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. This research is featured in the September 2015 issue of the JSAP Bulletin.
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 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.
For a power module in a traction inverter, low power loss, miniaturization, high voltage rating, and high temperature environmental resistance are required.
The Mitsubishi 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.