Catalog LV 70 2011 - Low & Medium Voltage - Siemens

© Siemens AG 2011
Appendix
Glossary
Rated making capacity
(see also IEC/EN 60947-1; 4.3.5.2)
Rated operational current I e
(see also IEC/EN 60947-1; 4.3.2.3)
Rated operational voltage U e
(see also IEC/EN 60947-1; 4.3.1.1)
Rated power
(see also IEC/EN 60947-1; 4.3.2.3)
Rated service short-circuit breaking capacity I cs
(see also IEC/EN 60947-2; 4.3.5.2.2)
Rated short-circuit breaking capacity I cn
(see also IEC/EN 60947-1; 4.3.6.3)
Rated short-circuit making capacity I cm
(see also IEC/EN 60947-1; 4.3.6.2)
Rated short-time withstand current I cw
(see also IEC/EN 60947-1; 4.3.6.1)
Rated ultimate short-circuit breaking capacity I cu
(see also IEC/EN 60947-2; 4.3.5.2.1)
Rated uninterrupted current I u
(see also IEC/EN 60947-1; 4.3.2.4)
The value of current that an equipment is capable of switching on in
accordance with the utilization category and the rated operational
voltage.
The current that an equipment is capable of carrying, taking into
account the rated operational voltage, duration of operation, utilization
category and ambient temperature.
The voltage to which the characteristics of an equipment are referred.
The highest rated operational voltage must not be higher than the
rated insulation voltage.
The power output of a motor at the associated rated operational
voltage.
The prospective short-circuit current which, depending on the rated
operational voltage, a circuit breaker is capable of breaking repeatedly
(test cycle O-CO-CO, previously P-2). After interrupting this shortcircuit
current value, the circuit breaker must be capable of continuing
to carry and disconnect in the event of overloading, the rated uninterrupted
current, despite its own thermal level having increased.
The maximum value of current that an equipment is capable of switching
off at rated operational voltage and rated frequency, and without
sustaining damage. It is expressed as rms value.
The maximum value of current that an equipment is capable of switching
on at rated operational voltage and rated frequency, and without
sustaining damage. Unlike for other characteristic values, it is
expressed as maximum prospective peak value.
The short-time withstand current value that the equipment is capable of
carrying for a specified time without damage, e.g. due to excessive
heating.
Maximum short-circuit current which a circuit breaker is capable of
interrupting (test: O. CO, previously P-1). Following short-circuit switching
off, the circuit breaker is able, in the event of overload, to trip with
increased tolerances.
The value of current that an equipment can carry in uninterrupted duty
(for weeks, months or years).
Symbols used in technical data and formulae
OP ON period I T Response value of earth-fault release
I Δn Response value of earth-fault release I th Continuous free air thermal current
I cm Rated short-circuit making capacity I the Continuous thermal current of enclosed devices
I cn Rated short-circuit breaking capacity I u Rated uninterrupted current
I cs Rated service short-circuit breaking capacity S NT Transformer rating
I cu Rated ultimate short-circuit breaking capacity t r Delay time of overload release response
I cw Rated short-time withstand current t T Delay time of earth-fault release response
I e Rated operational current t v Delay time of short-circuit release response
i Transformer initial short-circuit current I rmf Response value of fixed, instantaneous short-circuit release
I L Response value for load monitoring I rmv Response value of short-time delayed short-circuit release
I n Rated current U c Rated actuating voltage
I NT Rated transformer current U e Rated operational voltage
I PK Rated impulse withstand current U i Rated insulation voltage
I q Rated conditional short-circuit current U im Rated impulse withstand voltage
I r Set value of overcurrent release u k Transformer short-circuit voltage
I rm Response value of instantaneous short-circuit release U s Rated control supply voltage
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