Siemens SINAMICS S120 Equipment Manual page 507

2. When using an external 24 V power supply, (e.g. SITOP), the 24 V terminal adapter must
be used. Miniature circuit-breakers are recommended as overcurrent protective device for
cables and busbars. The ground potential M must be connected to the protective conductor
system (DVC A).
Figure 9-2
When selecting the miniature circuit-breakers, you must take into account the following
standards:
EN 61800-5-1, EN 60204-1, IEC 60364-5-52, IEC 60287-1 to -3, EN 60228 and UL 508C.
The following conditions for the conductors/cables should be used as basis:
● Ambient temperature 55 °C
● Limit conductor temperature ≥ 75 °C for operation with the rated load current
● Cable length max.:
Further, the conductors/cables should be routed so that
● max. 1 conductor pair, bundled and
● the 24 V conductors should be separately routed away from other cables and conductors
Booksize power units
Manual, (GH2), 06/2008, 6SL3097-2AC00-0BP6
Example of 24 V DC fuse protection
– 10 m for the supply cables
– 30 m for signal lines
that could conduct the operating current.
Cabinet Design and EMC Booksize
9.3 24 V DC supply voltage
507