Juniper MX2020 Hardware Manual page 127

fan trays (0, 1, 2, and 3; 0 and 1 for MX2008)
MPCs in slot 0 through 9
CB-REs in slot 0 and 1
SFBs in slot 0 through 7
The MX2000 line of routers supports a three-phase delta AC power system, three-phase wye AC power
system, or a single-phase AC power system.
CAUTION:
The MX2000 line of routers configured for three-phase wye AC input power must use
only three-phase wye AC PDMs and three-phase AC PSMs. The systems configured
for three-phase delta AC input power must use only three-phase delta AC PDMs and
AC PSMs. The systems configured for single-phase AC input power must use only
single phase AC PDMS and AC PSMs.
In a three-phase AC power system, the AC power going to the PSMs is split into a pair of phases. Each
PSM works on a single phase. This means the power system works independent of the kind of AC feed
connected. You can connect one or two feeds, depending on the power system configuration, number of
PSMs, redundancy, and so on. Each phase from each of the two feeds is distributed among one or two
PSMs. One feed has each phase going to two PSMs and the other feed has each phase going to a single
PSM.
The single-phase AC power distribution module (PDM) provides an AC input power interface to the PSM
through the system power midplane. Up to nine PSMs can be connected to a single-phase AC PDM. Each
single-phase AC PDM accepts seven or nine AC power cords from a single-phase AC source. Each AC
input is independent and feeds one PSM.
The AC PSMs are hot-removable and hot-insertable.
Up to nine PSMs may be connected in parallel per power subsystem to increase available power for MPCs,
as needed and to provide redundancy.
Do not mix AC and DC PSMs or different PDM types within a single system.
Figure 44 on page 105 shows the AC PSM.
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