with the implementation of direct operation with the Gwacheon and Ansan lines, chopper control trains were transferred to Seoul Subway Line 3 and introduced in vacant positions. At the time of introduction, 17 direct current-only 10-car formations, 3 direct-current combined 10-car formations, and 52 additional cars according to 10-car 456-463 formation were produced and introduced at Daewoo Heavy Industries' Uiwang Plant. 17 direct current 10-car formations (410-426 formation) and 10-car 10-car 3 formations (469-471 formation) for both direct current were produced in 1994, and 52 by-cars were introduced from 1994 to 1995 . As part of the 456~463 10-car system, 12 cars were incorporated into the 456~463 and 40 cars as the 464~468. Third introduction (2020) Combination of direct current (DC AC): 481 to 485 formation Producer: Hyundai Rotem As an electric train introduced with the opening of the Jinjeop Line, 5 trains of 10 cars for both direct current were manufactured and introduced by Hyundai Rotem. The specifications are similar to the 4th introduction of the VVVF train of the 2000th unit of the Seoul Transportation Corporation. However, the electrical components are different from those of the 4th train of Line 2, and the propulsion control device is 312x04~15 trains of the 311000 train group, 319x08~10 trains of the 319000 train trains of the Korea Railroad Corporation, 341x31~55 trains of the Korail Class 341000 trains of the Korea Railroad Corporation, It is the same driving sound as the 351x44~60 and 35179 trains of the 351000 unit of the Korea Railroad Corporation. In addition, despite being modelled in 2020, automatic doors are installed in all aisles, as are the 2nd train of Seoul Transportation Corporation No. 2000 VVVF train and the 1st train of Seoul Transportation Corporation No. 3000 VVVF train. Fourth introduction This is another electric train made to replace old vehicles for the first and second cars introduced in the 1990s. The propulsion control device adopted an inverter developed by Dawonsys based on the IGBT device of Hitachi, Japan. Status The 401~415, 417~424, and 426 formations only between Jinjeop and Namtaeryeong, and the 451~460, 462, 464, 466, 468, 470~471, and 481~485 formations run on the Gwacheon Line and Ansan Line. It is a cross-current combined vehicle that runs directly through the section. Intermediate Bypass Composition Changes Along with the detailed safety diagnosis, the composition of the intermediate vehicle was partially changed. 414 formation: No. 4814 → No. 4816