Dc Rack Configuration; Dc Power Distribution And Ground Illustration - IBM T00 Service Manual

DC Rack Configuration

The dc rack must be connected to an external -48 V dc power source. The -48 V dc power source must
be electrically isolated from the ac power source. In addition, the -48 V dc source must be grounded.
The dc rack can be connected to one or two -48 V dc power source to provide redundant power backup. If
two power sources are used, one power source is connected to bus bar A and the other to bus bar B.
The circuit breakers in the dc power distribution panel are attached to two dc power bus bars (bus bar A,
and bus bar B). As described above, these bus bars can be connected either to a common power source
or to separate power sources (redundant power). Typically, a dc power distribution panel contains two
matching banks of circuit breakers. Each bank of circuit breakers is connected to either bus bar A or bus
bar B. The -48 V dc power supply of each drawer is connected to one circuit breaker in each bank of the
-48 V dc power distribution panel. Thus, when one of the -48 V dc power sources fails, the devices in the
rack still receive power from the other source.
The exact configuration of the dc power distribution panel depends on the configuration of drawers and
devices installed in the rack. Illustrations on the following pages show typical examples of power
distribution for a standalone rack containing a CPU drawer and device drawers.
Note: Before you service the dc power distribution panel, use care to first determine the exact power
configuration and distribution.
The following illustration shows a typical dc power distribution panel (external view).
1 Cable Channel Cover
2 Terminal Block (Both Sides)

DC Power Distribution and Ground Illustration

The following illustration is for reference only and shows the power distribution in a typical -48 V dc rack
connected to two -48 V dc power sources. Each power supply in the CPU drawer is connected to a
separate circuit breaker in the -48 V dc power distribution panel.
3 Power Distribution Panel
4 Front of Rack
Chapter 1. Reference Information
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