Eaton Electrical MN05001002E Manual De Usuario

 

Intelligent Technologies QCPort System Install Manual 

November 2005  

 

MN05001002E 

For more information visit 

www.eatonelectrical.com

  

Page 

22

 

A power supply that is not end connected creates two sections of cable.  Because of this, 
each section needs to be evaluated separately.  The equation sums the calculated drop 
for each device and compares it to 4.65V. 

 

L

n

L = The distance (ft) between the 
device and the power supply, 
excluding the drop line distance. 
n = The number of the device 
being evaluated, starting with 1 for 
the device closest to the power 
supply and increasing by 1 for the 
next device. 

 (0.005) 

The nominal-contact resistance used for 
every connection to the trunk line. 

Rc 

Long Run 

0.021 (ohm/ft) 

QCPort Interconnect 

0.105 (ohm/ft) 

 4.65V 

The maximum voltage drop allowed.  
This is the total cable system voltage 
drop of 5.00V minus 0.35V reserved for 
drop line voltage drop. 

N

t

The number of taps between the 
device being evaluated and the 
power supply.  For example:  

•  When a device is the first 

one closest to the power 
supply, this number is 1. 

•  When a node has one device 

between it and the power 
supply, this number is 2. 

•  When 10 devices exist 

between the evaluated node 
and the power supply, this 
number is 11. 

For a device attached as a drop 
from a device, the currents for the 
trunk and drop device should be 
summed and used with the 
equation only once. 

 

I

n

I = The current drawn from the cable 
system by the device.  For currents 
within 90% of the maximum, use the 
nominal device current.  Otherwise, use 
the maximum rated current of the device. 

For a device attached as a drop from a 
device, the currents for the trunk and 
drop device should be summed and 
counted as one tap. 

n = The number of devices being 
evaluated, starting with 1 for the device 
closest to the power supply and 
increasing by 1 for the next device.