Glossary
3KF switch disconnectors with fuses
Manual, 09/2019, L1V30580914002A-01
149
Rated short-circuit making capacity
The rated short-circuit making capacity I
cm
of a molded case circuit breaker is the maximum
current that the circuit breaker can safely close at a specific rated operational voltage and
rated frequency. Unlike other characteristic data, this is specified as a peak value. With AC
molded case circuit breakers, the rated short-circuit making capacity must be at least equal
to the rated short-circuit breaking capacity multiplied by a factor n. The rated short-circuit
making capacity is calculated to allow the molded case circuit breaker to conduct the current
during closing at a voltage of up to 110% inclusive of the rated operational voltage.
Rated short-time current
Permissible rms value of the AC component of the prospective short-circuit current that the
switching device is capable of conducting for a specific time period, e.g. from 0.05 s to 1 s
(thermal short-circuit strength).
Rated short-time withstand current
The rated short-time withstand current I
cw
is specified as an rms value of the short-circuit
current and characterizes the thermal strength of a circuit of a switchgear assembly under
brief load conditions. Calculation of the rated short-time withstand current usually refers to a
period of 1 s. If the reference period differs from that stated above, it must be specified. The
rated short-time withstand current is specified for the distribution and/or main busbars of a
switchgear assembly.
Rated ultimate short-circuit breaking capacity
The rated ultimate short-circuit breaking capacity Icu is the maximum short-circuit current
that the switch disconnector is capable of interrupting (test sequence 0 - C0, formerly P - 1).
The limit value of the rated ultimate short-circuit breaking capacity lcu: The rated ultimate
short-circuit breaking capacity Icu is the maximum short-circuit current that the protective
device is capable of interrupting according to regulations. Up to this value, the protective
device can also be used in a network.
Rated uninterrupted current
The rated uninterrupted current I
U
of a switching device, e.g. a molded case circuit breaker,
is the current that the device can conduct in uninterrupted operation (for weeks, months or
years). This current is specified by the manufacturer.
Short circuit
Connection with a negligibly low impedance between two points of different potential in an
electric circuit. The short-circuit current is a multiple of the rated operational current. Short
circuits can cause thermal or mechanical damage to switching devices and other parts of an
electrical installation.
Summary of Contents for SENTRON 3KF LV HRC
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Page 8: ...Table of contents 3KF switch disconnectors with fuses 6 Manual 09 2019 L1V30580914002A 01 ...
Page 110: ...Maintenance 3KF switch disconnectors with fuses 108 Manual 09 2019 L1V30580914002A 01 ...
Page 148: ...Conversion tables 3KF switch disconnectors with fuses 146 Manual 09 2019 L1V30580914002A 01 ...
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