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Siemens · 10/2014
3WL Air Circuit Breakers
3WL air circuit breakers/non-automatic air circuit breakers up to 6300 A (AC), IEC
Project planning aids
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Characteristic curves
2)
Every electronic trip unit type and every setting has its own
characteristic curve. Only a selection is shown in the following.
The characteristic curves each show the largest and smallest
setting range of 3WL circuit breakers with 1000 A rated current
at 500 V rated voltage with various trip units. In order to obtain
a complete tripping characteristic, the relevant parts of the
characteristics have to be combined. The characteristic curves
show the behavior of the electronic trip unit when it is activated
by a current that is already flowing before the tripping operation.
If the overcurrent tripping occurs immediately after closing and
the electronic trip unit is therefore not yet activated, the opening
time is extended, depending on the level of the overcurrent by
up to 15 ms. To determine the break-times of the circuit
breakers, approximately 15 ms must be added to the opening
times shown for the arcing time.
Refer to the following legend for tolerances.
The characteristic curves shown apply to ambient temperatures
at the circuit breaker between –5 and +55°C. The trip unit can be
operated at ambient temperatures of –20 to +70°C. An extended
tolerance band can apply at these temperatures.
3WL circuit breaker with ETU25B electronic trip unit,
LSI characteristic curve
3WL circuit breaker with ETU27B electronic trip unit,
G characteristic curve
Tolerances for the current settings
L: tripping operations between 1.05 and 1.2 x I
R
S: –0 %, +20 %
I: –0 %, +20 %
G: –0 %, +20 %
Tolerances for the tripping times
L: –20 %, +0 % for I
2
t characteristic curve
S: –0 %, +60 ms or -0 %, 10 % for tripping times greater than 600 ms
I: <50 ms
G: –0 %, +60 ms or -0 %, 10 % for tripping times greater than 600 ms
3WL circuit breaker with ETU15B electronic trip unit
3WL circuit breaker with ETU27B electronic trip unit,
LSIN characteristic curve
3WL circuit breaker with ETU45B electronic trip unit,
S characteristic curve
1)
Sizes I and II: 100 ... 1200 A
Size III: 400 ... 1200 A
2)
With a single-pole load in the lowest rated current range, the response
times of the short-circuit trip can increase by approx. 10 % and the tripping
times by approx. 15 % with respect to the characteristic curve.
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