II - DCE FEL ČVUT v Praze

Minimum thread
measure
Mechanical Configuration of an Automation System with SIMATIC S7 Ex Modules
I/O Modules with Intrinsically-Safe Signals
C79000-G7076-C152-04
All system components which can supply electrical energy in any form
whatsoever must fulfill this condition. This includes in particular:
– The power supply module PS307. It fulfills this condition.
– The MPI interface. It fulfills this condition when all users operate with
safety extra-low voltage. SIMATIC automation systems and
programming units fulfill this condition.
– 115/230V modules. Even if they are used in another cell or in another
programmable controller they must feature safety extra-low voltage on
the system side (i.e. towards the backplane bus).
Any other power circuit (24V DC) used in the system must feature safety
functional extra-low voltage. Refer to the corresponding specifications or
consult the manufacturer.
Also bear in mind that sensors and actuators with external power supply may
be connected to I/O modules. Also ensure a safety extra-low voltage is used
in this case. Even in the event of a fault, the process signal of a 24V digital
module must never reach a fault voltage Um > 60V. This also applies to
non-intrinsically safe components.
Note
All voltage sources, e.g. 24V internal load voltage supplies, 24V external
load voltage supplies, 5V bus voltage, must be electrically interconnected
such that no voltage additions to the individual voltage sources can occur
even under conditions with differences in potential thus ensuring the fault
voltage Um cannot be exceeded You can achieve this, for example, by
referring all voltage sources in the system to the functional ground. Also
refer to the instructions provided in the relevant manuals (see Foreword) for
this purpose. The maximum possible fault voltage Um in the system is 60V.
A minimum thread measure of 50 mm must be maintained between
connection terminals with safety functional extra-low voltage and
intrinsically safe connections.In the process connector this is achieved by the
use of a line chamber (refer to Section 1.2).
It is possible that the specified thread measure cannot be maintained in
individual module components. In this case, you must use the spacer module
DM 370 (refer to Section 1.3) which you must set such that it does not take
up an address range. If you use the ET 200M Distributed I/O, you should
read Section 1.5.
Also take care with regard to the wiring to ensure this specified spacing is
maintained between intrinsically safe and non-intrinsically safe terminals.
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