Mitsubishi Electric Corporation (TOKYO: 6503) announced that it has launched a railcar traction inverter system for 1,500V DC catenaries that incorporates the world’s first all-silicon carbide (SiC) power modules made with SiC transistors and SiC diodes. The all-SiC inverter greatly reduces power loss, size and weight compared to conventional insulated gate bipolar transistor (IGBT) power modules and hybrid power modules made with Si transistors and SiC diodes.
Mitsubishi Electric’s large-capacity, all-SiC power modules are expected to help save power as well as lower
the size and weight of equipment used in high power trains including Japan’s Shinkansen.
The new traction inverter system’s switching loss is approximately 55% less than Mitsubishi Electric’s
conventional inverter system incorporating IGBT power modules. The new system also increases
regenerated energy through the use of regenerative brakes in all speed ranges. Thanks to these solutions, total
energy consumption of railcar systems, including their motors, is reduced by about 30% compared to
Size and weight are reduced by about 65% compared to conventional inverter systems with IGBT power
modules and about 30% compared to existing hybrid inverter systems with SiC diodes.
Energy saving in total railway systems is further enhanced by effectively transferring regenerated electric
power from the railcar to stations to be equipped with Station energy-saving inverters (S-EIV).
Main specifications of new traction inverter system
Input voltage: 1,500V DC
Main circuit system: Two-level PWM inverter with regenerative brakes
Control system: Four traction motors with 180kW, parallel control
Cooling system: Self-cooling
The dielectric strength voltage of SiC is about 10 times greater than that of Si. SiC devices can operate at
higher temperatures than Si devices because of the high breakdown voltage and low conduction loss of
thinner semiconductors. Unlike the ongoing development of SiC diodes, development of SiC transistors has
proven difficult due to problems with crystal preparation, which requires highly advanced insulation and
package technologies capable of withstanding high temperatures. Mitsubishi Electric’s R&D and production
units combined their respective expertise in semiconductor development and manufacturing to successfully
develop the new large-capacity, all-SiC power module with MOS-FET for use in the world’s first all-SiC
railcar traction inverter.
Development of SiC power modules has been partially supported by Japan’s New Energy and Industrial
Technology Development Organization (NEDO).
Mitsubishi Electric’s previous record of SiC inverter development
In October 2011, Mitsubishi Electric produced a railcar traction inverter for 600V DC, 750V catenaries
incorporating the world’s first large-capacity hybrid SiC power modules. With help from Tokyo Metro Co.,
Ltd., the system was field-tested in commercial railcars operating on its Ginza Line subway, demonstrating
38.6% energy reduction comparing to conventional inverters in other railcars operating on the same line.