Siemens S5-135U/155U - Manual (Page 51)

3-25
System Manual
C79000-G8576-C199-06
In cases in which the higher-level power supply is not grounded, you must
connect the programmable controller to a separate protective
conductor/ground (e.g. foundation ground). Operation of the PLC with
non-floating power supplies is not allowed.
When connecting the power supplies, please note:
In 3 x 230 V systems, you may connect the power supply directly to two
phases.
Schrank
Control Power Supply
L+
L–
L1
L2
PE
L+/L1
L–/L2
PE
AC
DC
AC
AC
AC
DC
AC
DC
Non-Float-
ing Input
L1
L2
L3
PE
e.g. IT System (3 X 230V)
Programmable Controller
Protective Conductor Bar
in Cabinet
Low-Voltage Distribution,
24 to 230 V AC Load Supply
for AC Modules
5 to 60 V DC Load Supply
for Non-Floating DC Modules
Process I/Os
Protective
Conductor
Grounding
PS
CPU U
0 V
int
А
Б
Б
Б
В
В
Г
Г
Д
Е
Non-Float-
ing Output Floating
Input Floating
Output
5 to 60 V DC Load Supply
for Floating DC Modules
Figure 3-10 Operating a Programmable Controller with Process I/Os from an Ungrounded Supply
In 3 x 400 V systems, a connection between phase and neutral conductor is
not allowed (excessively high voltage in the event of a ground fault).
Intermediate transformers should be used in these systems.
Operating a
Programmable
Controller with
Process I/Os from
an Ungrounded
Supply
Installation Guidelines