VEGA VEGAFLEX 55P (Profibus PA) - Manual (Page 20)

20 VEGAFLEX 55P (Profibus PA)
Electrical connection
In the so-called Fieldbus Intrinsically Safe
Concept (FISCO), the general conditions for
an Ex safe bus configuration have been laid
down. Therein, the participants and the bus
cables with their electrical data have been
determined, so that the linking of these com-
ponents always meets Ex requirements. A
more time-consuming Ex calculation is there-
fore not necessary. You can build your Ex
bus according to the IEC standard
1158-2.
The Ex segment coupler delivers a controlled
power supply to the PA bus. It acts as
source in the PA branch. All other compo-
nents (field instruments and bus terminators)
are only consumers. A field instrument must
consume at least 10 mA. Ideally, an individual
sensor should not consume more than
10 mA, so that the number of instruments can
be as large as possible.
VEGA PA sensors, whether Ex or non Ex,
consume a constant current of 10 mA. Ac-
cording to the Profibus specification, this is
the minimum participant current. With VEGA
sensors, it is therefore possible to connect 10
sensors (also in Ex environment) even with a
limited energy supply from the Ex segment
couplers.
Watch out for potential losses
Due to potential losses, earthing on both
ends without a potential equalisation system
is prohibited in Ex applications. If an instru-
ment is used in hazardous areas, the re-
quired regulations, conformity and type
approval certificates for systems in Ex areas
must be noted (e.g. DIN 0165). Please also
note the approval documents with the safety
data sheet attached to the Ex sensors.
Ex protection
If an instrument is used in dust-Ex areas, the
necessary regulations as well as the StEx
certificate of VEGAFLEX for systems in dust
Ex areas must be taken into account.
Electrical data of the cables
R
DC
No. of A in Z
31.25kHz
C in Damping Screen
cores mm 2 nF/km
SINEC 6XV1 44
Ω
/km 2 0.75 100
Ω
< 90 < 3 dB/km Cu braiding
830-5AH10 +/- 20
Ω
39 kHz
(Siemens)
SINEC L26XV1 44
Ω
/km 2 0.75 100
Ω
< 90 < 3 dB/km Cu braiding
830-35H10 +/- 20
Ω
39 kHz
(Siemens)
3079A 105
Ω
/km 2 0.32 150
Ω
29.5 < 3 dB/km Foil
(Belden) 39 kHz