Siemens Automation System S7-400 - Manual (Page 62)

Wiring the S7-400
4-2
Automation System S7-400 Hardware and Installation
A5E00850741-01
4.1 Supplying Power to Modules
Power Supply Modules and Load Current Power Supplies
The modules of the S7-400 system are supplied with all the required operating
voltages by a power supply module, via the backplane bus of the rack. Which
power supply module you use in a rack depends on your system requirements (line
voltage, current consumption of the modules used).
You must provide load voltages and currents via external load current power
supplies.
The following figure shows how the individual modules of the S7-400 are supplied
with current and voltage.
S7-400
power supply
module
S7-400
modules (DC
or AC)
Operating voltages
5 VDC and 24 VDC
via backplane bus
Load current via
front connector
Load current power
supply
Line voltage:
120/230 VAC
with supply
isolator
or 24 VDC
Note
The power supply modules must not be connected in parallel on their secondary
sides.