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DC Power Specifications and Requirements

DC Power System Electrical Specifications

Table 30 lists the DC power system electrical specifications.

Table 30: DC Power System Electrical Specifications

Item	Specification
DC input voltage	Operating range: –40.5 to –72 VDC
DC system current rating	58 A (32 A per feed) @ –48 VDC
Maximum DC input power	2774 W

DC Power Circuit Breaker Specifications

Each DC power supply has a single DC input (–48 VDC and return) that requires a dedicated facility circuit breaker. We recommend that you use a customer site circuit breaker rated for 40 A (–48 VDC) minimum for each DC power supply, or as required by local code. Doing so enables you to operate the services gateway in any configuration without upgrading the power infrastructure.

If you plan to operate a DC-powered services gateway at less than the maximum configuration and do not provision a 40 A (–48 VDC) circuit breaker, we recommend that you provision a circuit breaker for each DC power supply rated for at least 125% of the continuous current that the system draws at –48 VDC, or as required by local code.

DC Power Supply Electrical Specifications

Table 31 lists the DC power supply electrical specifications. For DC power system electrical specifications, see Table 30.

Table 31: DC Power Supply Electrical Specifications

Item	Specification
Maximum output power	1600 W
DC input voltage	Minimum: –40.5 VDC Nominal: –48 VDC Operating range: –40.5 to –72 VDC
DC input current rating	33.3 A @ –48 V nominal operating voltage
Internal Supplementary Protector	40 A

The DC power supplies in PEM0 and PEM1 must be powered by dedicated power feeds derived from feed A, and the DC power supplies in PEM2 and PEM3 must be powered by dedicated power feeds derived from feed B. This configuration provides the commonly deployed A/B feed redundancy for the system.

Power Requirements for DC-Powered Services Gateways

Note: If you plan to operate a maximally configured DC-powered services gateway, we recommend that you provision 58 A (32 A per feed) @ –48 VDC for the system.

If you do not plan to provision 58 A (32 A per feed) @ –48 VDC for the system, you can use the information in Table 32 and Table 33 to calculate the power consumption @ –48 VDC, and thermal output for various hardware configurations.

Table 32 lists the power requirements for base DC-powered devices operating under typical voltage conditions.

Table 32: DC-Powered Base System Requirements

DC Power Supply Configuration	Power Requirement (Watts)	Current Requirement (Amps @ –48 VDC)
Nonredundant configuration includes two DC power supplies, midplane, craft interface, and the fan tray (running at normal speed)	135 W (approximate)	2.8 A (approximate)
Redundant configuration includes four DC power supplies, midplane, craft interface, and the fan tray (running at normal speed)	180 W (approximate)	3.8 A (approximate)

Table 33 lists the power requirements for various hardware components when the services gateway is operating under typical voltage conditions.

Table 33: Component Power Requirements

Component	Power Requirement (Watts)	Current Requirement (Amps @ –48 VDC)
Fan tray (full speed) – Fan tray (normal speed)	110 W – 80 W =30 W	0.6 A
SCB	150 W	3.1 A
Routing Engine	90 W	1.9 A
IOC—Generalized typical value	312 W	6.5 A
IOC—Generalized maximum value	365 W	7.6 A
SPC—Generalized typical value	213 W	4.4 A
SPC—Generalized maximum value	351 W	7.3 A

Use the information in Table 32 and Table 33 to calculate power consumption for various hardware configurations, input current from a different source voltage, and thermal output, as shown in the following examples. These examples use generalized values per IOC. Typical power consumption for DC-powered devices:

Minimum DC-powered configuration:
Base device (nonredundant) + 1 SCB + 1 Routing Engine + 1 IOC + 1 SPC—Generalized typical value = 2.8 A + 3.1 A + 1.9 A + 6.5 A +4.4 A = 18.7 A @ –48 VDC =898 W
Maximum DC-powered configuration:
Base device (redundant) + fan tray at full speed + 2 SCBs + 1 Routing Engine + 5 IOCs + 1 SPC—Generalized maximum value = 3.8 A + 0.6 A + 2(3.1) A + 1.9 A + 5(7.6 A) + 7.3 A= 3.8 A + 0.6 A + 6.2 A + 1.9 A + 38 A + 7.3 A= 57.8 A @ –48 VDC = 2774 W DC
Input current from a DC source other than –48 VDC (based on maximum configuration; applies to DC power supply only):
(–54 VDC input) * (input current X) = (–48 VDC input) * (input current Y) 54 * X = 48 * 57.8 A X = (48 * 57.8 A)/54 = 51.4 A
Thermal output for maximally configured DC-powered services gateway:
Watts DC * 3.41= BTU/hr 2774 W * 3.41 = 9459 BTU/hr

DC Power Cable Specifications

Figure 74 shows a typical DC source cabling arrangement.

Figure 74: Typical DC Source Cabling to the Services Gateway

Image g030205.gif

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.

Warning: For field-wiring connections, use copper conductors only.

For other electrical safety information, see Electrical Safety Guidelines and Warnings.

Caution: Power cords and cables must not block access to services gateway components or drape where people could trip on them.

For a description of the DC power supply, see , as opposed to the DC power configuration (see DC Power Supply for more information) For instructions on connecting the DC power and grounding cables during initial installation, see Connecting Power to a DC-Powered Services Gateway. For instructions on replacing a DC power cable, see Replacing a DC Power Supply Cable.

DC Power Cable Lug Specifications

The accessory box shipped with the services gateway includes the cable lugs that attach to the terminal studs of each power supply (see Figure 75).

Figure 75: DC Power Cable Lug

Image g001188.gif

Caution: Before services gateway installation begins, a licensed electrician must attach a cable lug to the grounding and power cables that you supply. A cable with an incorrectly attached lug can damage the services gateway.

DC Power Cable Specifications

Table 34 summarizes the specifications for the power cables, which you must supply.

Table 34: DC Power Cable Specifications

Cable Type	Quantity and Specification
Power	Eight 6-AWG (13.3 mm²), minimum 60°C wire, or as permitted by the local code

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