VEGA VEGAPULS 45 Profibus PA - Manual (Page 32)

32 VEGAPULS 42, 44 and 45 – Profibus PA
24908-EN-041227
Electrical connection
In the so-called Fieldbus Intrinsically Safe
Concept (FISCO), the boundary 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, ensuring that the linking of
these components always meets the 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
couplers.
Watch out for potential losses
Due to potential losses, grounding on both
ends 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 sensors.
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