Research reported in the Japanese Journal of Applied Physics by researchers at Mitsubishi Electric Corporationdescribes the development of a new power module made from a SiC metal-oxide-semiconductor field-effect transistor and a SiC Schottky barrier diode. The team successfully trialed the module in a train traction inverter — a device used to convert the direct current from the power source to three-phase alternating current suitable for driving the propulsion motors — with promising results.

Power electronics: Silicon carbide gains traction

Next-generation power electronics capable of reducing energy consumption are in high demand, particularly in the transportation industries. A key way of saving energy in electronics is by reducing the losses inherent in switching processes and power conversion. Much attention is now being given to a compound form of silicon and carbon called silicon carbide (SiC) for electronic components, a material whose properties outperform conventional silicon in terms of thermal conductivity, loss reduction and the ability to withstand high voltages.

Satoshi Yamakawa and co-workers at Mitsubishi Electric Corporation have developed a new power module made from a SiC metal-oxide-semiconductor field-effect transistor (MOSFET) and a SiC Schottky barrier diode (SBD). The team successfully trialed the module in a train traction inverter – a device used to convert the direct current from the power source to three-phase alternating current suitable for driving the propulsion motors — with promising results.

For a power module in a traction inverter, low power loss, miniaturization, high voltage rating, and high temperature environmental resistance are required.

Yamakawa and his team prepared the SiC MOSFET for the power module by n-type doping the junction field-effect transistor region: this reduced on-resistance of the device at high temperatures. By combining the SiC MOSFET with a SiC SBD — a diode which allows for fast and efficient switching — the team created a power module for a traction inverter rated at 3.3kV/1500A.

A new traction inverter system equipped with their power module is stable, highly efficient and reduces switching losses by 55% compared with conventional silicon-based inverters.

Reference and affiliation

Kenji Hamada1, Shiro Hino1,2, Naruhisa Miura1,2, Hiroshi Watanabe1,2, Shuhei Nakata1,2, Eisuke Suekawa3, Yuji Ebiike3, Masayuki Imaizumi3, Isao Umezaki3, and Satoshi Yamakawa1,2. 3.3kV/1500A power modules for the world’s first all-SiC traction inverter. Japanese Journal of Applied Physics 54 04DP07 (2015) http://dx.doi.org/10.7567/JJAP.54.04DP07

1. Advanced Technology R&D Center, Mitsubishi Electric Corporation, Amagasaki, Hyogo 661-8661, Japan

2. R&D Partnership for Future Power Electronics Technology (FUPET), Minato, Tokyo 105-0001, Japan

3. Power Device Works, Mitsubishi Electric Corporation, Fukuoka 819-0192, Japan

This research is featured in the September 2015 issue of the JSAP Bulletin.