23 May 2012

Mitsubishi Electric develops all-SiC inverter with power density of 50kVA per liter

Tokyo-based Mitsubishi Electric Corp has developed a prototype forced-air-cooled three-phase 400V output inverter with all-silicon carbide (SiC) power modules that has a power density of 50kVA per liter. The module, which is rated at 1200V/300A, incorporates a SiC MOSFET (metal oxide semiconductor field-effect transistor) and a SiC SBD (Schottky barrier diode). The inverter is expected to contribute to smaller and lighter power-electronics equipment in automotive and industrial applications, among others.

Mitsubishi Electric says that, to increase power density, the electric current density must be increased through lower electric resistance. So, it developed low-resistance wiring by using direct lead bonding to connect power semiconductor chips directly to the main terminals, eliminating the use of conventional high-resistance aluminum lead wires.

To achieve high current density, low-loss (low-resistance) power chips also had to be used, but this required the application of high-speed protection circuits to avoid a large destructive current during short circuits. Mitsubishi Electric applied a SiC MOSFET with a built-in current sensor function to its all-SiC power module and used a high-speed short-circuit-protection circuit, making it possible to use a low-resistance SiC MOSFET even at a high current density. The firm hence achieved a power density of 50kVA per liter via an inverter operation with an output of 156kVA.

The firm says that, while silicon has traditionally been used for power semiconductor devices, in recent years SiC has come to be widely considered as a promising next-generation material. Compared to Si, SiC has a critical electric field for breakdown that is about 10 times higher and enables the reduction of power loss, helping to reduce carbon dioxide emission. Furthermore, the reduction of power loss enables a reduction in cooling equipment, contributing to the overall downsizing and lightening of electronic components for automotive and industrial applications.

Mitsubishi Electric says that it plans to further downsize the inverters for commercial viability.

Tags: Mitsubishi Electric SiC inverter

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