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The variable voltage and variable frequency (VVVF) inverter control system has been the mainstream of the traction motor driving system of railcars in Japan. At the initial stage, the VVVF inverter was a two-level inverter employing a gate turn-off thyristor (GTO), but recently a three-level inverter adopting insulated gate bipolar transistor (IGBT) elements has been obtaining the leading position with the view of reducing the size of the equipment and the noise.
Hitachi, Ltd. has developed various kinds of control equipment, which adopt IGBT, for electric cars of Japan Railway Group (JR) ordinary lines as well as for public and private railways. Included among them, there is the equipment to combine the feature of the brake chopper system for utilizing an electric brake effectively on light traffic lines, and the equipment provided with a backup function--which uses a VVVF inverter at the failure of an auxiliary inverter (static inverter, SIV) in a shorter train formation.
The IGBT railcar driving system is an elaborated system designed for: suppressing noise, maintaining a pollution-free environment, energy saving, labor saving, improvement of performance, and improvement of maintainability from the effective management viewpoint. One can say that we have developed a very suitable railcar driving system for the next generation.