4.3.5
Description of Internal
Sequences in the Power
Supply Unit
Given in this section is background information on internal sequences
in the power supply unit.
Behavior upon failure of the
system supply
When the system supply fails
The behavior of the power supply unit after a system supply failure is
governed by the duration of the failure:
IF the system
supply failure...
THEN...
lasts up to
20 ms,
the PSU output voltages are within tolerance
ranges; no indication appears on the front plate
and no signal is sent to the S5 bus.
lasts longer than
20 ms,
a data save routine is initiated on the CPU/CPUs
and an output inhibit is issued.
If the 5 V supply drops below
the 4.75 V limit
If the 5 V supply drops below the lower limit (4.75 V), the power
supply also activates the output inhibit, and the data save routine on
the CPU is thus initiated.
Redundant data backup
Your CC and EU 185 are provided with a lithium battery for data
backup, and the power supply unit also contains a rechargeable
battery.
In the event of system supply failure or switch-off, data backup is
guaranteed by the lithium battery and, in the event of battery failure,
by the rechargeable battery which is constantly being charged to its
full capacity.
After replacing a defective lithium battery, the new one resumes data
backup and on exchanging the battery you should acknowledge the
error indication.
As the rechargeable battery is also removed when the power supply
unit is replaced, data backup is temporarily performed by the lithium
battery.
Power Supply Units
System Manual
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C79000-B8576-C199-03