User's Manual

14 68P80801E35-A 9/1/2001
Parts and Suppliers EBTS System Manual - Vol 2
Determining Power Connection Wire Size
The cable loop length refers to the total length of wire within a given circuit. For
example, the combined length of the -48 Vdc (hot) lead and the DC return lead
equals the cable loop length. This would mean that a cabinet which needs 16 feet
of wire between the Power Supply rack and equipment cabinets has a total loop
length of 32 feet.
The wire size for the connection between the Power Supply rack and the
equipment cabinets is determined by the required wire length and the maximum
allowable voltage drop. The voltage drop in the loop must be kept to below
500 mV. The wire selected should be UL approved and contain a high number of
strands for flexibility. Table 11 shows the recommended wire sizes for various
loop lengths of the RF Cabinet. Table shows the recommended wire sizes for loop
lengths of the Control Cabinet
For a standard configuration, the equipment cabinets are located adjacent to the
Power Supply rack with a cable loop length less than 35’.
Each equipment cabinet has a total of four Power Supply Rack connections; two
-48 Vdc (hot) and two DC return. Each equipment cabinet contains two separate
power distribution systems. A single hot wire and a single return wire are used
for each side of the bus. Two return leads provide redundancy and allow a
uniform wire size to be used for all 48 Vdc power distribution system
connections.
Table 11 Power Connection Wire Size
Loop Length Wire Size
25 feet or less #6 AWG
25 to 40 feet #4 AWG
40 to 60 feet #2 AWG
60 to 130 feet 1/0 AWG
NOTE: The wire sizes listed are large enough to allow full RF
Cabinet Base Radio capacity.
Table 12 Power Connection Wire Size for Control Cabinet
Loop Length Wire Size
150 feet or less #6 AWG