Siemens S5-155U System Manual page 324

Installation and Startup
ELR
Output 1
Figure 8-11 Parallel Connection of Outputs for AC Voltage Outputs
Connection of input/output
modules to two power supply
units
0 V
DI
DI
e.g. 420
e.g. 420
I I I I I
I I
AC
+
230 V
_
DC
24 V
Figure 8-12 Feeding of Non-Floating Input/Output Modules from Two Power Supply Units
8 - 26
The load can also be switched via a contact.
Manu-
ELR
al
Output 2
Load
Given here are two examples of the feeding of inputs and outputs of
different modules from two power supply units.
With non-floating input/output modules, the negative terminals (L-) of
the power supply units are connected to reference potential (PE)
because the inputs of the 420 module are referred to chassis ground.
0 V
L Q Q
I I +
2 L +
1 L +
_
L
Phase (L)
ELR = Electronic Load Relay
Neutral (N)
Reference Potential
0 V
0 V
DQ DQ
e.g. 441 e.g. 441
Q L Q Q L Q L Q Q
+ + +
AC
+
230 V
_
DC
24 V
C79000-B8576-C199-03
Central Ground Point
or Rack
of the CC/EU
and
Connection
to Protective
Conductor (PE)
System Manual