Rail traction
Electric trains and metros on overhead wires, and diesel-electric locomotives.
Conversion and use · Transport systems · No. 113
- Conversion and use
An electric train turns about 80% of its wire power into motion and hands some back every time it brakes.
Chart: Illustration: Rail traction
Where it comes from
Chart: Map of where it comes from
A pantograph slides along a 25,000-volt wire; a transformer and fast transistor switches feed the axle motors. Reversed, the motors brake the train and return about 10-30% of traction energy.
Three things to know
- The Americas have only 0.5% of rail route-km electrified, against 56.8% in Europe and 62.8% in Asia Pacific.
- A diesel-electric locomotive delivers only about 29% of its fuel energy as useful work, a third of an electric train's figure.
- Electric trains cost over 35% less to run than diesel, but wires only pay off on busy lines.
The journey
- 1 Contact wirePantograph collects 25 kV AC or DC
- 2 TransformerSteps line voltage down, about 94% efficient
- 3 ConverterIGBTs make variable-frequency three-phase power
- 4 Traction motorsAxle motors and gearboxes turn wheels
- 5 BrakingMotors regenerate power back to the line