Maintaining the T640 Power Supplies

Purpose

For optimum router performance, verify the condition of the power supplies.

Action

• Make sure that the power and grounding cables are arranged so that they do not obstruct access to other router components.
• The power supplies require an unobstructed airflow at both the front and rear of the chassis. Periodically check the site to ensure that both the air intake at the bottom front of the chassis and the exhaust from the power supply faceplates are unobstructed.
• Periodically inspect the site to ensure that the grounding and power cables connected to the router are securely in place and that no moisture is accumulating near the router. To review grounding and site wiring requirements for the router, see T640 Chassis Grounding Cable and Lug Specifications and Site Electrical Wiring Guidelines for M Series and T Series Routers.
• Regularly inspect the air filters on each power supply for dust and debris, and replace the side filter on AC power supplies or front filter element on AC and DC power supplies every 6 months. To replace a power supply front air filter element, see Replacing a Front Air Filter Element on a T640 AC or DC Power Supply. To replace a side air filter, see Replacing a Side Air Filter on a T640 AC Power Supply .
• Routinely check the LEDs on the DC power supply faceplates. If the DC OK LEDs are lit steadily, the power supplies are functioning normally.
• Routinely check the LEDs on the AC power supply faceplates. If the AC OK LEDs are lit, the AC terminal blocks are receiving power. If the DC OK LEDs are lit, the AC power supplies are functioning normally.
• Check the red and yellow alarm LEDs and the LCD on the craft interface. Power supply failure or removal triggers an alarm that causes one or both of the LEDs to light and an error message to appear on the LCD. You can display the associated error messages by issuing the CLI command:
  user@host> show chassis alarms

  For a list of possible alarm messages, see Troubleshooting the T640 Power System.

• Issue the show chassis environment pem command to check the status of the power supplies. For DC- powered routers, the output is similar to the following:
  user@host> show chassis environment pem

  PEM 0 status:
    State                      Online
    Temperature                24 degrees C / 75 degrees F             
    DC Input:                  OK
    DC Output             Voltage   Current       Power    Load
        FPC 0               0         0             0        0      
        FPC 1               54558     981           53       7      
        FPC 2               54558     2800          152      20     
        FPC 3               54700     2225          121      16     
        FPC 4               54375     2387          129      17     
        FPC 5               54308     3543          192      25     
        FPC 6               54558     1287          70       9      
        FPC 7               54616     2650          144      19     
        SCG/CB/SIB          54150     181           9        0      
  

  PEM 1 status:
    State                      Online
    Temperature                23 degrees C / 73 degrees F             
    DC Input:                  OK
    DC Output             Voltage   Current       Power    Load
        FPC 0               0         0             0        0      
        FPC 1               50691     0             0        0      
        FPC 2               50766     0             0        0      
        FPC 3               50725     0             0        0      
        FPC 4               50725     0             0        0      
        FPC 5               50766     0             0        0      
        FPC 6               50808     0             0        0      
        FPC 7               50625     0             0        0      
        SCG/CB/SIB          50300     0             0        0      
  

  The current sharing between DC power supplies relies on equal voltages at the input terminals of the power supplies. However, if the voltages do not match, the router operates normally as long as the DC input voltages are within the operating range provided in T640 DC Power System Electrical Specifications .

  • For the three-input 240-A DC power supplies in 2–INPUT mode and the two-input 160-A DC power supplies, system power is divided into two load zones. One load zone consists of INPUT 0 of PEM0 and PEM1. The other load zones consist of INPUT 1 of PEM0 and PEM1. Load sharing occurs between the two power supplies for each load zone. Therefore, the input voltage for the inputs in each load zone must be equal in both power supplies for current sharing. For example, the input voltage for INPUT 0 of PEM0 and the input voltage for INPUT 0 of PEM1 must be the same for current sharing to occur within that load zone.
  • For the four-input 240-A DC power supplies, system power is divided into four load zones. One load zone consists of INPUT 0 of PEM0 and PEM1. The three other load zones consist of INPUT 1, INPUT 2 and INPUT 3 of PEM0 and PEM1. Load sharing occurs between the two power supplies for each load zone. Therefore, the input voltage for the inputs in each load zone must be equal in both power supplies for current sharing. For example, the input voltage for INPUT 0 of PEM0 and the input voltage for INPUT 0 of PEM1 must be the same for current sharing to occur within that load zone.

  For further description of the output from the commands, see the Junos OS System Basics and Services Command Reference .

  For AC-powered routers, the output is similar to the following:

  user@host> show chassis environment pem

  PEM 1 status:
  
    State                      Online
  
    Temperature                33 degrees C / 91 degrees F             
  
    AC Input:                  OK
  
    DC Output           Voltage(mV) Current(mA)  Power(W)  Load(%)
  
        FPC 0               55183     7056          389      51     
  
        FPC 1               55633     7018          390      52     
  
        FPC 2               55533     5187          288      38     
  
        FPC 3               55533     7081          393      52     
  
        FPC 4               55508     6612          367      48     
  
        FPC 5               55791     7337          409      54     
  
        FPC 6               55675     2593          144      19     
  
        FPC 7               55608     7600          422      56     
  
        SCG/CB/SIB          55308     5600          309      25