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Glossary
Glossary
Alarm switch
An auxiliary switch which operates only upon the tripping of the circuit
breaker with which it is associated.
Ambient air temperature
Temperature, determined under prescribed conditions, of the air surrounding
the complete switching device or fuse.
Anti-pumping device
A device which prevents reclosing after a close-open operation as long as the
device initiating closing is maintained in the position for closing.
Applied voltage (for a switching
device)
Voltage which exists across the terminals of a pole as a switching device just
before the making of the current.
NOTE: This definition applies to a single-pole device. For a multipole device it
is the phase-to-phase voltage across the supply terminals of the device.
Arcing contact
Arc contact on which the arc is intended to established.
Arcing time (of a multipole switching
device)
Interval of time between the instant of the first initiation of an arc and the
instant of final arc extinction in all poles.
Auxiliary contact
Contact included in an auxiliary circuit and mechanically operated by the
switching device.
Auxiliary switch (of a mechanical
switching device)
Switch containing one or more control and/or auxiliary contacts mechanically
operated by a switching device.
Backup protection
Overcurrent coordination of two overcurrent protective devices in series
where the protective device, generally but not necessarily on the supply side,
effects the overcurrent protection with or without the assistance of the other
protective device and prevents any excessive stress on the latter.
Breaking capacity (of a switching
device or a fuse)
Value of prospective breaking current that a switching device or a fuse is
capable of breaking at a stated voltage under prescribed conditions of use
and behavior.
Breaking current (of a switching device
or a fuse)
Current in a pole of a switching device or a fuse at the instant of initiation of
the arc during a breaking process.
Break time
Interval of time between the beginning of the opening time of a mechanical
switching device (or the pre-arcing time of a fuse) and the end of the arcing
time.
Circuit breaker
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 such as those of short- circuit.
Clearance
Distance between two conductive parts, along a string stretched the shortest
way between these conductive parts.
Closing time
Interval of time between the initiation of the closing operation and the instant
when the contacts touch in all poles.
Conditional short-circuit current
(of a circuit or a switching device)
Prospective current that a circuit or a switching device, protected by a
specified short- circuit protective device, can satisfactorily withstand for the
total operating time of that device under specified conditions of use and
behavior.
Conductive part
Part which is capable of conducting current although it may not necessarily
be used for carrying service current.
Control circuit (of a switching device)
All the conductive parts (other than the main circuit) of a switching device
which are included in a circuit used for the closing operation or opening
operation, or both, of the device.
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