AC traction in Finland

Both British Rail and London Underground are looking at the potential of AC inverter-driven induction-motor drives for railway traction, as part of their modernisation programmes. Such systems have been used in Finland for many years, and Helsinki Metro is the only metro outside Japan to use only AC drives. The authors discusses the power apparatus of the Helsinki Metro. This includes 125 kW continuously rated squirrel-cage induction motors, voltage source PWM inverters, and rheostatic braking. The author discusses the operation and maintenance of the metro rail cars.<
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