Researchers at Mitsubishi Electric Corporation describe the development of a new power module made from a SiC MOSFET and a SiC Schottky barrier diode in a train traction inverter. The inverter is used to convert the direct current from the power source to three-phase alternating current suitable for driving the propulsion motors. The results are published in the Japanese Journal of Applied Physics.

Next-generation power electronics capable of reducing energy consumption are in high demand, particularly in the transportation industries. A way of saving energy is to reduce the losses inherent in switching processes and power conversion. Attention is now being given to a compound form of silicon and SiC (silicon carbide) for electronic components, which outperforms 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 developed the new power module for a trial in a train traction inverter low power loss, miniaturisation, high voltage rating, and high temperature environmental resistance are required.

The team prepared the SiC MOSFET for the power module by n-type doping the JFET region. This reduced on-resistance of the device at high temperatures. By combining the SiC MOSFET with a SiC diode (a diode which allows for fast and efficient switching), the team created a power module for a traction inverter rated at 3.3kV / 1,500A. 

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