Siemens SIMATIC S5-95F Manual page 123

Expansion of Basic System with External I/Os
Configuration with Non-Grounded Reference Potential
In large systems, the various process areas often have different earth potentials. If you supply all
circuits with an electrically isolated functional extra-low voltage, you can operate an isolated S5-95F
configuration - even with non-isolated input and output modules.
In the isolated configuration, interference currents that occur are discharged by the standard
mounting rail via an RC network to the protective conductor. Grounding of the load voltages in an
isolated configuration is also only permissible via an RC network.
For the isolated configuration, you require electrically isolated power supply units. The sensors and
actuators must also fulfill the electrical isolation requirements.
Figure 5-25 shows the isolated configuration of an S5-95F programmable controller with capacitive
connection to the protective conductor bar.
Isolated
configuration
Battery
of standard
mounting
rail
I
O
Protective conductor bar
To configure the S5-95F with a non-grounded reference potential, you should proceed as
follows:
Mount the standard mounting rails in an isolated configuration
Connect the
Connect both subunits with each other
Connect the standard mounting rail with the protective conductor via an RC network
(rating of the RC network: R = 100 k , C = 1 µF/500 V)
Attention
!
If you operate the S5-95F with a non-grounded reference potential, the configuration
must be provided with an insulation monitor to detect double earth faults.
5-28
Subunit A
OUT DIGITAL
IN
A B
L+
L+
32
32
.0 .4
.0
.1 .5
.1
.2 .6
.2
.3 .7
.3
.4 .0
.4
.5 .1
.5
.6 .2
.6
.7 .3
.7
M
L+
33
33 34
.0
.0 .0
.1
.1 .1
.2
.2 .2
.3
.3 .3
.4
.5
.6
L+
.7
DC 24V
M
M
terminal of subunit A and subunit B with the standard mounting rail
Figure 5-25. Non-Grounded S5-95F Configuration
Battery
B A
I
O
S5-95F
Subunit B
IN
A B
L+
L+
32
32
.0 .4
.0
.1 .5
.1
.2 .6
.2
.3 .7
.3
.4 .0
.4
.5 .1
.5
.6 .2
.6
B
.7 .3
.7
M
L+
33
33 34
.0
.0 .0
.1
.1 .1
.2
.2 .2
.3
.3 .3
.4
.5
.6
L+
.7
DC 24V
M
M
EWA 4NEB 812 6210-02
A