Siemens installation manual Assembling an S7-400 with Isolated Modules, Definition

Wiring the S7-400

4.7Assembling an S7-400 with Isolated Modules

Definition

In a configuration with isolated modules, the reference potentials of the control circuit (Minternal) and the load circuit (Mexternal) are isolated (see also Figure 4-4).

Application

Isolated modules are used for:

•All AC load circuits

•DC load circuits with a separate reference potential Examples of load circuits with a separate reference potential:

--DC load circuits whose sensors have different reference potentials (for example, when grounded sensors are used far from the programmable controller and equipotential bonding is not possible).

--DC load circuits whose positive terminal (L+) is grounded (battery circuits).

Isolated Modules and Grounding Concept

You can use isolated modules, regardless of whether or not the reference potential of the programmable controller is grounded.

4-10	Automation System S7-400	Hardware and Installation
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