Siemens SIMATIC S5-115U, User Manual

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Installation Guidelines S5-115U Manual
3.4.3 Connecting Nonfloating and Floating Modules
The following sections show the special features involved in installations with nonfloating and
floating modules.
Installation with nonfloating modules
In installations with nonfloating modules, the reference potential of the control circuit (M
internal
)
and the load circuits (M
external
) are galvanically isolated.
The reference potential of the control circuit (M
internal
) is at the PE terminal or and must be
connected to the reference potential of the load circuit via a line to be run externally.
Figure 3.33 shows a simplified representation of an installation with nonfloating modules. The
installation is independent of the grounding concept. The connections for the grounding
measures are therefore
not shown:
Figure 3-33. Simplified Representation of an Installation with Nonfloating Modules
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PE
Control power
supply
24 V DC load power
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External connection for
uniform reference potential
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Voltage drop on line must not exceed 1 V, otherwise the reference potentials will shift and
result in module failures.
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EWA 4NEB 811 6130-02b