User Manual
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Siemens TX-I/O Engineering and installation guide CM110562en_13
Building Technologies Principles of electrical design 2019-05-15
Solutions for sub-islands without power supply modules
In these examples earthing is not admetted because conductor ⊥ carries supply
currents. Case 2 B.
First, for comparison purposes, example A without island bus expansion.
The following lengths and power are permitted per page 81:
< Lmax
< 0.6A
A
10562z156
Cable island bus (wire CS, CD and ⊥)
Length Lmax
Max. power for remote I/O row
Round cable 2.5 mm2 / AWG14
50 m
0.6 A
Coaxial cable parallel with 2.5 mm2
100 m
0.6 A
Example T illustrates how the distance can be increased by resolving communication
of the decentralized I/O row with the island bus expansion, power (wire CS and ⊥ only)
can, however, originate from the local sub-island.
This solution is of interest when the decentralized I/O row has only a few I/O modules
with little power consumption (e.g. digital or analog inputs, see page 100), and you do
not want to install a power supply module.
< L
T
10562z157
CS,
T
Cable island bus (wire CS and ⊥ only)
Length L
Max. power for decentralized I/O row
Round cable 2.5 mm2 / AWG14
200 m
150 mA (of which 50 mA for TX1A.IBE)
Round cable 2.5 mm2 / AWG14
100 m
300 mA (of which 50 mA for TX1A.IBE)
Round cable 2.5 mm2 / AWG14
50 m
600 mA (of which 50 mA for TX1A.IBE)
Example U illustrates decentralized mini I/O rows analogous to example C and
distributed over a maximum length of 100 m.
The long distance reduces permissible power to 150 mA, in other words, one I/O
module can be operated.
< 1/3 L
< 0.075A
< 2/3 L
< L
U
10562z158
CS,
T
< 0.075A < 0.075A
Cable island bus (wire CS and ⊥ only)
Length L
Max. power for each decentralized I/O row
Rounds cable 2.5 mm2 / AWG14
100 m
150 mA (of which 50 mA for TX1A.IBE)
Distances and power in the power cables (wire CS and ⊥) are based on the specifi-
cation that a maximum voltage drop of 0.5 V is allowed on both CS and ⊥.
The reasons, however, in examples T and U is not the stability of island bus commu-
nication, but rather the power supply for decentralized I/O modules: When the power
supply module / P-Bus-BIM provides only the minimum specified voltage of 22.5 V,
then only 21.5 V remains at the end of the wire for the last I/O module.
STOP
Note!
Note