Commissioning Hardware PolyGard
®
DGC- 05
Page 6
PolyGard
is
a
registered
trademark
of
MSR
GAINBDGC05_E_1206
Phone.:
0049(0)8531/9004-0
Fax:
0049(0)8531/9004-54
Specification subject to change without notice.
MSR-Electronic GmbH, Würdinger Str. 27, D 94060 Pocking
www.msr-electronic.de
Made in Germany
3.3
Physical load capacity of the bus cable
The DT-05 transmitters work with a nominal operating voltage of 24 VDC. This tension is impressed via the shared
4-wire Twisted Pair Cable (JY(St)Y 2x2x0,8LG) with a cross-section of 0,5 mm
2
.
Therefore you have to calculate which cable length is allowable in dependence of the total power of the connected
DT- 05 / AT transmitters, in order to obtain the required minimum terminal voltage of 15 VDC at all of the DT- 05 /
AT transmitters.
Note:
The operating voltage supply of the EP- 05 modules mounted in the field always shall be executed via a separate
line, because due to the higher power requirement of the modules the allowable voltage drop in the bus cable only
permits relatively short cable lengths.
3.4
Calculation of the cable length
As described above, the field bus cable is only laid in line topology. There are three possibilities for a voltage drop
in the bus cable:
a. No return line of the cable
b. Return line of the cable
c. Parallel laying of the cable with a higher cross-section.
For calculating the permissible cable length an Excel program is available.
For fast projection some examples related to practice are calculated for the three possibilities concerning
maximum lengths of feed line cables and intermediate cables.
Laying of the cables without return line
Fig. 4 Cable without return line
DT- 05
(pieces)
AT- 34
(pieces)
Feed line
L feed (m)
Return line
(m)
Delta MP-MP
L2; L3... (m)
Total length
(m)
30 0 50 0 25
850
28 0 100 0 25 900
27 0 150 0 25
950*
14 14 50 0 25 400
12 12 100 0 25 400
10 10 150 150 25 350
*Cable length of max. 900 m exceeded!
DT
05
DT
05
DT
05
DT
05
DT
05
DGC-05
central control
2
30 V
L feed
L 2
L 3
L 4
L 5
+24
V
JY(St)Y 2x2x0.8LG
