7.5.2 Requirements for the power supply
External 24 V power supply
Power is supplied to the NCU by an external 24 V power supply (e.g.: SITOP). The following
power consumption values for an NCU provide a configuration basis for calculating the 24 VDC
power supply.
Table 7-3 Input voltage specification
Typ. current consumption
1)
Max. power consumption
2)
1.865 A 14.89 A
1)
NCU only (processor, memory, etc.)
2)
NCU with full load at all outputs (digital outputs, USB, DRIVE-CLiQ, PROFIBUS DP, etc.)
Requirements of DC power supplies
WARNING
Electric shock when connected to an unsafe power supply
When equipment is connected to an unsafe power supply, exposed components may be at a
hazardous voltage level, which might result in serious injury or death.
The DC power supply must be implemented as Category PELV/DVC A circuit according to
EN 61010-1.
WARNING
Electric shock due to inadequately protected power supply cables
If power supply cables are inadequately protected, then lightning strikes can result in a surge
voltage. This can result in death, serious injury and material damage.
In the case of supply lines > 10 m, protectors must be installed at the device input in order to
protect against lightning (surge).
The DC power supply must be connected to the ground/shield of the NCU for EMC and/or
functional reasons. For EMC reasons, this connection should only be made at one point. This
connection is normally provided as standard in the S7-1500 I/Os. In exceptional
circumstances when this is not the case, the ground connection should be made on the
grounding rail of the control cabinet; please also refer to /EMC/EMC Installation Guide.
Table 7-4 DC power supply requirements according to EN 61131-2
Rated voltage 24 VDC
Voltage range (average value) 20.4 VDC to 28.8 VDC
Voltage ripple peak-to-peak 5% (unfiltered 6-pulse rectification)
Ramp-up time at POWER ON Any
Connecting
7.5 Power supply
NCU 1760
60 Equipment Manual, 02/2020, A5E45627861B AB
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