AEG 8000012364 BAL operating instructions Principle of Operation of the INV, Electrical

"UniVert 2" inverter

Figure 2 illustrates the principle of an INV.

In normal operation, the load is supplied "Online" by the INV. With systems comprising several parallel INVs, the load current is divided in accordance with the number of INVs. Depending on the system design, a power supply using up to 8 INVs can be realised. In addition to the parallel operation of several INVs, the reliability of supply can be further increased by integrating a static bypass switch, SBS. In the event of a failure of several INVs, switchover to the mains takes place without any interruption. Apart from power cabling, a bus line is required for control purposes between the units for systems comprising several INVs (and SBSs). The bus line has to be terminated at both ends with a resistor.

ATTENTION:

This INV must not be connected in parallel to the mains on the output side!

2.4Principle of Operation of the INV, Electrical

After connection of the DC voltage, the DC filter capacitors are charged via the softstart device. The control unit activates a bridging contactor as soon as the capacitor charging process is finished. The DOU displays measured values (output voltage/output current) on the LCD and the unit status via LEDs. The INV is switched on using the ON/OFF switch on the DOU. When the INV has been switched on, it can be started or stopped by connecting or disconnecting the

DC voltage supply.

The transistor INV set, pulsed with approx. 20 kHz, transforms the direct voltage into a single-phase sinusoidal AC voltage. The voltage is transformed electrically isolated to the required AC output voltage using a transformer. The secondary voltage is led to the load terminals via the AC filter, a miniature circuit-breaker, a current transformer and the INV output contactor. The stabilised output voltage of the INV is short-circuit-proof and can supply loads from capacitive through ohmic to inductive, as well a non-linear loads with a high crest factor. The INV also supplies high starting currents for motor loads. Refer to chapter "Technical data" for the exact specifications. The entire control and monitoring process is carried out using a microprocessor. LEDs and relays show the unit status, whilst output voltage and output current are displayed on an LCD. INVs for parallel operation need a choke between the INV output and the busbar. When several INVs are operated in parallel, or one or more INVs are operated with an SBS, a CAN bus is required between the units for control purposes. An additional CAN bus allows the unit to be integrated in a power supply system and connected to a central control and monitoring unit (PSM).

With individual units, the INV immediately starts after actuating the ON/OFF switch. With an INV with SBS and presence of the mains, the INV starts immediately, but the output contactor is only switched on after synchronisation with the mains. With systems comprising several INVs, these synchronise to the mains and then jointly switch on the output contactor. The INV can be switched off in every operating status without delay using the ON/OFF switch.

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