Siemens SENTRON 3VL series - Page 61

Application planning
5.4 Use in DC systems
3VL IEC molded case circuit breakers
System Manual, 11/2013, 110 0110 - 02 DS 03
61
Example:
4000 A + 30% = 5200 A
There is also a tolerance of ± 20%
At the I
i
= 4000 A setting, the instantaneous short-circuit release responds at
approx. 5200 A ± 20%.
As the current has to flow through all of the conducting paths, the following connections are
recommended in order to satisfy the thermal tripping characteristics.
Recommended connections for DC systems
Table 5- 1 Recommended connections / maximum permitted DC voltage U
e
Circuit with 3-pole molded
case circuit breakers
Circuit with 4-pole molded case
circuit breakers
1)
≤ 250 V DC
Switching capacity N
≤ 500 V DC
Switching capacity H
2-pole switching (ungrounded system)
If there is no possibility of a ground fault, or if every
ground fault is rectified immediately (ground-fault
monitoring), then the maximum permitted DC voltage is
600 V for both circuits.
On an ungrounded system, all poles must be switched
off.
≤ 500 V DC
Switching capacity H
≤ 600 V DC
Switching capacity L
2-pole switching (grounded system
)
The grounded pole is always assigned to the individual
conducting path, so that there are always 2 conducting
paths in series in a circuit with 3-
pole circuit breakers in
the event of a ground fault and 3 conducting paths in
series in a circuit with 4-pole circuit breakers in the
event of a ground fault.
≤ 600 V DC
Switching capacity L
≤ 600 V DC
Switching capacity L
1-pole switching (grounded system)
1) With 4
conducting paths in series, either the 4th pole must be equipped with a 100% release, or the 4th pole (N) must be
equipped with neither an overload release nor a short-circuit release.
Recommended connections for DC systems with voltages of more than 600 V DC (e.g. photovoltaic
plants)
Detailed information on request.
Technical Support: http://www.siemens.com/lowvoltage/technical-support
(http://www.siemens.com/lowvoltage/technical-support
)