AEG 8000012364 BAL Function of the System, Individual INV operation, Parallel INV operation

"UniVert 2" inverter

Individual INV operation:

Here an INV is supplied with DC and itself supplies the AC load. In the event of INV fault or switch-off, the load is no longer supplied.

Parallel INV operation:

In order to increase redundancy or performance, up to 8 INVs of the same type and the same output can be connected in parallel. Note that if one or several of the INVs fail, the remaining INVs take over the load. Overload of the remaining INVs can be prevented by choosing the right number of redundant INVs. If the number of INVs that fail or are switched off exceeds the number of available redundant INVs, the remaining INVs switch off together.

When the INVs are switched back on by connecting the DC, they do not switch on their output contactors at the same time until a sufficient number of INVs (in accordance with the redundancy setting) are available to take over the load.

INVs for parallel operation need a choke between INV output and busbar.

Individual or parallel operation with SBS:

If one or more INVs are combined with an SPS, switchover of the loads from the mains to the INV and vice versa is possible without any interruption. With parallel operation systems, the load is distributed to the remaining INVs if one or several INVs fail. The system may switch over to the mains when a voltage drop occurs on the load busbar as a result of the failure of one INV, or if the number of INVs still operating is insufficient (redundancy setting). In order to switch the load back from the mains to the INVs, n-R INVs must be in operation (where R = redundant INVs).

2.2Function of the System

Individual INV operation:

The INV as an individual unit supplies the loads. If it is switched off or disturbed, either by internal faults of the INV or by failure of the

DC supply or by a DC voltage deviation, the AC loads are no longer supplied. The INV is not synchronised with the mains or other

AC voltage sources. The INV can be connected to the DC voltage using a switching device on the input (miniature circuit-breaker, contactor). An internal softstart device limits the current to values below the rated current. If the INV is switched to the DC, the control unit starts operating. The INV supplies the output voltage if the unit is additionally switched on using the ON/OFF switch. If the supplying mains fails, the battery of the power supply system is discharged (also) by the INV. When the DC undervoltage monitoring value is reached, the INV is switched off. If the battery is charged after the mains voltage has returned, the INV is automatically started when a limit value of the DC undervoltage monitoring is exceeded.

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