Japanese subway trains will soon start to test a new generation of traction inverters that incorporate high-capacity silicon carbide (SiC) power modules, claimed to cut energy consumption by 30%, as well as needing less maintenance and emitting less noise than conventional silicon (Si) power modules.

Compared to Si-based power modules used in current traction inverters, the SiC power modules, developed by Mitsubishi Electric, offer several improvements. As well as cutting power losses by about 30%, the inverters said to be about 40% lighter and smaller than conventional designs. They also improve the performance of regenerative braking systems, allowing them to produce more electricity.

The new inverters incorporate two 1.7kV and 1.2kA SiC chips. Their high-frequency switching capabilities are said to result in a 40% reduction in motor power losses. They will also cut noise levels by up to 6dB compared to conventional models.

Silicon carbide devices can operate at higher temperatures and with lower switching losses than traditional silicon components. Semiconductor and inverter developers around the world have been working on SiC technologies for many years, but the devices are still more expensive than traditional silicon systems.

Following a series of field tests starting January 2012, the first commercial application for Mitsubishi’s new SiC inverter modules is expected to be in subway trains operated by Tokyo Metro.