Circuit Breakers And Non-Automatic Circuit Breakers; Distinction Between Circuit Breakers And Non-Automatic Circuit Breakers - Siemens SENTRON 3WA Air Manual

Description

2.2 Circuit breakers and non-automatic circuit breakers

2.2 Circuit breakers and non-automatic circuit breakers
2.2.1

Distinction between circuit breakers and non-automatic circuit breakers

The 3WA can be used as a circuit breaker with electronic trip unit, but also as a non-automatic
circuit breaker according to IEC 60947-2.
Circuit breakers
The IEC 60947-2 standard applies to circuit breakers whose main contacts are designed for
connection to circuits with rated voltages up to 1000 V AC or 1500 V DC. According to IEC
60947-2, a circuit breaker is "a mechanical switching device, capable of making, carrying and
breaking currents under normal circuit conditions and also making, carrying for a specified
time and breaking currents under specified abnormal circuit conditions".
Non-automatic circuit breakers
Non-automatic circuit breakers have a rated conditional short-circuit current I
used as disconnectors, since the IEC 60947-2 standard also defines requirements for the
isolating function.
The 3WA non-automatic circuit breakers are tested according to IEC 60947-2 Annex L. Annex
L deals with circuit breakers which do not meet the requirements of overcurrent protection.
They are called circuit breaker interrupters (CBI). A CBI can be tripped with auxiliary releases,
e.g. shunt trips or undervoltage releases, also under short-circuit conditions, and is therefore
to be considered a higher-value device compared to switch disconnectors according to
IEC 60947-3, since switch disconnectors can disconnect at most the rated current.
A CBI is part of a circuit breaker series, being derived from the equivalent circuit breaker by
omitting the overcurrent release (type Y) or only the overload release (type X).
The following has been implemented for the 3WA non-automatic circuit breaker:
• Implementation of the circuit breaker without overcurrent release as CBI-Y
• The CBI-Y has an "isolating function", hence the name "non-automatic circuit breaker"
• The rated conditional short-circuit current I
circuit breaker over 0.5 s.
26
corresponds to the I
cc cw
Equipment Manual, 05/2021, 92310000002-03
and may be
cc
of the non-automatic
3WA Air Circuit Breakers