Juniper SRX5600, Руководство по оборудованию, Страница: 222 / 483

Figure 104: DC High-Capacity Power Supply Input Mode Switch
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5. Remove the clear plastic cover protecting the terminal studs on the faceplate.
6. 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.
7. Remove the nuts and washers from the terminal studs. (Use a 7/16-in. (11 mm) nut driver or socket
wrench.)
8. Secure each power cable lug to the terminal studs, first with the flat washer, then with the nut (see
Figure 105 on page 226 ). Apply between 23 lb-in. (2.6 Nm) and 25 lb-in. (2.8 Nm) of torque to each nut.
(Use a 7/16-in. (11 mm) nut 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.
The DC power supplies in slots PEM0 and PEM1 must be powered by dedicated power feeds derived
from feed A, and the DC power supplies in slots PEM2 and PEM3 must be powered by dedicated power
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