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Connecting
8.5 Power supply
8.5.2
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 8-3
Typ. current consumption
1.865 A
NCU only (processor, memory, etc.)
1)
NCU with full load at all outputs (digital outputs, USB, DRIVE-CLiQ, PROFIBUS DP, etc.)
2)
Requirements of DC power supplies
Electric shock as a result of an unsafe DC power supply
If an unsafe DC power supply is connected, exposed components may be at a hazardous
voltage level, which can result in serious injury or death.
• Use a PELV/DVC A category circuit according to EN 61010-1 as the DC power supply.
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 8-4
Rated voltage
Non-periodic overvoltages
66
Input voltage specification
1)
WARNING
WARNING
DC power supply requirements according to EN 61131-2
Voltage range (average value)
Voltage ripple peak-to-peak
Ramp-up time when switched on
Max. power consumption
14.89 A
24 V DC
20.4 VDC to 28.8 VDC
5% (unfiltered 6-pulse rectification)
Any
≤ 35 V
Equipment Manual, 01/2022, A5E45627807B AE
2)
NCU 1750
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