9 Operation
SMA Solar Technology AG
Operating Manual STPx0-3SE-40-BE-en-10 81
Procedure:
1. In the parameter group Device > Operation, select the parameter Operating mode of the
battery-backup system and set it to Automatic so that the battery-backup operation is
activated automatically in the event of a grid failure.
2. Set the parameter Minimum width of backup power area in the parameter group Battery
> Areas of application. The value indicates the percentage of battery charge to be retained
for battery-backup operation. This battery charge cannot be used in parallel grid operation.
SMA Solar Technology AG recommends to set a value between 10 and 30.
9.16 Power Supply of Backup Loads in Parallel Grid
Operation
In parallel grid operation, the backup loads can be supplied from the utility grid as long as the
amperage and voltage of the backup loads' circuits are within the permitted range.
If the current exceeds 20A, a Smart Connected message is sent in any case. If the current exceeds
22A, the contactor between the backup loads and the utility grid is opened after a tripping time
that depends on the level of the current. The contactor is then automatically tested. If the test is
successful, the contactor is closed again and the backup loads can continue to be supplied from the
utility grid.
0 A
20 A
22 A
28 A
48 A
ON
OFF ON
>10 s
ON
OFF ON
OFF ON
Testing
contactor
Notification
Smart
Connected
Contactor
closed
Contactor
open
Tripping
time
>0.005 s
>0.5 s
Figure 22: Behavior of the contactor between the AC backup terminal and the connection to the utility grid at
increased current
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