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M320 DC Power Supplies Description

 

In the DC power configuration, the router contains either two or four DC power supplies, located at the lower rear of the chassis in slots PEM0 through PEM3 (top to bottom).

If only two DC power supplies are installed, the power supplies in either slots PEM0 and PEM1 or slots PEM2 and PEM3 can provide full power to the router. You can upgrade your DC power supply from two to four power supplies for full redundancy.

Note

Except during upgrade, all DC power supplies installed in the chassis must be the same model number, either all isolated or all nonisolated DC power supplies. Using both isolated and nonisolated DC power supplies during normal operations prevents load sharing.

Nonisolated DC Power Supply

Each nonisolated power supply consists of a single DC input (-48 VDC and return), a circuit breaker, a fan (each power supply is cooled by its own internal cooling system), and LEDs to monitor the status of the power supply. Each nonisolated power supply weighs approximately 10 lb (4.5 kg).

Isolated DC Power Supply

Each isolated power supply consists of a single DC input (-48 VDC and return), a circuit breaker, a fan (each power supply is cooled by its own internal cooling system), and LEDs to monitor the status of the power supply. Each isolated power supply weighs approximately 10 lb (4.5 kg).

Note

The Isolated DC power supply is designed to be more resilient to power irregularity such as noise or surge in power environment.

Components Powered by Each Power Supply Slot

The DC power supplies in the slots indicated provide power to the components listed in Table 1.

Table 1: Components Powered by Each DC Power Supply Slot

Slot

Provide Power to These Components

PEM0 and PEM2

FPCs in slots FPC3 through FPC7

PEM1 and PEM3

FPCs in slots FPC0 through FPC2, SIBs, CBs, and Routing Engines, and fan trays.

DC Power Supply Load Sharing and Fault Tolerance

When the router is fully configured with four DC power supplies:

  • The DC power supplies provide full redundancy

  • The DC power supply in PEM2 serves as the backup to the DC power supply in slot PEM0.

  • DC power supply in PEM3 serves as the backup to the DC power supply in slot PEM1

  • Load sharing occurs between the DC power supplies installed in slots PEM0 and PEM2

  • Load sharing occurs between the DC power supplies in slots PEM1 and PEM3

Note

Isolated DC power supplies share current over the full input operating voltage range. The current sharing between nonisolated power supplies relies on equal voltages at the power supply input terminals.