Silicon Carbide Components Enable Highly Compact UPS Inverter Efficiency of 98.7%

Researchers at the Fraunhofer Institute for Solar Energy Systems ISE (Freiburg, Germany) have developed a highly compact and efficient inverter for use in uninterruptible power supplies (UPS) for electrical devices.

The demonstrator, which contains innovative silicon carbide components, was developed in cooperation with an industry partner and achieved an efficiency of 98.7 percent. The research and development findings can be applied to other areas of electronic power conversion, e. g. electric mobility or portable power supply, ISE reports in a press release.

Efficiency plays a very important role

UPS inverters ensure that electrical devices continue to be supplied with power during disruptions to the power grid. In combination with a battery, they allow electrical power outages of varying lengths to be bypassed. For particularly critical loads, such as computer centers, online UPSs offer the highest protection as they are connected between the grid and the load.

This does mean, however, that all energy is transferred via the UPS inverter even during periods of disruption-free operation. Efficiency therefore plays a very important role for this application, as it is closely connected with the costs required to operate the UPS. This context provided the starting point for the Fraunhofer ISE project, which has now been successfully completed.

Compact and highly efficient in one

Using silicon carbide (SiC) transistors, scientists were able to showcase a UPS inverter with an output of 10 kW and a volume of just five liters. Despite its highly compact design, the inverter still achieved a very high efficiency of 98.7 percent. The good dynamic and static properties of the SiC transistors, such as on-state resistance and switching loss, permit a switching frequency of 100 kHz.

Lower costs thanks to higher efficiency

"On the whole, this design saves system-related costs and materials. In comparison to using a conventional clock rate of 16 kHz, we were able to reduce the size and price of the main inductance in our UPS inverter by around two thirds," says development engineer Cornelius Armbruster.

For applications in online UPS systems, efficiency is even more important than reducing materials, as it not only compensates short-term voltage dips in the grid, but also ensures that electrical devices are continuously supplied with power via the UPS.

Silicon carbide: a material with prospects

For many years, the Fraunhofer Institute for Solar Energy Systems ISE has been researching and developing highly efficient power electronics for renewable energy systems and the application of the latest components made from gallium nitride and silicon carbide.

The technology demonstrator showcased by Fraunhofer ISE, which was commissioned by ROHM Semiconductor, once again highlights the potential of these semiconductor materials.

The SiC transistors used in the demonstrator were provided by ROHM Semiconductor. Thanks to this semiconductor material, transistors will be available for even higher currents in the future, allowing systems to achieve considerably higher output powers.