Isolated Or Non-Isolated Modules - Siemens SIMATIC S7-300 Hardware And Installation Manual

5.8.4 Isolated or non-isolated modules?

Isolated modules
In configurations with isolated modules, the reference potentials of the control
circuit (M
internal
Application
Use isolated modules for:
• All AC load circuits
• DC load circuits with separate reference potential
Examples:
DC load circuits whose sensors have different reference potentials (for
–
example if grounded sensors are located at some considerable distance
from the control system and no equipotential bonding is possible)
DC load circuits with grounded positive pole (L+) (battery circuits).
–
Isolated modules and grounding concept
You can use isolated modules, regardless of whether or not the control system's
reference potential is grounded.
S7-300 Programmable Controller Hardware and Installation
A5E00105492-02
) and load circuit (M
external
) are electrically isolated (see Figure).
Configuring
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