Managing Power Systems 33
■ The EME may shut down selected interface modules in an attempt to
bring installed module power consumption under the now-reduced
power budget.
In power fault-tolerant mode, power equivalent to one power supply is
held in reserve. This reserve power is not available to installed modules
unless a power supply fails, or if you switch the power mode from power
fault-tolerant mode to power non-fault-tolerant mode.
While the chassis is running in power fault-tolerant mode:
■ All installed power supplies are functioning and contributing power to
the chassis and modules. No single power supply is a dedicated
standby power supply. Rather, a factory-defined power limit ensures
that power that is equivalent to at least one power supply is available
to replace power lost if a power supply fails.
■ The amount of power that installed modules require must not be
greater than the number of installed power supplies, minus one (n-1).
When you reserve power that is equivalent to one power supply in
power fault-tolerant mode, the failure of a single power supply has no
impact on installed modules that are already powered on.
If a power supply fails while the chassis is running in fault-tolerant mode:
■ The EME automatically disables fault-tolerant mode.
■ Power formerly reserved is made available to modules to prevent them
from powering off.
■ All modules that had power before the power supply failure continue
to receive power without interruption.
■
Upon power supply recovery (or replacement), the EME automatically
reenables fault-tolerant mode.
Overheat Power Down Mode
An overheat condition exists when one of the chassis temperature
sensors detects a chassis internal operating temperature that exceeds a
predefined threshold. The allowable ambient temperature operating
range is 0 °C through 50 °C (32 °F through 122 °F). The default threshold
setting is fixed at an upper limit of 60 °C (140 °F) or higher to prevent
module damage.
