Connecting DC Power to a T640 Router with Three-input 240-A DC Power Supplies (2-INPUT Mode)

To connect the DC source power cables to the T640 router:

1. 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 electrostatic discharge (ESD) grounding strap to your bare wrist, and connect the strap to one of the ESD points on the chassis.
3. Verify that the input mode switch is correctly set to 2–INPUT mode. See Setting the Input Mode Switch on a Three-Input 240-A DC Power Supply for a T640 Router.
4. Replace the cable restraint, if needed. See Replacing the T640 Cable Restraint on a Three-Input 240-A DC Power Supply.
5. Switch the circuit breakers on the power supply faceplate to the OFF position (O).
6. Remove the clear plastic cover protecting the terminal studs on the faceplate.
7. Remove the nut and washer from the power terminal studs for INPUT O and INPUT 1. INPUT 2 is not supported for the T640 router. If no washers and nuts are already installed, they should be in the accessory box.
8. Secure the cable lug on the DC power cable to the terminal studs for INPUT O and INPUT 1, first with a washer, then with a nut (see Figure 1). Use a 7/16-in. (11 mm) nut driver or wrench to tighten the nut. Apply between 23 lb-in. (2.6 Nm) and 25 lb-in. (2.8 Nm) of torque to each nut):
   1. Secure each positive (+) DC source power cable lug to a RTN (return) terminal.
   2. Secure each negative (–) DC source power cable lug to a –48V (input) terminal.

   Note: INPUT 0 and INPUT 1 on the three-input 240-A DC power supply in slot PEM0 must be powered by dedicated power feeds derived from feed A, and INPUT 0 and INPUT 1 on the three-input 240-A DC power supply in slot PEM1 must be powered by dedicated power feeds derived from feed B. This configuration provides the commonly deployed A/B feed redundancy for the system. INPUT 2 is not used for the T640 router.

   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.

9. Loosen the captive screw or screws on the cable restraint on the right edge of the power supply faceplate.
10. Route the DC power cables through the cable restraint.
11. Tighten the cable restraint captive screw or screws to hold the power cables in place.
12. Verify that the power cabling is correct, that the power cables are not touching or blocking access to router components, and that they do not drape where people could trip on them.
13. Replace the clear plastic cover over the terminal studs on the faceplate.

    Figure 1: Connecting DC Power to a Three-Input 240-A DC Power Supply in 2–INPUT Mode