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Silicon Carbide Ready to Run the Rails

Mitsubishi is showing that silicon carbide electronics can bring big power savings to underground trains

3 min read
Silicon Carbide Ready to Run the Rails
Super Subway: Tokyo's Ginza subway line is part of a trial to test what improvements silicon carbide circuits can make to transportation systems.
Photo: CreativeCommons

If you rode the Ginza Line, Japan’s oldest subway line, in the past year, chances are you took part in the testing of a technology that could drastically boost the efficiency of rail systems. Since February 2012, one of the cars in a six-car train on that line has been equipped with a new kind of inverter, part of a circuit that turns the third rail’s direct current into the alternating current that the train’s motors need. The inverters are made from a material—silicon carbide—that the makers of power electronics are hoping will start a revolution.

Silicon carbide (SiC) has a number of advantages over silicon, among them a wider energy bandgap that enables devices to run at temperatures as high as 600 °C; a breakdown voltage about 10 times that of silicon, making the material robust enough to withstand very high voltages; and high thermal conductivity, allowing it to handle enormous amounts of power. All those properties make SiC especially attractive when engineers must design systems that efficiently convert AC into DC, regulate voltages, and control motors.

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The Transistor at 75

The past, present, and future of the modern world’s most important invention

2 min read
A photo of a birthday cake with 75 written on it.
Lisa Sheehan

Seventy-five years is a long time. It’s so long that most of us don’t remember a time before the transistor, and long enough for many engineers to have devoted entire careers to its use and development. In honor of this most important of technological achievements, this issue’s package of articles explores the transistor’s historical journey and potential future.

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