Siemens SIMATIC S7-400 Reference Manual page 47

BAF lights up if the backup voltage on the backplane bus is too low. Possible causes of this
include:
● Battery (batteries) empty or battery polarity has been reversed.
● External supply via CPU or receive IM is defective or supply from secondary power supply
module is defective or missing.
● Short-circuit or overload on the battery voltage.
Note
Due to internal capacities, if you remove the battery or switch off the external supply, some
time may elapse before BAF, BATT1F, or BATT2F lights up.
Function of the operator controls of the power supply modules
Table 3-5
FMR button
Standby switch
Switches
BATT.INDIC
Battery compart‐
ment
Power connection
Cover
The battery compartment, battery selector switch, voltage selector switch and power
connection are housed under one cover. The cover must remain closed during operation in
order to protect these operator controls and to prevent static electricity from affecting the
battery connections.
Discharge your body before you start taking any measurements on a module. Do so by
touching grounded metallic parts. Always use grounded measuring instruments.
S7-400 Automation System Module Data
Reference Manual, Ausgabe 11/2016, A5E00850736-08
Function of the operator controls of the power supply modules
Control
For acknowledging and resetting a fault indicator after correcting the fault
Switches the output voltages (5 V VDC24 VDC) to 0 V by intervening in the
control loop (no mains disconnection).
Output voltages at nominal value
●
Output voltage 0 V
●
Used for setting LEDs and battery monitoring
Where one battery can be used (PS 407 4A, PS 405 4A):
● OFF: LEDs and monitor signals inactive
● BATT: BAF/BATTF LEDs and monitor signals active
Where two batteries can be used (PS 407 10A, PS 407 20A, PS 405 10A, PS
405 20A):
● OFF: LEDs and monitor signals inactive
● 1 BATT: Only BAF/BATT1F LEDs (for battery 1) active.
● 2 BATT: BAF/BATT1F/BATT2F LEDs (for batteries 1 and 2) active.
For backup battery (batteries)
3-pin connector for the power main
(do not pull and plug under power)
Power supply modules
3.4 Operator controls and indicators
Function
47