GBT (Insulated Gate Bipolar Transistor) modules with a 34mm package size are power electronic devices used for high-voltage and high-current applications. IGBT modules combine the features of both MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) and bipolar junction transistors, providing advantages such as high voltage capability, low on-state losses, and fast switching speeds. The 34mm package size refers to the physical dimensions of the module.