PairGain 150-1111-75, Руководство пользователя

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150-231-175-01, Revision 01 Appendix C - Functional Operation
HLU-231 List 7E September 23, 1998 51
Power Consumption: With Doublers
The maximum current drain is the current drawn from the shelf power supply when it is at minimum voltage (-42.5
VDC) under a worst case application. The worst case application for the HLU-231 List 7E occurs on a loop with
one HDU doubler, four 9000 ft, #26 AWG spans, and an HRU-412 that is providing 60 mA of CPE current. Under
these conditions the HLU-231 List 7E current drain from the -42.5 VDC battery is 0.80 A for the HDU-451 List
1 and 2, and 0.58 A for the HDU-451 List 3, 4, and M/M doublers. This CO current and other related power
parameters for this doubler application are listed in
Table 16 . The worst case loop conditions assumed for the 3
span line powering applications listed in Table 16 and Table 17 are a 2000 ohm total loop consisting of 9000 ft,
#26 AWG for span 1 and 2, and 6000 ft, #26 AWG for span 3.
The maximum shelf current drain allowed is a function of the shelf -48 VDC fuse. Table 17 lists the doubler shelf
deployment guidelines, as a function of the shelf fuse, for the more popular Type 220 configuration shelves. These
guidelines limit the maximum fuse load to 85% of shelf rated capacity. Use
Table 17 when selecting the
appropriate load fuses for the Building Distribution Fuse Bus (BDFB) when deploying the HiGain system
equipment in COs.
The maximum HLU-231 List 7E power dissipation is the power that is converted into heat within the unit. It
contributes to the total heat generated and is used to determine the maximum number of shelves per bay that do
not exceed the maximum power dissipation density in Watts/sq. ft.
In CO locations, the maximum power dissipation for open faced, natural convection cooled mountings is 134.7
Watts/sq. ft. as stated in NEBS standard TR-NWT-000063 section 4.2.3. The footprint of a 13 slot 23” SXSS shelf
is 7.024 sq. ft. Thus the maximum allowable dissipation is 946 W. This limits the number of HLU-231 List 7E
units per bay to 111 when powering the List 1 or List 2 doubler with CPE current OFF or when powering the
List 3, List 4, or M/M doubler with CPE current ON.
Note that this is a worst case situation since it assumes the entire CO is subjected to the maximum power density.
More favorable conditions would permit increasing the number of shelves per bay without jeopardizing the CO
thermal integrity.
M/M refers to the HDU-432 and HDU-439 mini doublers and the HDU-404, HDU-407, and HDU-409
micro doublers.
The power consumption and dissipation of a two doubler circuit with a locally powered remote
are the same as for a single doubler circuit with CPE current OFF, as listed in
Table 16 . The
power consumption and dissipation of a line powered, three span, 2000 ohm loop are the same
as for a single HDU-451 List 1 or 2 doubler circuit with CPE ON.