Rockwell Automation DeviceNet Media Design Installation Guide - Manual (Page 25)

Publication DNET-UM072C-EN-P - July 2004
Get Started 1-15
Guidelines for supplying power
The cable system requires the power supply to have a rise time of less than 250
milliseconds to within 5% of its rated output voltage. You should verify the
following:
• the power supply has its own current limit protection
• fuse protection is provided for each segment of the cable system
– any section leading away from a power supply must have protection
• the power supply is sized correctly to provide each device with its
required power
• derate the supply for temperature using the manufacturer’s guidelines
Choose a power supply
The total of all of the following factors must not exceed 3.25% of the nominal
24V needed for a DeviceNet cable system.
• initial power supply setting - 1.00%
• line regulation - 0.30%
• temperature drift - 0.60% (total)
• time drift - 1.05%
• load regulation - 0.30%
IMPORTANT
For thick cable and Class 2 flat cable, your national and
local codes may not permit the full use of the power system
capacity. For example, in the United States and Canada, the
power supplies that you use with Class 2 thick cable must
be Class 2 listed per the NEC and CECode. The total
current allowable in any section of thick cable must not
exceed 4A.
Class 1 power supplies allow for an 8A system, and the use
of Class 1 flat cable. See Appendix A for more information
about national and local codes. Appendix B, “Power
Output Devices”, provides important information to the
installer.
power
supply
Supply Power 3
Use the power supply to power the DeviceNet
cable system only. If a device requires a
separate 24V power source other than the
DeviceNet power source, you should use an
additional 24V power source.
DN
PS
Trunk drop
node power
node