schroff 11990-704, Руководство пользователя

Страница: 24 / 38

11990-704/705/706/707 (2-Slot ATCA Shelf)
Power 20 R1.2, March 2018
8.2 DC PEM
Two pluggable redundant DC Power Entry Modules (PEM) are located at the rear top side of
the Shelf. Each PEM provides power terminals for 35A power feed. Each power feed consists
of a –48 VDC cable and its corresponding return cable. The feed is protected by a 35 A fused
switch.
The power filtering consists of filtered power terminals and a discrete line-filter for each
power branch.The input voltage range for the Shelf is from -40VDC to -72VDC.In each power
feed, voltage measurement is implemented, by means of a dedicated voltage monitor device.
The PEM (together with all shelf related FRUs) are protected against wrong polarity up to

+57 VDC, but it does not block wrong polarity voltage being applied to shelf related FRUs and
to Zone 1 power wiring of payload slots.
Suppressor diodes are included in the feed chain that provide protection against a K.20 pulse
of 500 V being applied to its input (K.20 surge pulse, "Basic level", Table 7, pulse type 7.3,

500 V applied to -48 V and RTN branches at the same time against shelf ground) so that PEM
itself and other shelf related FRUs can sustain this level of pulse.
Figure 13: DC PEM
5
12713812
1 Green Fan Tray OK LED 5 RTN Input
2 Red Fan Tray Alarm LED 6 -48 V Input
3 Blue Hot Swap LED 7 Fused switch
4 Hot Swap push button