Trend of railway technologies and power semiconductor devices

Transportation has a big share of energy consumption, especially automobiles. Railway saves energy in the field of mass freight transportation, commuter services and high-speed medium distance passenger transportation. Shifting transportation media from trucks and automobiles to railways is important for future energy and environmental issues. It is necessary to have high railway productivity to win the competition between transportation media. With regard to high-speed passenger transport, electric multiple units are more advantageous than locomotive hauled trains, and double-deckers have 30% greater productivity than ordinary railway vehicles. Inverters have made great progress due to power semiconductor development. The smaller power convertor offers more passenger room and greater productivity. On-board convertors can be much smaller if we use 3.3 kV and 4.5 kV IGBTs and two level convertors instead of three level ones. Smaller losses and smaller harmonics are expected for these convertors to enable self-cooling and avoid extra measures to satisfy EMC requirements. If 10-40 kV power semiconductors are made, we have the prospect of realizing transformerless railway vehicles for 25 kV AC systems by adding the role of a main transformer of traction circuit to convertors. In addition, electric vehicles with accumulators, hybrid vehicles using both engine and accumulator and cars with fuel cells are discussed for future environment friendly automobiles. Electric traction seems unavoidable for future automobiles, which means a huge market for power convertors and power semiconductor devices in the 21st century.