Juniper MX2020 Hardware Manual page 35

Chapter 1: MX2020 Router Description
Power distribution modules (PDMs)—In the DC 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 kicks in to provide full power. A total of
four PDMs can be installed into a router. Each DC PDM operates with up to nine separate
feeds of either 60-amp or 80-amp current limit. The capacity of these feeds is relayed
to system software through a switch located on the DC PDM. The MX2020 router
supports two types of three–phase power system PDMs. The three–phase delta and
three–phase wye. Individual phases are taken from three-phase feeds to individual
PSMs. One AC feed provides power to six PSMs, while the second input feed provides
power to the remaining three PSMs (supporting a total of nine PSMs).
Power supply modules (PSMs)—All AC or DC PSMs in a subsystem share the load (the
nine PSMs on the top half share the load, as well as the nine PSMs on the bottom share
the load). If one PSM fails in a redundant configuration, the remaining PSMs provide
power to FRUs. In the AC or DC configuration, up to eighteen PSMs may be required to
supply power to a fully configured router. Nine PSMs in the lower card cage supply
power to the two CB-REs (active and redundant), eight SFBs, lower ten MPCs, two
lower fan trays and one fan tray on the top half. Nine PSMs in the upper card cage
supply power to the two upper fan trays, upper ten MPCs, two CB-REs (active and
redundant), eight SFBs, and a fan tray in the lower card cage. 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.
Cooling system—The cooling system has a total of four fan trays— two per zone—which
are controlled by the host subsystem. Each zone is made up of a set of ten MPCs, four
SFBs, and one CB-RE, (see "MX2020 Cooling System Description" on page 54). If one
of the fans fails, the host subsystem increases the speed of the remaining fans to
provide sufficient, cooling for the router. The fan trays are powered by two power
subsystems that are divided into zones (upper zone 1 and lower zone 0).
Related MX2020 Router Overview on page 3
Documentation
Displaying MX2020 Router Components and Serial Numbers on page 393
Guidelines for Packing Router Components for Shipment on page 413
Returning a Hardware Component to Juniper Networks, Inc. on page 410
Copyright © 2013, Juniper Networks, Inc. 9