Following a series of vehicle failures on the Yamagata Shinkansen’s new E8 series on June 17 (Tue), 2025, JR East reported on what has been learned from the investigation to date and the immediate response.
Power cut and motor unable to operate
Around 11:24 on June 17 (Tue), a vehicle failure occurred on a downbound outbound train on the Tohoku Shinkansen, which prevented it from running under its own power, and the train stopped for a long time between Utsunomiya Station and Nasushiobara Station. In addition to the train, vehicle failures also occurred on the same day on Tsubasa 136, which was stopped at Oyama Station, a outbound train stopped at Koriyama Station, and Tsubasa 139, which was running between Fukushima Station and Sasakino Station on the Yamagata Shinkansen.
All four of these trains are E8 series rollingstocks that have been in commercial operation since March 2024, and the failures are all in the auxiliary power supply units that supply power to each device. The failure caused the main converter, which drives the motor on the bogie, to no longer receive power, causing the cooling device inside the main converter to stop. As a result, the circuit protection function to prevent overheating was activated, and the motor could not be driven, making the train unable to run.
Direct operation with Tohoku Shinkansen suspended
JR East and the manufacturer conducted an investigation into the four trains and found damage to semiconductor elements inside the six faulty auxiliary power units. The cause of the damage has not yet been identified. Considering that record-breaking heat was recorded in various areas, including central Tokyo on June 17 (Tue), with a maximum temperature of 34.8°C, the cause will be investigated from all perspectives, including environmental factors such as temperature, and necessary measures will be taken.
Currently, due to the suspension of all E8 series independent operations on both the Shinkansen and conventional lines, the Yamagata Shinkansen is providing shuttle service from Fukushima Station with the exception of some direct trains. Transfers are required for trains heading towards Tokyo Station at Fukushima Station, and the number of trains operating between Fukushima Station and Yamagata Station/Shinjo Station is about 80% of normal, and this response will continue until the cause is determined.
