMPACT
®
NS circuit breaker: functions and characteristics
prospective
Isc
Isc
t
limited
Isc peak
limited
Isc
tsc
prospective
Isc peak
actual
current
prospective
current