Mitsubishi HVIGBT X Series: Powering Rail Transit Traction Systems
Mitsubishi Electric has been a pioneer in rail transit power semiconductors for decades, and its X Series HVIGBT modules represent the state of the art for traction converter applications. Covering voltage ratings from 1700V to 6500V and current ratings from 600A to 2400A, these modules are the core power switching components in both high-speed rail and urban metro traction systems worldwide.
X Series HVIGBT Technical Architecture
The X Series HVIGBT incorporates Mitsubishi Electric’s 7th generation CSTBT (III) chip technology (Carrier Stored Trench-Gate Bipolar Transistor), which significantly reduces both conduction and switching losses compared to previous generations. The freewheeling diodes utilize RFC (Relaxed Field of Cathode) structure for optimized reverse recovery performance. High-temperature solder is used for chip bonding, and improved metallized ceramic substrates and gel materials enhance long-term reliability.
Surface Charge Control Technology
A defining feature of the X Series is the Surface Charge Control (SCC) technology, which provides exceptional humidity robustness. Even under condensation conditions, the HVIGBT modules maintain excellent blocking voltage characteristics. This is critical for rail transit applications where traction converters may be exposed to wide-ranging environmental conditions including humidity, temperature cycling, and vibration.
Power Cycling Capability for Transit Duty
Rail transit applications impose severe power cycling demands on HVIGBT modules. In high-speed rail applications, traction transformers convert 25kV AC to lower voltage, which is rectified to DC and then inverted to three-phase AC for asynchronous motors. In urban metro systems with DC1500V traction, the shorter inter-station distances require frequent start-stop cycles, creating more severe junction temperature and case temperature fluctuations. The X Series achieves 2.7 times better power cycling capability compared to the previous H Series (for 3.3kV modules), significantly extending traction converter service life.
SiC Innovation in Rail Traction
Mitsubishi Electric commercialized the world’s first 3.3kV full-SiC power module for rail transit in 2013. The FMF750DC-66A module achieved 61% reduction in turn-on energy and 95% reduction in turn-off energy compared to silicon IGBT equivalents. The latest Unifull series SBD-embedded SiC modules, using LV100 packaging with 3.3kV/200-800A ratings, reduce chip area by 54% and switching losses by 58% while completely eliminating bipolar degradation risk. These modules have been in mass production since 2023 and are already deployed in global HVDC transmission and rail transit systems.
Comprehensive Voltage Range for All Transit Systems
The X Series standard type covers 1700V to 6500V at 600A to 2400A for main traction converters, while the dual type covers 1700V to 4500V at 450A to 1200A for auxiliary converters. All modules operate at junction temperatures from -50C to 150C with generous safe operating area margins. The series maintains package compatibility with existing H Series and R Series HVIGBT, enabling straightforward upgrade paths for existing rail transit platforms without mechanical redesign.
