3WL Air Circuit Breakers
3WL Air Circuit Breakers/Non-Automatic Air Circuit Breakers up to 6300 A (AC)
General data
20
Siemens · 2009
Measurement method
Vectorial summation current formation (measurement method 1)
The three phase currents and the N conductor current are
measured directly.
The solid-state release determines the ground-fault current by
means of vectorial summation current formation for the three
phase currents and the N conductor current.
Direct measurement of the ground-fault current
(measurement method 2)
A standard current transformer with the following data is used for
measurement of the ground-fault current: 1200 A/1 A, Class 1
(the internal load of SENTRON 3WL is 0.11 Ω). The current trans-
former can be installed directly in the grounded neutral point of
a transformer.
3-pole circuit breakers, current transformers in the N conductor
3-pole circuit breakers, current transformers in the grounded neutral
point of the transformer
4-pole circuit breakers, current transformers in the grounded neutral
point of the transformer
Setting
How the module is set depends on the measurement method
used (see above):
Measurement method 1: in position .
Measurement method 2: in position .
This setting can be implemented for the solid-state release ver-
sion ETU76B with Menu/Comm.
Ground-fault protection with
I
2
t characteristic curve
With the exception of the ETU27B solid-state release, all
versions of the ground-fault modules are supplied with an
I
2
t
characteristic curve which can be activated.
Selection criteria for SENTRON 3WL circuit breakers
Basic criteria for selecting circuit breakers are:
• Max. short-circuit current
at place of installation of circuit brea-
ker
I ″
k max
.
This value determines the short-circuit breaking capacity
or short-circuit current carrying capacity of the circuit breaker.
• It is compared with the value
I
cu
, I
cs
, I
cw
of the circuit breaker
and essentially determines
the size of the circuit breaker.
See illustration "Overview of SENTRON 3WL Circuit
Breakers/Non-Automatic Air Circuit Breakers".
• Rated current
I
n
which is to flow through the branch circuit.
This value must not be larger than the maximum rated current
for the circuit breaker.
The rated current for the SENTRON 3WL is set with the rated
current module
.
See "Design", illustration "Overview of
SENTRON 3WL Circuit Breakers/Non-Automatic Air Circuit
Breakers".
• Ambient temperature
for the circuit breaker.
This is usually the control cabinet internal temperature.
•Design
of the circuit breaker
• Minimum short-circuit current
which flows through the switching device. The release must
still detect this value as a short-circuit and must respond by
tripping.
Protection functions
of the circuit breaker.
These are determined by the selection of the
corresponding solid-state release, see the table
"Functions of the solid-state releases" under "Functions".
NSE 00946
L1
L2
L3
N
PE
T5
SENTRON WL
NSE 00947
L1
L2
L3
N
PE
T6
SENTRON WL
NSE 00948
L1
L2
L3
N
PE
T6
SENTRON WL
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