GFK-2958E RSTi-EP User Manual 332
7.2 Potential Ratios
7.2.1 Basic aspects
As regards the potential ratios of a RSTi-EPsystem, the following aspects must be kept in mind:
• The power supply of the network adapter and I/O modules as well as field power is provided
via the power supply at the power-feed module (PF)
• A potential-free design is made possible through the use of an isolated power supply at the
system power supply and the field power supply
The block diagram shows the typical design of a RSTi-EP system. The power supply concept here
makes sure that, starting with a certain capacity utilisation, power refresh is implemented using
power-feed modules.
RSTi-EP Power Supply Concept
7.2.2 Potential-free Design
In a potential-free design, the reference potentials of control and load circuits are galvanically
isolated from each other. A potential-free design is necessary for the following:
–– Use of the power-feed module (EP-19xx), i.e. in all AC load circuits
–– DC load circuits that cannot be coupled
Potential-free installation depends on the type of earthing.
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