components, including the sub-floor, which is a compartment located under passenger floor. It's role is to hold equipment box and electrical wires and bolster function parts connecting the car body to the bogie. Affected trainsets were sent back to China progressively between July 2014 and January 2020, before the COVID-19 pandemic. Tender The tender for trains under the contract turnkey 151A was closed in January 2009. The tender results were published in May 2009. Equipment Main propulsion controller The C151A trains are the third commuter type Electric Multiple Unit (EMU) made in Japan to feature electric systems fully manufactured by Fuji Electric. Propulsion is controlled by VVVF Inverter with 2-level IGBT semiconductor controller, rated at 415 kV. Each inverter unit controls two motors on one bogie (1C2M), and one motor car features two of such units. Motors are three-phrase AC induction type, model MLR109, with a maximum output of 140 kW. However, the main difference is that the traction for the trains is higher pitched than the ones from C751B trains which are lower pitched. Bogies The C151A trains use the monolink axle box type bolsterless air spring bogie. There are no major technical differences between a trailer and motor car bogie other than additional electrical components for the latter. Auxiliary systems A break from tradition, the C151A trains features auxiliary inverters for its electrical systems on all six cars of the train. Previously, auxiliary inverters were mounted only on motor cars. The VVVF Inverter is controlled by IGBT semiconductors and rated at 80 kV. A battery charger is built with the inverter and provides 16 kW output. Train formation The configuration of a C151A in revenue service is DT–M1–M2+M2–M1–DT The car numbers of the trains range from x501 to x570, where x depends on the carriage type. Individual cars are assigned a 4 digit serial number. A complete six-car trainset consists of an identical twin set of one driving trailer (DT) and two motor (M) cars permanently coupled together. For example, set 501/502 consists of carriages 3501, 1501, 2501, 2502, 1502 and 3502. The first digit identifies the car number, where the first car has a 3, the second has a 1 & the third has a 2. The second digit is always a 5, part of the identification numbers The third digit and fourth digit are the train identification numbers. A full-length train of 6 cars have 2