Juniper MX2020 Hardware Manual page 115

CAUTION:
The systems configured for DC (-48 V) input power must use DC (-48 V) PDMS and
PSMs. The systems configured for DC (240 V China) input power must use DC (240
V China) PDMs and PSMs. The MX2010 systems configured for three-phase wye AC
input power must use only three-phase wye AC PDMs and AC PSMs. The systems
configured for three-phase delta AC input power must use three-phase delta AC PDMs
and AC PSMs. The systems configured for single-phase AC input power must use single
phase AC PDMS and AC PSMs.
Table 24: MX2020 DC Power Components
Component
DC power subsystem
DC Power Distribution Modules (-48 V)
Do not mix AC and DC PSMs or different PDM types within a single system.
Description
The MX2020 DC power system comprises two subsystems. Each power
subsystem provides power to 10 line-card slots, three fan trays, two
CB-REs, and eight SFBs. There are nine DC PSMs and two DC PDMs in
each subsystem. This means, if one power subsystem stops functioning
for any reason, only the MPCs will stop functioning; the router will
continue to function.
There are two types of DC power subsystems available for the MX2020:
a "base" DC power subsystem (MX2020-BASE-DC) and an "optimized"
or premium DC power subsystem (MX2020-PREMIUM2-DC).
See"Determining DC Power Requirements for Your MX2020 Router" on
page 209 for more information.
In the DC PDM (-48 V) configuration, each subsystem provides N+1 PSM
redundancy along with N+N feed redundancy. The power feeds from
different sources need to be connected to different PDMs. If feeds that
connect to one PDM fail in a redundant configuration, the other feed will
provide full power. You can install a total of four PDMs into a router.
Each DC PDM operates with seven feeds or nine feeds of either a 60-A
or 80-A current limit. You can select the input feed capacity (60-A or
80-A) by setting the DIP switch on the PDM to the rated amperage of
the DC power input feeds. Each DC PDM has seven or nine DC inputs
(–48 VDC) and return terminals for each input).
NOTE: The selected input capacity applies to all inputs of this PDM.
Selecting 60-A reduces the available power output capacity of the PSMs
supplied by this PDM.
In a redundant configuration, the 7-feed DC PDMs support a total of
fourteen 60-A or 80-A feeds, and the 9-feed DC PDMs support a total
of eighteen 60-A or 80-A feeds.
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