5. Remove the plastic cable cover from the power input terminals by using the Phillips (+) screwdriver, number 2, to
loosen the screws (see
Figure 33: Removing the Plastic Cable Cover on a JNP10K-PWR-DC2 Power Supply
g100594
6. Remove the nuts from each DC power input terminal, using the 13/32 in. (10 mm) nut driver or socket wrench to
loosen the nuts.
7. 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.
8. 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.
37