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20 Power System: Description/Calculating
Power Usage
This chapter describes the modular power system and explains how to calculate power usage for
your server.
Warnings and Cautions
Only a qualified service technician is authorized to remove the server covers and to access any of
the components inside the server. Before removing the covers, see “Safety Guidelines” on
page 115.
AC Input Power
The server can operate with input voltages of 200-240VAC or 100-120VAC. A jumper located on
the midplane selects the input voltage at which the server will operate. The jumper also
enables/disables the brown out recovery feature that aids server startup during low AC input
voltage conditions.
JP1 Position
Valid AC Input
Range AC Mains Brown Out Feature
Installed
200-240VAC or
100-120VAC
15A
15A
Disabled
Disabled
Removed
200-240VAC 15A Enabled
Enabling the brown out feature ensures that all power supplies will turn on when the AC input
voltage reaches at least 180VAC following an AC main brown out condition.
Disabling the brown out feature can cause power problems when the system tries to recover from a
brown out condition. The problems that can result depend on server AC input voltages.
• For 100-120VAC input power after a brown out: AC input voltage may slowly rise to its
nominal level and because of slight differences in power supply turn on thresholds at 90V, one
power supply may turn on before the others. This power supply will most likely see too large
a DC load and shut down (other power supplies may do the same), removing all DC voltages
from the server.
• For 200-240VAC input power after a brown out: AC input voltage may slowly rise to its
nominal level and the power supplies turn on at 90V doubling the current load on the AC main
and causing them to trip.
• For power supply input voltages see Table 20-3.