Configuration Variants of the S7-400
6-15
Automation System S7-400 Configuration and Use
A5E0044271 1-02
6.8 Grounded / Ungrounded S7-400 Configurations
Introduction
Depending on the requirements in the plant, you can build the S7-400 with either
grounded or ungrounded reference potential.
Application
You should usually select a grounded configuration. A grounded configuration
guarantees a high degree of interference immunity. Any interference current that
occurs is discharged to building ground. In large, extensive plants, however, you
may be required to build the S7-400 ungrounded.
Connection Scheme
A removable bridge on the rack forms a galvanic connection to the building ground.
If this bridge is removed, the rack is connected to the building ground via an RC
network and therefore configured ungrounded. RF interference is discharged
through this RC network and static charges are prevented. Figure 6-7 shows the
rack and the removable bridge.
Galvanic connection
Connection to mounting rail
Connection to building ground
RC network
M
6.8nF 10MΩ
Removable
bridge
Reference potential M
Figure 6-7 S7-400 assembly with the removable bridge
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