Research reported in the Japanese Journal of Applied Physics by researchers at Mitsubishi Electric Corporation describes 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.

Researchers in Japan have developed new power modules comprising all silicon carbide (SiC) MOSFETs (a) and SBDs (b). The power modules show great promise in improving the performance and efficiency of traction inverters for trains, reducing switching losses by 55% compared with conventional inverters.

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.