Juniper MX480, Руководство по оборудованию

Страница: 208 / 420

To connect the DC source power cables to the router:
1.
Switch off the dedicated customer site circuit breakers. Ensure that the voltage across
the DC power source cable leads is 0 V and that there is no chance that the cable
leads might become active during installation.
2.
Attach an ESD grounding strap to your bare wrist and connect the strap to one of the
ESD points on the chassis.
3.
Move the DC circuit breaker on the power supply faceplate to the off (
O
) position.
4.
Remove the clear plastic cover protecting the terminal studs on the faceplate.
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 large resistance (indicating an open circuit) to chassis ground
is –48V.
•
The cable with very low resistance (indicating a closed circuit) to chassis ground is
RTN.
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
terminal studs on each power supply.
6.
Remove the nut and washer from each of the terminal studs. (Use a 7/16-in. [11 mm]
nut driver or socket wrench.)
7.
Secure each power cable lug to the terminal studs, first with the flat washer, then
with the nut (see
Figure 72 on page 210 ). Apply between 23 lb-in. (2.6 Nm) and 25 lb-in.
(2.8 Nm) of torque to each nut. Do not overtighten the nut. (Use a 7/16-in. [11 mm]
torque-controlled driver or socket wrench.)
a. Secure each positive (+) DC source power cable lug to the RTN (return) terminal.
b. Secure each negative (–) DC source power cable lug to the –48V (input) terminal.
CAUTION: Ensure that each power cable lug seats flush against the surface
of the terminal block as you are tightening the nuts. Ensure that each nut
is properly threaded onto the terminal stud. The nut should be able to spin
Copyright © 2019, Juniper Networks, Inc. 208
MX480 Universal Routing Platform Hardware Guide