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    M40e Router Power Requirements

    The router uses either AC or DC power. There are two load-sharing, pass-through power supplies located at the bottom rear of the chassis, as shown in M40e Chassis Description. The power supplies connect to the midplane, which distributes power to router components according to their individual voltage requirements. When the power supplies are installed and operational, they automatically share the electrical load. If a power supply stops functioning for any reason, the remaining power supplies instantly begin providing all the power the router needs for normal functioning and can provide full power indefinitely.

    Caution: Mixing AC and DC power supplies is not supported and prevents the router from booting. If two power supplies are installed, they must either both be AC or both DC.

    A circuit breaker box must be installed on a DC-powered router, whereas a circuit breaker is incorporated into each AC power supply.

    Table 1 lists the AC and DC power system electrical specifications. Table 2 lists the power requirements for various hardware components when the router is operating under typical voltage conditions. For PIC power requirements, see the M40e Multiservice Edge Router PIC Guide.

    Table 1: M40e Power System Electrical Specifications



    AC input voltage

    Operating range: 180 to 264 VAC

    Nominal: 200 VAC, 208 VAC, 220 VAC, 240 VAC

    AC input line frequency

    47 to 63 Hz

    AC system current rating

    15 A @ 200 VAC

    13 A @ 240 VAC

    DC input voltage

    Operating range: –40.5 to –72 VDC

    Note: If the input voltage from the DC power source drops below –40.5 VDC, the platform automatically shuts down. During automatic shutdown, the circuit remains active. When the input voltage returns to –42.75 VDC, the platform automatically starts up again and the system returns to normal operation within 30 minutes. No operator intervention is required.

    Nominal: –48 VDC, –60 VDC

    DC system current rating

    54 A @ –48 VDC (nominal)

    DC maximum system input power

    2445 W

    Table 2: M40e Component Power Requirements


    Power Requirement (Amps)

    Base system (cooling system, power supplies, and craft interface)

    7-10 A @ –48 V

    Host module (Routing Engine and MCS)

    1.3 A @ –48 V

    M40e Type 1 and Type 2 FPCs

    1.6 A @ –48 V


    0.2 A @ –48 V


    1.3 A @ –48 V

    You can use the information in Table 2 to calculate power consumption for various hardware configurations, input current from a different source voltage, and thermal output, as shown in the following examples for a DC-powered router. These examples use generalized values for PICs. For PIC power requirements, see the M40e Multiservice Edge Router PIC Guide.

    • Power consumption for minimum configuration:

      Base system + 1 FPC + 1 SFM + 1 host module + 2 PCGs + 4 PICs =

      7 A + 1.6 A + 1.3 A + 1.3 A + 2(0.2 A) + 4(0.625 A) =

      7 A + 1.6 A + 1.3 A + 1.3 A + 0.4 A + 2.5 A = 14.1 A @ 48 V = 677 W DC

    • Power consumption for maximum configuration:

      Base system + 8 FPCs + 4 SFMs + 2 host modules + 2 PCGs + 32 PICs =

      10 A  + 8(1.6 A) + 2(1.3 A) + 2(1.3 A) + 2(0.2 A) + 32(0.625 A)  =

      10 A + 12.8 A + 2.6 A + 2.6 A + 0.4 A + 20 A = 48.4 A @ 48 V = 2323 W DC

    • Input current from a DC source other than 48 V (based on maximum configuration; applies to DC power supply only):

      (54 VDC input) x (input current X) = (48 VDC input) x (input current Y)

      54 x X = 48 x 50.8 A

      X = 48 x 50.8 A/54 = 45.2 A

    • System thermal output for maximally configured AC-powered router:

      Watts DC/85% AC PEM efficiency/0.293 = BTU/hr

      2323/0.85/0.293 = 9327 BTU/hr

    • System thermal output for maximally configured DC-powered router:

      105% of Watts DC/0.293 = BTU/hr

      1.05 x 2323/0.293 = 8325 BTU/hr

    Note: As indicated in the preceding list of calculations, even when maximally configured the router requires no more than 54 A of power.

    If you plan to operate a maximally configured DC-powered router, we recommend that you provision at least 54 A @ 48 VDC and use a facility circuit breaker rated for 70 A minimum. Doing so enables you to operate the router in any configuration without upgrading the power infrastructure, and allows the router to function at full capacity using one power supply.

    If you plan to operate a DC-powered router at less than the maximum configuration and do not provision a 70 A circuit breaker, we recommend that you provision a circuit breaker rated for at least 125% of the continuous current that the system draws at 48 V.

    Published: 2010-10-28