SMA SI 3.0-11 Installation - Manual (Page 29)

SMA Solar Technology AG 7 Electrical Connection
Installation Manual SI30M-44M-60H-80H-IA-en-30 29
7.4.3 Connecting an Automatic Transfer Switch in the Battery Backup
System
7.4.3.1 Automatic Transfer Switch Function
The automatic transfer switch separates the utility grid from the battery backup grid in battery backup systems. The control
cable, measuring cable and power cable link the automatic transfer switch to the Sunny Island (for circuitry overview,
see the Quick Reference Guide "SMA Flexible Storage System with Battery Backup Function").
7.4.3.2 Connecting the AC Power Cables to the Automatic Transfer Switch
The AC power cables conduct the energy between the battery backup grid and the Sunny Island (for circuitry
overview, see the Quick Reference Guide "SMA Flexible Storage System with Battery Backup Function").
Requirements:
☐ For a three-phase battery backup system, L1 must be assigned to the master, L2 to slave 1, and L3 to slave 2.
This creates a right-hand rotating magnetic field.
☐ The power of the AC sources in the battery backup grid must not exceed the maximum connected power of the PV
inverters in the battery backup systems (see Section 10.2 "AC2 Connection for Utility Grid and Generator (External
Energy Source)", page 95). The powers of the individual Sunny Island inverters are added to yield the total
maximum power.
Cable requirements:
☐ Copper wire
☐ Number of conductors in the cable: 3
☐ Conductor cross-section: 10 mm² to 16 mm²
☐ Cable diameter: 9 mm to 18 mm
Procedure:
• On the Sunny Island, connect the power cable from X3 to terminal
AC2 Gen/Grid (for circuitry overview, see the Quick Reference
Guide
"SMA Flexible Storage System with Battery Backup Function").
Ensure that the cable is correctly connected (see Section 7.5.2
"Connecting the AC Power Cable", page 52).
• Connect the line conductor to AC2 Gen/Grid L.
• Connect the neutral conductor to AC2 Gen/Grid N
TT
.
• Connect the grounding conductor to AC2 Gen/Grid PE.
7.4.3.3 Connecting the Control Cables to the Automatic Transfer Switch
The control cables conduct the control signals of the multifunction relays to the contactors (for circuitry
overview, see the Quick Reference Guide "SMA Flexible Storage System with Battery Backup Function").
Procedure:
1. On the master, connect the cable from X5 L and X5 N (for the
control voltage) to terminal AC1 Loads/SunnyBoys. Ensure that
the cable is correctly connected (see Section 7.5.2 "Connecting
the AC Power Cable", page 52).