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Determining DC Power Requirements for Your MX2020 Router

 

This topic describes the MX2020 DC power subsystem, power zones, and DC power usage to help you determine which Power Supply Modules (PSMs) are suitable for your router configuration.

We recommend that you provision power according to the maximum input current listed in the power subsystem electrical specifications (see MX2000 Router DC Power Subsystem Electrical Specifications).

MX 2020 DC Power Subsystem Components

The MX2020 DC power system is comprised of two subsystems. Each subsystem provides power to:

  • 10 line-card slots

  • Nine DC Power Supply Modules (PSMs)

  • Two DC Power Distribution Modules (PDMs)

  • 20 Modular Port Concentrators (MPCs) (10 MPCs per zone)

  • Two fan trays

  • Eight Switch Fabric Boards (SFBs)

  • Two Control Board and Routing Engines (CB-REs)

Understanding Power Zones in the MX2020 DC Power Subsystem

The MX2020 DC power subsystem has two power zones: zone 0 and zone 1. Some FRUs draw power only from zone 0, some FRUs draw power only from zone 1, and some FRUs draw power from both zone 0 and zone 1. When calculating power requirements, ensure there is adequate power for each zone. Each zone needs to provide 70% of the total power required by shared FRUs. This means 140% of the power required by the FRUs is available in the two power zones combined.

There are two types of DC power subsystems available for the MX2020: a “base” DC power subsystem (MX2020-BASE-DC) and an “optimized” or premium DC power subsystem (MX2020-PREMIUM2-DC). The fan trays in an optimized DC power subsystem draw power from the power zones differently than the fan trays in a base DC power subsystem. In a base DC power subsystem, two of the four fan trays draw power from both zones. In the optimized DC power subsystem, two of the fan trays draw power from only one zone. Because of this, the optimized power subsystem requires less power. Since the two fantrays share power in a zone, they only require 100% of the power they are rated at (not 140%). This is a net savings of 40% * 1700W/fantray * 2 for the system and half that amount per power zone.

Note

70% of the total power from zone 0 + zone 1 must be provided by EACH zone in the calculation.

Note

Four DC Power Supply Modules (PSMs) per zone are mandatory for the MX2020 router with DC Power Distribution Modules (PDMs).

As illustrated in Figure 1 and described in Table 1, the power zones in the MX2020 DC base power subsystem distribute power to FRUs as follows:

  • Zone 0 powers only line card slots 0-9, and fan tray 1

  • Zone 1 powers only line card slots 10-19, and fan tray 3

  • Zone 0 + Zone 1 (both zones provide power) to CB-RE slot 0 and CB-RE slot 1, fabric card slots 0-7, and fan tray 0 and 2

Figure 1: Power Distribution in a DC Base Power Subsystem
Power Distribution in a DC Base
Power Subsystem

Table 1: MX2020 DC Power Zoning (Base DC Power Implementations)

Chassis Power Configuration

Power Zone

Power Distribution Module (PDM)

Power Supply Module (PSM)

Components Receiving Power

DC power to lower half of MX2020 components

Lower (zone 0)

PDM 0 and 1

PSM slots 0 through 8

  • MPC slots 0 through 9

    • Fan Tray 1

DC power to upper half of MX2020 components

Upper (zone 1)

PDM 2 and 3

PSM slots 9 through 17

  • MPC slots 10 through 19

  • Fan Tray 3

Zone 0 + Zone 1

  • CB-RE slot 0 and slot 1

  • SFB slots 0 through 7

  • Fan tray 0 and 2

As illustrated in Figure 2 and described in Table 2, the power zones in MX2020 DC optimized power subsystems distribute power to FRUs as follows:

  • Zone 0 powers only line card slots 1-7, and fan trays 0 and 1

  • Zone 1 powers only line card slots 10-16, and fan trays 2 and 3

  • Zone 0 and Zone 1 (both zones provide power) to CB-RE slot 0 and CB-RE slot 1, and fabric card slots 0-7

Figure 2: Power Distribution in an Optimized DC Power Subsystem
Power Distribution in an Optimized
DC Power Subsystem

Table 2: MX2020 DC Power Zoning (Optimized DC Power Implementations)

Chassis Power Configuration

Power Zone

Power Distribution Module (PDM)

Power Supply Module (PSM)

Components Receiving Power

DC power to lower half of MX2020 components

Lower (zone 0)

PDM 0 and 1

PSM slots 1 through 7

  • MPC slots 0 through 9

  • Fan tray 0 and 1

DC power to upper half of MX2020 components

Upper (zone 1)

PDM 2 and 3

PSM slots 10 through 16

  • MPC slots 10 through 19

  • Fan Tray 2 and 3

Zone 0 + Zone 1

  • CB-RE slot 0 and slot 1

  • SFB slots 0 through 7

Calculating the DC Power Requirements for Your MX2020 Router

Follow these steps to calculate the DC power requirements for your MX2020 Router configuration.

  1. Calculate the total output power required for your MX2020 FRUs.Table 3 shows the typical power usage for the MX2020 DC power subsystem FRUs.

    Table 3: Typical DC Power Usage for MX2020 Router

    Component

    Model Number

    Power Requirement (Watts) with 91% Efficiency

    Base chassis

    CHAS-BP-MX2020

     

    Fan trays (upper and lower)

    MX2000-FANTRAY

    1700 W * 4 = 6800 W

    MPC

    MPC-3D-16XGE-SFPP

    440 W * 20 = 8800 W

    ADC

    ADC

    150 W * 20 = 3000 W

    CB-RE

    RE-MX2000-1800X4

    250 W * 2 = 500 W

    SFB—slots 0 through 7

    MX2000-SFB

    220 W * 8 = 1760 W

    MX2020 DC power subsystem (upper and lower half of chassis, 60 A feeds to each PDM input)

    MX2020 DC power subsystem (upper and lower half of chassis, 80 A feeds to each PDM input)

    2100 W * 8 PSMs=16,800 W (+ 1 PSM@2100 W redundant capacity)

    2500 W * 8 PSMs=20,000 W (+ 1 PSM@2500 W redundant capacity)

    MX2020 DC power subsystem (upper and lower half of chassis, 240-V feeds to each PDM input)

    2500 W * 8 PSMs=20,000 W (+ 1 PSM@2500 W redundant capacity)

    Note

    The power reservation for the critical FRUs is 7360 W. With power droop-sharing between the two zones, the power reservation for critical FRUs is reduced to 5662 W. This number assumes a 70/30% load on the power zones when droop sharing is enabled.

  2. Evaluate the power budget, including the budget for each configuration if applicable, and check the required power against the maximum output power of available PSM options. Table 4 lists the MX2020 PSMs, their maximum output power, and unused power (or power deficit).

    Table 4: MX2020 PSM DC Output Power Budget

    Power Supply Module

    Maximum Output Power of Power Supply Module (Watt)

    Maximum Output Power for System (Watt)—including redundant capacity

    MX2020 DC PSM 60 A (feed to each input)

    2100

    37,800

    MX2020 DC PSM 80 A or DC PSM (240 V China) (feed to each input)

    2500

    45,000

  3. Calculate input power. Divide the total output requirement by the efficiency of the PSM. Refer to Table 5.

    Table 5: Calculating DC Input Power

    Power Supply Module

    Power Supply Module Efficiency

    Output Power Requirement (Watt)—per PSM

    Input Power Requirement (Watt)—per PSM

    MX2020 DC PSM 60 A

    91%

    2100

    2307

    MX2020 DC PSM 80 A or DC PSM (240 V China)

    91%

    2500

    2747

  4. Calculate thermal output (BTUs) for cooling requirements. Multiply the input power requirement (in watts) by 3.41. Refer to Table 6.

    Table 6: Calculating DC Thermal Output (BTUs)

    Power Distribution Module

    Thermal Output (BTUs per hour)

    MX2020 DC PDM

    34.5 KW divided by 0.91 * 3.41 = 129,280 BTU/hr (Zone 0 output. The calculation method for Zone 1 is the same as for Zone 0).

    34.5 KW of output power consumed by the chassis. This is the maximum output the chassis can consume in a redundant configuration. The input power is 34.5 divided by 0.91 = 37.9 KW.