Siemens SIMATIC S5-115U User Manual page 105

S5-115U Manual
Operating a Programmable Controller with Field Devices on Non-grounded Supply
Neither the outer conductor nor the neutral are connected to the protective conductor in the case
of nongrounded supplies. Operation of the PLC with nonfloating power supply modules is not
permissible.
Please note the following when connecting power supply modules:
In networks with 3 x 230 V, you can connect the power supply module direct to two outer
conductors (see Figure 3.32).
In networks with 3 x 400 V, connection between the outer conductor and the neutral conductor is
not permissible (unacceptably high voltage in the case of ground fault). Use intermediate
transformers in these networks.
Low voltage distribution
e.g. IT system
L1
L2
L3
PE
Control power supply
AC
DC
Operating
ground
AC
AC
AC
DC
AC
DC
Figure 3-32. Operating a Programmable Controller with Field Devices on Nongrounded Supply
EWA 4NEB 811 6130-02b
Cabinet
L+
L+/L1
L-
U int
L-/N
L1
PS
M int
N PE
Protective conductor bar
in cabinet
24 to 230 V AC load power supply unit for
AC modules
5 to 60 V DC load power supply unit for
nonfloating DC modules
5 to 60 V DC load power supply unit for
floating DC modules
Installation Guidelines
Programmable controller
µ
P
Floating
Non- Non-
CPU
input
floating floating
input output
Field devices
Floating
output
3-39