The DC power shelf is the enclosure that houses two DC power entry modules (PEMs), the alarm module, and power distribution connections and wiring. The DC power shelf is installed in the FCC from the front and plugs into the chassis power interface connector panel.
Figure 9. DC Fixed Configuration Power Shelf
The DC power shelf physical dimensions are:
Height—6.2 in. (15.8 cm)
Width—20 in. (50.8 cm)
Depth—25 in. (63.5 cm)
Weight—38 lb (17.24 kg) (without DC PEMs)
Each power shelf has four input power connectors to connect input DC power (nominal –48 VDC or –60 VDC, 60 A). Each connector consists of two terminals (– and +). Each terminal consists of two M6 threaded studs, 0.6 inches long, and centered 0.625 inches apart. The terminals have a safety cover.
A service processor is located in the alarm module that monitors the condition of each PEM and provides status signals that indicate the health of the power supplies.
This figure is a block diagram of the connections between the DC power shelves and FCC. See the Cisco CRS Carrier Routing System Fabric Card Chassis Installation Guide for information about the input power connections to the DC power shelf.
Figure 10. DC Power Shelves in a Fixed Configuration FCC
Each DC power shelf supports two PEMs. Each power shelf accepts four pairs of 60 A battery feeds. Input DC power enters the power shelf and is processed by the PEMs before being distributed to the chassis backplane. The PEMs perform inrush current limiting, EMI filtering, surge protection, and circuit isolation on the input DC power, and then distribute the power to either the A or B bus bar in the chassis backplane.
To provide 2N redundancy, one DC power shelf powers the A bus and the other shelf powers the B bus. Load zones in the chassis backplane provide power from both the A and B buses to each card and module in the chassis. For detailed information about how power is distributed through the chassis, see the Fixed Configuration Power Architecture and the Fixed Configuration Chassis Load Zones.
A service processor is located in the alarm module that monitors the condition of each PEM and provides status signals to indicate the health of the power supplies.
This figure shows the wiring of a DC power shelf. Four sets of two-wire 60 A DC power are wired into the DC power shelf at a terminal block. The DC power is then routed through the shelf circuit breaker to the two DC PEMs (A0 and A1) in the power shelf. The DC PEMs are passive units that provide power conditioning to the system. PEMs provide circuit protection, EMI filtering, soft-start circuitry, and OIR for the system. Each DC PEM powers two of the chassis load zones.
Figure 11. DC Power Wiring (Fixed Configuration)