Overcurrent Protection - Siemens SINAMICS S120 Manual

9.3.4

Overcurrent protection

Cables on both the primary and the secondary side of the power supply unit must be
protected from overcurrent. Primary side protection must be implemented according to the
manufacturer's instructions. Secondary side protection must be rated to deal with the actual
conditions. In particular:
● Loading due to loads, possibly the simultaneity factor in response to machine operation
● Current carrying capacity of the conductors used and cables in normal and short-circuit
● Ambient temperature
● Cable bundling (e.g. laying in a common duct)
● Cable laying method to EN 60204-1
EN 60204-1, Section 14, can be used to determine the overcurrent protection devices.
Circuit-breakers from the Siemens NSK catalog are recommended as overcurrent protection
devices on the primary side, and miniature circuit-breakers or SITOP select 6EP1961-2BA00
as overcurrent protection devices on the secondary side. The MCBs can be selected
according to Siemens catalog "BETA Modular Installation Devices - ET B1".
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).
When selecting the circuit-breaker, the following standards must be carefully observed:
EN 61800-5-1, EN 60204-1, IEC 60364-5-52, IEC 60287-1 to -3, EN 60228 and UL 508C.
In so doing, the following conditions for the conductors/cables must be carefully taken into
consideration:
● Ambient temperature 55 °C
● Limiting conductor temperature ≥ 75 °C for operation with the rated load current
● Cable length max.:
In addition, the conductors/cables should be routed so that
● Max. 1 conductor pair is bundled, and
● The 24 V conductors/cables must be routed separately from other cables and conductors
AC Drive
Manual, (GH6), 07/2007 Edition, 6SL3097-2AL00-0BP2
conditions
– 10 m for the supply supply cables
– 30 m for signal lines
that can conduct operating currents.
Cabinet Design and EMC for Components, Blocksize Format
9.3 24 V DC supply voltage
297