Juniper MX2020 Hardware Manual page 40

DC power subsystem—The MX2020 DC power system is comprised of two subsystems. Each DC 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 power subsystem. This means, if one power subsystem stops
functioning for any reason, only the MPCs will stop functioning; the router will continue to function.
Figure 5 on page 14 illustrates feed redundancy for the MX2020 DC power subsystem.
Figure 5: MX2020 Router DC Power Subsystem Feed Redundancy
PDM 1
(feed B)
PSM PSM
0 1
PDM 0
(feed A)
Each DC power subsystem has two power zones: zone 0 and zone 1. A portion of power from each zone
is reserved to power critical FRUs. These FRUs allow the system to operate even if power to a complete
zone fails. Some FRUs draw power only from zone 0, some FRUs draw power only from zone 1, and
some FRUs draw power from both zone 0 and zone 1.
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).
The fan trays in an optimized DC power subsystem draw power from the power zones differently than
the fan trays in a base DC power subsystem. In a base DC power subsystem, two of the four fan trays
draw power from both zones. In the optimized DC power subsystem, two of the fan trays draw power
from only one zone. Because of this, the optimized power subsystem requires less power. See
"Determining DC Power Requirements for Your MX2020 Router" on page 209
about MX 2020 power distribution.
Figure 6 on page 15 illustrates how the power zones in the MX2020 base DC power subsystem distribute
power to FRUs
PSM
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for more information
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