Spur Voltage Limited By The External Fieldbus Power Supply, Fisco Examination - Pepperl+Fuchs R2-SP-IC Series Manual

Segment Protector
Hazardous Area Installation and Use
Max. voltage
Uo
32 V, internal
limitation
32 V, internal
limitation
 24V, trunk
voltage
limitation
The requirements for typical fieldbus products for use in Zone 2 installations are summarized in
the manual: 'Using Pepperl+Fuchs fieldbus equipment in Zone 2 hazardous area environment'.
This document is supplied separately and can be obtained from Pepperl+Fuchs Internet
product data base.
3.2.3 Spur Voltage Limited by the External Fieldbus Power Supply, FISCO
Examination
When using intrinsically safe fieldbus power supplies to directly limit the spur output safety
voltage, it is necessary to choose a suitable fieldbus power supply for use with the Segment
Protector. The power supply used determines the type of Zone 2 or Division 2 installations and
the certified field devices that can be connected to the spurs of the Segment Protector in the
Zone 2 or Division 2 area.
A check must be performed to ensure that the correct type of power supply module is used for
the required safety output parameters. For example, the output voltage must be equal to or less
than the maximum voltage of the connected field devices.
In case a power supply with U
groups IIC, IIB, IIA at the spurs that are permitted, are:
U = 17.5 V, I
■
o
The safety evaluation follows the FISCO concept defined in EN60079-11.
The parameters of the cable used must be within the following ranges:
R' = 15...150 Ohm/km (loop resistance)
■
L' = 0.4...1 mH/km
■
C' = 45...200 nF/km (incl. a possibly existing shield)
■
C' = C'wire/wire + 0.5 * C'wire/shield (with floating field apparatus)
■
C' = C'wire/wire + C'wire/shield (if the shield is connected to one pole of the fieldbus
■
devices supply circuit)
From the safety point of view, the maximum length of the Segment Protector spur cable is
1000 m for IIC and 5000 m for IIB, as each spur output is specified as an independent FISCO
source.
Requirements for typical fieldbus products for use in Zone 2 installations are summarized in the
manual: 'Using Pepperl+Fuchs fieldbus equipment in Zone 2 hazardous area environment`.
This document is supplied separately and can be obtained from Pepperl+Fuchs Internet
product data base.
14
Short circuit
Gas groups current Io
IIC 46 mA
IIB/IIA 65 mA
IIC/IIB/IIA 65 mA
 17.5 V is used, the resulting safety output values for gas
o
= 65 mA, L = 0.25 mH, C
o o
Capacitance
Co Inductance Lo
60 nF 0.125 mH
60 nF 0.25 mH
60 nF 0.25 mH
= 60 nF (switch 1 in position 2)
o
Switch 1
position
Position 1
Position 2
Position 2