Operating principle of the SMA Backup

Various SMA Backup operating modes

Procedure in the event of a grid failure

In the event of a grid failure, the loads are disconnected from the utility grid for the time defined in the parameter Operation.BckSwOnDl (Minimum duration of grid fault for start of automatic backup operation). After the defined time, the loads on line conductors L1, L2, and L3 are supplied via the inverter's battery-backup operation. To avoid phase jumps on the load side, SMA Solar Technology AG recommends an appropriate switchover time. You can set this time via the parameter Operation.BckSwOnDl (Minimum duration of grid fault for start of automatic backup operation).

Return of the utility grid

During power outages or grid maintenance, the utility grid is typically switched on and off several times. The waiting time set in the parameter Operation.BckSwOffDl (Minimum duration of grid recovery for deactivation of backup operation) ensures that the system only switches back to parallel grid operation once the grid condition is truly stable. However, during this time, the loads continue to be supplied with battery backup power via the inverter. To prevent phase jumps when switching back to the utility grid, the loads are switched off again for the duration defined in parameter Operation.BckCbSwDl (Interruption of load supply during the transition from automatic backup to feed-in operation). After this period, the loads are again supplied via the utility grid.