VEGA VEGAPULS 51K…54K Profibus PA - Manual (Page 30)

30 VEGAPULS 51P … 54P
24890-EN-041227
Electrical connection
The boundary conditions for an Ex safe bus
configuration have been laid down in the so-
called Fieldbus Intrinsically Safe Concept
(FISCO). Therein the participants and the
bus cables with their electrical data have
been determined, so that the linking of these
components always meets Ex requirements.
A more time-consuming Ex calculation is
therefore 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
coupler.
Watch out for potential losses
Due to potential loss, grounding on both
sides without a potential equalisation system
is not allowed 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 (as well as the
enclosed safety data sheet) that come with
the Ex sensor.
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