The traction inverter controls the DC, AC and variable current devices in the vehicle and thus controls and regulates the vehicle's motor. This device is equivalent to the CPU of a computer, and its performance directly affects the performance of the rail transit.
The selection of IGBT module substrates is based on their electrical insulation properties at high voltage, thermal properties (high temperature resistance and good thermal conductivity) and mechanical properties (matching the expansion coefficient of other materials as closely as possible). The commonly used materials are AlN (aluminum nitride) and Al2O3 (aluminum oxide). In this respect, AlN is superior to Al2O3 because of its excellent thermal and mechanical properties. The thermal conductivity of AlN ceramics is generally 180 W/mK, while that of Al2O3 ceramics is 27 W/mK. The thermal conductivity of diamond is extremely high, reaching 1000-2000 W/mK.