Overcurrent Protection - Siemens S120 Manual

Note
A regulated DC power supply is required to operate motors with a built-in holding brake. The
power is supplied via the 24 V connection (Safe Brake Relay). The voltage tolerances of the
motor holding brakes (24 V ±10%) and the voltage drops of the connecting cables must be
taken into account.
The DC power supply should be set to 26 V. This ensures that the supply voltage for the
brake remains within the permissible range when the following conditions are fulfilled:
• Use of Siemens three-phase motors
• Use of Siemens MOTION-CONNECT power cables
• Motor cable lengths: max. 100 m
10.5.2

Overcurrent protection

The cables on the primary and secondary sides of the 24 V power supply unit must be
protected against overcurrent.
Primary side protection must be implemented according to the manufacturer's instructions.
Secondary side protection depends on the prevailing situation. Please note the following:
● Loading due to loads, including simultaneity factor depending on machine operation
● Current carrying capacity of the conductors used and cables in normal and short-circuit
● Ambient temperature
● Cable bundling (routing cables in a common duct)
● Cable routing method according to EN 60204-1
The overcurrent protection devices can be determined according to EN 60204-1, Section 14.
Circuit-breakers from Siemens Catalogs LV 1 and LV 1T are recommended as overcurrent
protection devices on the primary side.
Miniature circuit-breakers or SITOP select, 6EP1961-2BA00 are recommended as
overcurrent protection devices on the secondary side. The miniature circuit-breakers can
also be selected from Siemens LV 1 and LV 1T Catalogs.
Miniature circuit-breakers are recommended as overcurrent protection devices for the cables
and busbars. The ground potential M must be connected to the protective conductor system
(PELV / SELV).
When selecting the miniature circuit-breaker, local installation regulations must be carefully
complied with.
AC Drive
Manual, (GH6), 04/2014, 6SL3097-4AL00-0BP4
conditions
Cabinet design and EMC for components, Blocksize format
10.5 24 V DC Supply Voltage
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