Juniper EX4500-40F-BF, Полное руководство по оборудованию, Страница: 165 / 294

NOTE: It might be necessary to slide each power supply partially out of
the chassis to easily connect the DC power source cables to the DC power
input terminals. See
“Removing a DC Power Supply from an EX4500
Switch” on page 183 .
Figure 48: Remove Plastic Cover from Terminal Block
g020862
DC terminal block
DC terminal
block cover
3.
Remove the locking screws from each DC power input terminal, using the screwdriver.
4.
Ensure that the power source circuit breaker is open so that the voltage across the
DC power source cable leads is 0 V and that the cable leads do not become active
while you are connecting DC power.
5.
Verify that the DC power cables are correctly labeled before making connections to
the power supply. In a typical power distribution scheme where the return is connected
to chassis ground at the battery plant, you can use a multimeter to verify the resistance
of the
–48V and RTN DC cables to chassis ground:
• The cable with very high resistance (indicating an open circuit) to chassis ground
is negative (–) and will be installed on the
–48V (input) DC power input terminal.
•
The cable with very low resistance (indicating a closed circuit) to chassis ground is
positive (+) and will be installed on the
RTN
(return) DC power input terminal.
CAUTION: You must ensure that power connections maintain the proper
polarity. The power source cables might be labeled (+) and (–) to indicate
their polarity. There is no standard color coding for DC power cables. The
color coding used by the external DC power source at your site determines
the color coding for the leads on the power cables that attach to the DC
power input terminals on each power supply.
6.
Install each power cable lug on the DC power input terminal, securing it with the locking
screw, (see
Figure 49 on page 148 ). Apply between 9 in.-lb (1.1 Nm) and 12 in.-lb (1.3 Nm)
of torque to tighten each locking screw.
147 Copyright © 2015, Juniper Networks, Inc.
Chapter 11: Connecting the Switch