ABB AC 800F

4 Cabling the AC 800F
4-59
The impedances reduce line
reflections normally occurring at
each connection point.
The series impedances are
matched with the line parameters
of the Profibus cable to be
connected.
Fig. 4-35 Profibus connector, internal circuitry
The bus cable to be used for the bus module is specified in DIN 19245/EN 50170 as
linetypeAandcanbeusedaccordingtothefollowingtable:
Parameters Line A
Characteristic impedance in Ω
135 ... 165
Capacitance per unit length (pF/m) <30
Loop resistance (Ω/km)
110
Wire diameter (mm) 0.64
Cross-sectional area of wire (mm
2
) >0.34
From the line parameters specified above result the following bus segment lengths:
Transmission rate in kBit/s 9.6 19.2 93.75 187.5 500 1500 12000
Range in m/segment 1200 1200 1200 1000 400 200 100
If you should wish to use a transmission rate which is not listed in the table above you
can approximately determine the permissible length through linear interpolation of two
adjacent transmission rates from the table.
Example
You are using a transmission rate of 3 Mbauds and would like to determine
approximately the max. line length l
3Mbauds
. The transmission rates in the table close
to this value are 1.5 Mbauds with l
1,5Mbauds
and 12 Mbauds with l
12Mbauds
. Thus,
you can calculate the line length l
3Mbauds
:
l
3Mbauds
l
1.5Mbauds
.
(),
3Mbauds 1.5Mbauds
l
1.5Mbauds
l
12Mbauds
1,5Mbauds 12Mbauds
l
3Mbauds
≈ 185 m