Researchers of the Light Technology Institute (LTI) of Karlsruhe Institute of Technology (KIT), in cooperation with their industrial partners TRUMPF Hüttinger and IXYS Semiconductor, study the use of high power silicon carbide semiconductor switches. The project is funded by the German Federal Ministry of Research with 800,000 euros.

From the production of semiconductor to coating of displays to processes in automobile manufacturing: Many industrial processes consume large amounts of electrical energy. Among them are also processes playing an important role for the transformation of the German energy system, such as floating zone melting processes to produce highly pure crystalline materials like silicon. By this process, the basic material is molten electrically within a very small zone. By moving the melting zone, the material crystallizes purer than before. Amongst others, this is used for the production of highly pure monocrystalline silicon for solar cells.

So far, power supplies of floating zone systems are tube-based amplifiers with a maximum electrical efficiency of 65%. If they were replaced by power semiconductors made of silicon carbide, efficiency of power supplies would be increased to well over 80%. So, power consumption and greenhouse gas emissions would be reduced significantly. For example, a single large-scale floating zone reactor, consisting of twenty 50kW process power supplies with an annual operating time of 4,800 hours, would lead to a reduction of electrical energy by more than 200,000kWh and produce 109 tons of CO2 less (Federal Environmental Agency Germany, July 2013).

Feasibility of such power supplies is studied by researchers of the Light Technology Institute (LTI) of KIT in cooperation with the industry partners TRUMPF Hüttinger GmbH + Co. KG (Freiburg) and IXYS Semiconductor GmbH (Lampertheim) under the cooperation project “Modular Medium-frequency Process Power Supply with Silicon Carbide Power Semiconductor Switches” (MMPSiC). Silicon carbide has several advantages: Thanks to the wider electronic band gap, significantly higher operating temperatures can be reached compared to conventional semiconductors. Power electronics based on silicon carbide is characterized by an enhanced energy efficiency and compactness.

“Power supply of energy-intensive industrial applications, such as a floating zone process, requires switching at high frequencies,” explains project manager Dr. Rainer Kling, LTI. “Silicon carbide has not yet been tested at these high frequencies. Here, we are entering new territory.” Apart from long-term stability tests, the KIT researchers involved in the MMPSiC project study the control and layout of the circuitry.

The MMPSiC project is funded by the Federal Ministry of Education and Research (BMBF) with about 800,000 euros under the programs Information and Communication Technology 2020 (IKT 2020) and Power Electronics for Increasing Energy Efficiency (LES 2). The LTI of KIT receives a substantial amount of about 439,000 euros. The total project volume amounts to 1.3 million euros. The cooperation project started in 2014 and has a duration of three years.