Eaton Electrical Cutler Hammer MN05001002E - Manual (Page 26)

Intelligent Technologies QCPort System Install Manual
November 2005
MN05001002E For more information visit www.eatonelectrical.com Page 26
Appendix A: Using Long Run Cables
When devices require locating further than 100 feet [30 meters] from one another, the
physical media changes from QCPort Interconnects to Long Run cables. This cable is
better rated for current carrying capacity and for the RS485 communication.
When connecting between Long Run and a QCPort device, the D77E-QPLR is required
to change the physical media. The D77E-QPLR provides for screw lugs for connection to
industrial RS485 cable.
Example of Long Run Cable: One Power Supply (End-Connected)
The following example uses the full calculation method to determine the configuration for
one end-connected power supply on a thick cable trunk line.
• Device 1 and Device 2 cause the same voltage drop, but Device 2 is twice as far
from the power supply and draws half as much current.
• Device 4 draws the least amount of current, but it is farthest from the power
supply and causes the greatest incremental voltage drop.
Figure 13 : Example of Long Run Cable: One Power Supply (End-Connected)
Device 1
1.0 A
Device 2
0.5 A
Device 3
0.4 A
Device 4
0.3 A
T
T
95 ft
18 ft
36 ft
43 ft
T – Biasing resistor
Power
Supply