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Guidelines for Electrical Installation
D301087 1211 - BL20 CANopen 7-4
7.2 Potential Relationships
7.2.1 General
The potential relationship of a CANopen system realized with BL20 modules is characterized by the
following:
„
The system’s power supply to the gateway, I/O modules and the field level is distributed via a Bus
Refreshing module.
„
All BL20 modules (gateway, Bus Refreshing, Power Feeding and I/O modules), are connected
capacitively via base modules to the mounting rails.
„
Separate power supplies for the system and the field level allow a potential-free installation.
The block diagram shows the arrangement of a typical BL20 station.
7.2.2 Potential-Free Installation
In a potential-free installation, the reference potentials of control and load circuitry are galvanically
isolated from each other.
A potential-free installation is necessary with
„
All AC load circuits (for example, when using the Power Feeding module BL20-PF-120/230VAC-D)
„
Floating DC load circuits
The potential-free installation does not depend on the method of grounding.
7.2.3 Non-isolated Installation
In a non-isolated installation, the reference potentials of the control and load circuitry are galvanically
connected.
Figure 7-2:
Block diagram of
a BL20 station
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Gateway Power Feeding Bus Refreshing I/O module I/O module I/O module Bus Refreshing
Logic Logic
5 V
Logic
24 V
2 O 2 O 4 I
24 V 24 V Field-
bus 24 V 230 V
Logic
DC DC
DC DC
+V -V