Basic principles of online and offlineUPS
The example of
shows the inverter section as a three-phase two-level
inverter. This is the common topology of most of the UPS systems from 60kVA to
>500kVA. Nevertheless, as described in the previous chapters, here too, three-level
circuits can be utilised. In the simplest case, diodes or thyristors can be used for a
rectifier in 6-pulse or 12-pulse configuration. Also, the previously described Vienna
Example of a three-phase two-level transformer-based and transformer-less
In addition to the standard single- and three-phase UPS systems, there are other UPS
topologies. These include the so-called power qualityUPS or delta conversion systems.
These converters control current, voltage and power factor, and independent of the
input parameters the output parameters are kept stable. These systems are required in
sensitive industrial processes, such as the semiconductor industry.