Cables and Lines
8
Cables and Lines
8.1
Calculation Tool for Cable Cross-Sections
If remote SiPass components are to be connected to the ACC, the following calculation tool might be
helpful.
Use a shielded weak-current cable type IY (St)Y for all bus lines. The cross-
sections of the leads have to be chosen by considering the following criteria:
power consumption of the connected system components/modules
Line length
Intermittently needed switching current (e.g. relay exits)
However, a min. diameter of 0.6 mm per lead is required.
The supply voltage in all system components/modules may not fall below 18 V DC.
With a min. permissible battery voltage of 21 V, this yields a max. voltage drop of
3V DC pertaining to the entire line length.
(
Caution: Total length = line to and back).
Resistance values for the conductor cross-section calculation:
Line length = 100 m
Wire Ø 0.6 mm (0.28 mm
2
)
⇒
6.5 Ohm
Wire Ø 0.8 mm (0.56 mm
2
)
⇒
3.6 Ohm
Calculation formulae
Voltage drop with applied current
A
I
L
U
⋅
⋅
=
χ
Conductor cross-section with applied current
and 0.5 V voltage drop along line:
L
= Line length of line leading to unit and
back
in
meters
I
= Current in ampere
χ
= spec. conduct. value for copper
2
56
mm
m
⋅
Ω
=
A
= Lead cross-section in mm
2
U
= Voltage in V
2
.......
5
.
0
56
mm
I
L
U
I
L
A
=
⋅
⋅
=
⋅
⋅
=
χ
17
Siemens Building Technologies
A24205-A335-B219.doc
Fire & Security Products
08.2004
