19 February 2015

German project to study use of high-frequency SiC power semiconductor switches in industrial applications

Under the project 'Modular Medium-frequency Process Power Supply with Silicon Carbide Power Semiconductor Switches' (MMPSiC), researchers in Germany at the Light Technology Institute (LTI) of Karlsruhe Institute of Technology (KIT), in cooperation with industrial partners TRUMPF Hüttinger GmbH of Freiburg (which makes process power supplies) and Lampertheim-based power semiconductor module maker IXYS Semiconductor GmbH, is studying the feasibility of using high-power silicon carbide switches in power supplies. The aim of the project is to significantly enhance the efficiency of power supplies for industrial processes and hence to reduce energy consumption and CO2 emission.

The three-year project (which started in 2014) has about €800,000 funding from the German Federal Ministry of Research (BMBF) under the programs 'Information and Communication Technology 2020' (IKT 2020) and 'Power Electronics for Increasing Energy Efficiency' (LES 2). The LTI is receiving €439,000. Total project funding amounts to €1.3m.

In float-zone melting processes for producing highly pure crystalline materials such as silicon, the basic material is molten electrically within a very small zone. By moving the melting zone, the material crystallizes more purely. For example, this process is used for the production of highly pure monocrystalline silicon for solar cells.
Up to now, the power supplies of float-zone systems have been tube-based amplifiers with a maximum electrical efficiency of 65%.

However, these could be replaced by power semiconductors made of silicon carbide. Due to silicon carbide's wider electronic bandgap, much higher operating temperatures can be reached compared to conventional semiconductors. SiC-based power electronics is therefore characterized by an enhanced energy efficiency and compactness.

The efficiency of power supplies could be increased to well over 80%, it is reckoned, significantly reducing power consumption and greenhouse-gas emissions. For example, a single large-scale float-zone reactor, consisting of twenty 50kW process power supplies with an annual operating time of 4800 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).

"Power supply of energy-intensive industrial applications, such as a float-zone process, requires switching at high frequencies," explains project manager Dr Rainer Kling of LTI. "Silicon carbide has not yet been tested at these high frequencies," he adds. Apart from long-term stability tests, the KIT researchers involved in the MMPSiC project are therefore studying the control and layout of the circuitry.

Tags: Power electronics SiC

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