JF205C synchronous main alternator is a 3 phase, salient pole type, single shaft extension and self-ventilated machine. It has features of compact structure, high voltage, wide voltage regulation ratio, high speed and high insulation class. The alternator is supported by single bearing. Rotor yoke consists of short shaft, spider and cylindrical yoke. Field pole is integrative in structure and tightened on the yoke with high strengthen bolts. Collecting ring is copper slip ring. The alternator is installed with imported bearing NU326EC4/VA301. Stator segment is made of high quality silicon steel plate DW 360-50 laminations. Stator core is tightened through studs and shrunk on the frame. Stator and rotor are both treated by vacuum pressure impregnation process. There is a centrifugal fan installed on the driving end. This machine has reasonable design in structure and good performance in techinique. It has already been used for 2000 horsepower narrow-gauge diesel electric locomotives exported to Myanmar mad by Sifang Locomotive and Rolling Stock Works. It can also be used for other occasion.