Overcurrent Protection - Siemens SINAMICS S120 Equipment Manual

Cabinet Design and EMC
14.3 24 V DC Supply Voltage
14.3.4

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
● Bundling of the cables in a one duct
● Cable laying method to EN 60204-1
EN 60204-1, Section 14, can be used to determine the overcurrent protection devices.
The recommended overcurrent protection devices on the primary side are circuit-breakers as
specified in Siemens catalog NSK. Miniature circuit-breakers are recommended as
overcurrent protection devices on the secondary side. The MCBs can be selected according
to Siemens catalog "BETA Modular Installation Devices - ET B1".
The 24 V DC supply for the following booksize components:
● Line Modules
● Motor Modules
● Braking Modules
● Capacitor Modules
● Control Supply Modules
is implemented in the components by means of a 24 V busbar for 24 V DC and reference
potential. The current carrying capacity of these bars is 20 A. The power supply is connected
via a 24 V terminal adapter. MCBs are recommended to protect the cables from overcurrent.
These overcurrent protection devices also protect the 24 V busbars. To protect against
ground faults, the ground potential must be connected to the protective conductor system.
314
conditions
Booksize cold-plate power units
Manual, (GH4), 03.2007, 6SL3097-2AJ00-0BP4