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Using an external 24 V power supply
SELV or PELV power supplies can be used for the external 24 V volt supply, e.g. SITOP. The ground
potential must be connected to the protective conductor system at the power supply output
(PELV). The cross-section of this connection must be at least as large as the cross-section of the
24 V conductors.
A 24 V terminal adapter must be connected to the component for the infeed. The external power
supply should be located very close to the load.
Figure 8-3
8.8.3
Overcurrent protection
The cables on the primary and secondary sides of the 24 V power supply 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. Note the following points:
• Load levels as a result of connected loads, including the rated diversity factor depending on
the operation of the machine
• Current-carrying capacity of the conductors used and cables in normal and short-circuit
conditions
• Ambient temperature
• Cable bundling (laying cables in a common duct)
• Type of cable routing
EN 60204-1, Section 14, can be used to determine the overcurrent protective devices.
Booksize power units
Equipment Manual, 01/2022, 6SL3097-6AC30-0BP0
Example of a 24 V supply via an external power supply
Control cabinet design and EMC booksize
8.8 24 V DC supply voltage
127
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