ABB AC 800M User Manual page 24

FISCO (Fieldbus Intrinsically Safe Concept)
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On condition that the points are all satisfied, the proof of intrinsic safety has been
provided by means of the FISCO model. Devices that are certified in accordance
with FISCO are proven to be intrinsically safe and can be used in a plant's
hazardous areas without the need for additional calculation effort. If FISCO-
approved devices are used, more devices can be operate on a single line and it is
allowed to replace devices during runtime by devices of other manufacturer or to
expand the bus line with additional devices.
The prerequisite for being allowed to bear the proof of intrinsic safety in
accordance with the FISCO Model is, that the Linking Device and all fieldbus
stations are certified according to FISCO.
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– capacitance coating: 80 nF/km < C'< 200 nF/km (including the shield)
Taking the shield into consideration, the capacitance coating is calculated as
follows:
– C' = C'conductor/conductor + 0.5 * C'conductor/shield if the bus line is
potential free
or
– C' = C'conductor/conductor + C'conductor/shield if the shield is
connected with a pole of the Linking Device/Power Link.
The bus segment must be terminated on both ends of the line with a fieldbus
terminator. According to the FISCO model the terminal bus resistance must
conform to the following limits:
– 90 Ohm < R < 100 Ohm
– 0 µF < C < 2,2 µF
Section 1 Introduction
3BDS009029R5001 B