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Power Entry Module (PEM)
31
R1.0, October 2018
8 Power Entry Module (PEM)
8.1 Introduction
Two pluggable redundant Power Entry Modules (PEMs) are located at the rear
bottom side of the Shelf. Each PEM provides power terminals for a 210 A power
feed.
Each input feed is divided internally at the PEM in 6 output branches toward the
backplane. In this way, each PEM has 1 input feed and 6 output branches.
Over current protection is provided by 50 A fuses in each output branch. The
segmentation is shown in
.
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 -40 VDC to -72 VDC.
In each power feed, input voltage and measurement is implemented, by means
of dedicated voltage monitor device.
The PEM provides:
•
PCA9555 I/O device for voltage monitoring and Hot Swap functionality
•
LM75 temperature sensor
•
24LC256 FRU SEEPROM
•
2 INA220B Current/Voltage measurement devices
These devices are connected to the I²C-bus via an LTC4300 I²C buffer. In order
to guarantee a galvanic insulation, I²C-bus insulation devices have provided for
the INA220B Current/Voltage Monitors.
To detect a blown fuse, the voltages after the fuses are monitored by threshold
comparators. The threshold comparators are coupled to the PCA9555 chip
Hazardous voltage!
Before working ensure that the power is removed from the power connection
cables. When the system is powered on, do NOT touch the power terminals.
The Shelf can be powered using a regular telecommunication power supply of
-48/-60 VDC with a VDC return. The specified voltage range is from -40 VDC
to -72 VDC.The Shelf supports redundant power supplies but the two supplies
should be independently powered.
