Juniper MX2020 Hardware Manual page 42

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.
NOTE: Depending on the voltage of the DC feeds, power can be drawn from both feeds.
The feed with higher voltage provides more power. If the difference between the voltages
is sufficient, then the higher voltage feed provides all the power. When the voltages are
exactly the same, equal power is drawn from both feeds.
DC PDMs (240 V China)—There are two PDMs per power subsystem capable of carrying nine feeds
each. You can install a total of four PDMs (240 V China) into a router. Each DC PSM is capable of
delivering 2500 W of power. 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 will
provide full power.
NOTE: Depending on the voltage of the DC feeds, power can be drawn from both feeds.
The feed with higher voltage provides more power. If the difference between the voltages
is sufficient, then the higher voltage feed provides all the power. When the voltages are
exactly the same, equal power is drawn from both feeds.
AC power subsystem—The AC power subsystem is feed redundant. Each PSM takes in two AC feeds
and uses one of the two. One AC feed is active at a time. If one feed fails, the PSM automatically switches
over to the other feed without disrupting system function. In the three-phase power systems, the AC
power going to the PSMs is split into three individual phases (wye) or a pair of phases (delta). Each PSM
works on a single phase; therefore, the power system works independent of the type of AC feed
connected. You can connect one or two AC 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.
AC PSM—The MX2020 AC PSMs are hot-removable and hot-insertable. The AC PSMs have a dual
redundant feed (INP0 and INP1). One input feed is active during operation. These feeds are set by the
input mode DIP switch located on the AC PSM (see MX2020 AC Power Supply Module Description). Each
AC PSM works with a single phase derived from either three-phase delta 200-240 VAC (line-to-line) or
three-phase wye 200-240 VAC (line-to-neutral). Each AC PSM is capable of delivering 2500 W of power.
AC PDM—Up to nine PSMs can be connected through the AC PDM. The MX2020 supports connection
of a single-phase or three-phase (delta or wye) AC PDM. The three-phase AC PDMs require two
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