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DeviceNet Physical Layer and Media
Adept SmartController User’s Guide, Rev. E 123
The maximum current rating of a thick cable trunk line is 8A.Verify that this complies
with your national and international standards. It might be necessary to limit the
maximum current to a lower value if standards in the U.S. or Canada apply. The
maximum current value is a theoretical value. The cable size supports a higher current
than 8A. Depending on the topology of nodes relative to the power supply, higher
currents might be possible. See the DeviceNet technical specifications for further
information.
The maximum current rating of a thin cable trunk line is 3A. If you use the thin cable on a
long line, the resistance of the cable decreases the maximum current value. See Table B-5
and the DeviceNet technical specifications and for further information.
For the calculation of the maximum current at a specific length, use the following formula:
Where:
l= Length of the drop line in meters (m)
i= Maximum current in amps
This calculation applies to the sum of the currents of all the nodes on the selected drop
line. The length (l) is not the cumulative length of the drop line; it is the maximum
distance from any node on the dropline to the trunk line.
It is important to note that voltage differences between the V– and V+ conductors need to
be between 11V and 25V. The common-mode voltage between any two places on the V–
wire must not exceed 5V.
Table B-5. Maximum Current on a Dropline Relative to its Length
Length of Dropline Maximum Current
1.5 m (5 ft.) 3A
2.0 m (6.6 ft.) 2A
3.3 m (10 ft.) 1 1.5A
4.5m (15 ft.) 1A
6m (20 ft.) 0.75A
i
4.57
l
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