Replacing a T640 DC Power Supply Cable

You can use this procedure to replace a DC power cable for a two-input 160-A power suply, three-input 240-A DC power supply, or a four-input 240-A DC power supply.

The router has either one nonredundant power supply or two redundant, load-sharing power supplies. Each DC power cable on a redundant power supply is hot-insertable and hot-removable. When a redundant power supply is powered down, the other power supply automatically assumes the entire electrical load for the router. If you have only one power supply, you must power off the system before removing a DC power cable.

To replace a DC power supply cable, perform the following procedures:

1. Removing a T640 DC Power Supply Cable
2. Installing a T640 DC Power Supply Cable

Removing a T640 DC Power Supply Cable

1. Locate a replacement power cable that meets the specifications required for the power supply.

   Caution: A licensed electrician must attach a cable lug to the power cable that you supply. A cable with an incorrectly attached lug can damage the router.

2. Turn off the customer site circuit breaker that provides voltage to the DC power cable being replaced. Make sure that the voltage across the DC power source cable leads is 0 V and that there is no chance that the cables might become active during the removal process. Follow your site's safety and ESD procedures.
3. Remove the power cable from external DC power source.
4. Attach an electrostatic discharge (ESD) grounding strap to your bare wrist, and connect the strap to one of the ESD points on the chassis.
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.

   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 nut and washer from the terminal stud. Use a 7/16-in. (11 mm) nut driver.
8. Remove the cable lug from the terminal studs.
9. Loosen the captive screw or screws on the cable restraint on the right edge of the power supply faceplate.
10. Carefully move the power cable out of the way.

Figure 1, Figure 2, and Figure 3 show how to remove the nut and washer from the terminal stud.

Figure 1: Disconnecting a DC Power Cable from a Two-Input 160-A DC Power Supply

Figure 2: Disconnecting a DC Power Cable from a Three-Input 240-A DC Power Supply

Figure 3: Disconnecting a DC Power Cable from a Four-Input 240-A DC Power Supply

Installing a T640 DC Power Supply Cable

Note: All inputs on the two-input 160-A DC power supply in slot PEM0 must be powered by dedicated power feeds derived from feed A, and all inputs on the two-input 160-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.

Note: Only INPUT 0 and INPUT 1 are supported for the T640 router. INPUT 2 on the three-input 240-A DC power supply is not supported. Do not connect the replacement cable to INPUT 2. 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.

Note: All inputs on the four-input 240-A DC power supply in slot PEM0 must be powered by dedicated power feeds derived from feed A, and all inputs on the four-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.

1. Slide the replacement power cable lug onto the terminal stud.
2. Secure the cable lug on the DC power cable to the terminal stud, first with a washer, then with a nut. 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.

   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.

3. Route the power cable through the cable restraint.
4. Tighten the cable restraint captive screw or screws to hold the power cable in place.
5. Verify that the DC source power cabling and grounding cabling are correct, that they are not touching or blocking access to router components, and that they do not drape where people could trip on them.
6. Replace the clear plastic cover over the terminal studs on the faceplate.
7. Attach the power cable to the external DC power source.
8. Switch on the external circuit breaker that provides voltage to the DC power source cable that has been replaced.
9. For a three-input 240-A DC power supply, verify that the INPUT PRESENT LED is lit steadily, indicating that the input is receiving power.
10. Switch the circuit breakers on the power supply to the on position (|).

    Note: After a power supply is powered on, it can take up to 60 seconds for status indicators—such as the output status LEDs on the power supply, the command output display, and messages on the LCD on the craft interface—to indicate that the power supply is functioning normally. Ignore error indicators that appear during the first 60 seconds.

11. Verify that the CB ON LED on the power supply faceplate is lit steadily. The CB ON LED blinks momentarily, then lights steadily to indicate that the circuit breakers are on.
12. Verify that the DC OK LED on the power supply faceplate is lit steadily, indicating that the power cable is correctly installed and the power supply is functioning normally.

Figure 4, Figure 5, and Figure 6) show how to secure the nut and washer to the power supply.

Figure 4: Connecting a DC Power Cable to a Two-Input 160-A DC Power Supply

Figure 5: Connecting a DC Power Cable to a Three-Input 240-A DC Power Supply

Figure 6: Connecting a DC Power Cable to a Four-Input 240-A DC Power Supply