The feature of transistor high frequency carbon steel welder includes five parts- (1) Low voltage transformer device: The voltage of three phase transformer system is low and stable. This transformer is more secure than high voltage type's. (2) D.C power supply cabinet: The D.C power supply is adapted low voltage circuit system and semiconductor technology. (3) High frequency oscillator output cabinet: This device is constituted by a parallel with MOSFET power module. Each single module is carrying 50kw, operational frequency is 250Khz ~ 400Khz. (4) Distilled water cooling circulation system: This system is adopted the plat pattern of the heat exchanger to reduce the heat and maintain the welding machine at a safe working temperature range. (5) PLC control system console: This control system can quickly display fault diagnosis for rapid and effective maintenance.