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Appendix
Glossary
8/2
Siemens LV 36 · 2008
8
Rated operating voltage, (U
e
)
EN 60947-1; 4.3.1.1
Voltage fixed by the manufacturer. Several pertinent tests relate to its
determination, as may also the utilization category. Along with the
rated (operating) current, it determines the device’s utilization. The
highest value of rated operating voltage may in no case be greater
than the value of the rate insulation voltage U
i
.
Rated insulation voltage, (U
i
)
EN 60947-1; 4.3.1.2
Voltage measure to which are related tests of dielectric strength and
creepage distance.
Rated current, (I
n
)
EN 60947-2; 4.3.2.3
Current value of particular circuit breaker that can be handled uninter-
ruptedly. The highest current valued tripping the circuit breaker in
conformity with a specifically stated tripping characteristic.
Reduced rated current, (I
r
)
Specifically established, reduced value of
I
n
current for a regulated
time-dependent (thermal) release and that the circuit breaker can
handle continuously. Maximum setting is at value equal to
I
n
.
Changing
I
r
shifts the release’s tripping characteristic along the
current axis. (
I
r
= k x
I
n
holds where k
≤
1)
Tripping time at a given I
r
multiple, (t
r
)
Time after which circuit breaker will trip, if a current flows through it that
is equal to the given multiple of
I
r
. Changing t
r
shifts the tripping
characteristic along the time axis.
Actuating current of (selective) release’s
time-independent delay, (I
ds
)
Minimum current value causing the release’s time-independent delay
to actuate.
Delay of time-independent delayed release, (t
v
)
If a current flows through the circuit breaker equal to at least
I
sd
but not
reaching
I
rm
the circuit breaker will trip with time delay t
v
. Total shut-off
time is influenced by the tripping of the circuit breaker itself and is
about 10 ÷ 20 ms longer.
Actuating current of time-independent
instantaneous, (I
rm
)
Minimum current value causing the time-independent instantaneous
release to actuate.
Rated operating current, (I
e
)
EN 60947-1; 4.3.2.3
Rated operating current of device (switch-disconnector) is fixed by the
manufacturer with consideration for the rated operating voltage, rated
frequency, rated operation, utilization category and type of protective
cover, if that comes into consideration.
Rated normal current, (I
u
)
EN 60947-1; 4.3.2.4
Current value set by the manufacturer and which the device can
handle in continuous operation, i.e. during a period longer than 8 hours
(weeks, months, or longer).
Rated ultimate short-circuit breaking capacity, (I
cu
)
EN 60947-2; 2.15.1; 4.3.5.2.1
Ultimate short-circuit breaking capacity value expressed as the rms
value of the alternating component of the assumed short-circuit current
that the circuit breaker must be able to manage in the mode: 1x swit-
ching off of the short circuit and a following 1x make-break sequence.
After testing, the circuit breaker need not be able to conduct the rated
current uninterruptedly.
I
cu
is set for the rated operating voltage at the
rated frequency and at the established power factor for alternating
current or at the time constant for direct current. Must fulfil the
condition:
I
cu
≥
I
k
“
Rated short-circuit service breaking capacity, (I
cs
)
EN 60947-2; 2.15.2; 4.3.5.2.2
Value of the operating short-circuit breaking capacity expressed as the
rms value of the alternating component of the assumed short-circuit
current that the circuit breaker must be able to manage in the mode:
1x switching off of the short circuit and a following 2x make-break
sequence. May also be expressed as a percentage of
I
cu
. After
testing, the circuit breaker must be able uninterruptedly to conduct the
rated current and to switch off the overcurrent. Temperature increase
of the main terminals may be greater.
I
cs
is set for the rated operating
voltage at the rated frequency and at the established power factor for
alternating current or at the time constant for direct current. Permitted:
I
cs
≥
I
k
“
Rated short-time withstand current, (I
cw
)
EN 60947-1; 4.3.6.1
EN 60947-2; 4.3.5.4
EN 60947-3; 4.3.6.1
Value of short-time withstand current specified by the manufacturer
that the device is able to handle without damage during a designated
time period (short-time delay). In case of alternating current, it is the
rms value of the alternating component of the assumed short-circuit
current
I
p
.