AEG 8000012364 BAL User Manual

Page of 42
"UniVert 2" inverter 
 
Page 14 of 42 
8000012364 BAL, en 
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!
 
 
2.4 
Principle 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.