This time, my travel mainly revolved around the latest Osaka Metro topics, for example, Yumeshima Station, 400 Series, and "e METRO MOBILITY TOWN." However, I also took the time to capture videos of the Tanimachi Line's 22 series and the Yotsubashi Line's 23 series trains installing variable frequency drive with Hitachi gate turn-off thyristor (GTO) technology, which are gradually becoming less common due to equipment updates or 30000A Series' transferring from Chuo Line after EXPO 2025.
The new 20 series trains, which were sometimes regarded as a symbol of the 1990s and 2000s, the first Heisei period in Japan, for the Osaka Municipal Subway, were deployed across various lines, utilising the third rail for electric collection.
Recently, however, 21 Series on the Midosuji Line and 25 Series on the Sennichimae Line have undergone equipment updates, leading to their discontinuation by 2021. Meanwhile, 24 Series on the Chuo Line has been moved to the Tanimachi Line and renumbered to 22 Series, effectively disappearing from service. These days, only the Tanimachi Line's 22 series and the Yotsubashi Line's 23 series remain. However, all unrefurbished carriages of the 23 series had already been taken out of service by April 2025. All sets must be upgraded, replacing Hitachi GTO technology with a newer drive.
The sound of the variable frequency drive with Hitachi GTO was a significant factor in my becoming a railfan, so I wanted to see it and listen to its sound while I still could. Having encountered the unrefurbished 22 Series and 23 Series during this trip, I now feel a sense of closure and no regrets.