Why do some trains have overhead lines?

An overhead line or overhead wire is an electrical cable that is used to transmit electrical energy to electric locomotives, trolleybuses or trams.

What is the difference between overhead system and third rail system?

As a solid composite rail running along the track, a third rail is more rugged than an overhead contact wire and has a longer life expectancy. A study performed for Dubai Metro found that a 1.5kV dc third rail traction system can also cost up to 13\% less than a 750V dc third rail system.

Do trains have overhead lines?

Trains are powered by electricity carried through overhead lines or a conductor rail, sometimes called the third rail. Overhead lines are much more dangerous and carry 25,000 volts – that’s 100 times greater than the power supply in your home.

Why do trains use DC power?

DC motors are used on trains is because of their high torque and good speed control. Compared to AC motors, DC motors can provide industry applications with a fine balance of strong starting torque and controllable speed for seamless yet precise performance.

Why is third rail used?

Third-rail systems are a means of providing electric traction power to trains using an additional rail (called a “conductor rail”) for the purpose. The running rails are electrically connected using wire bonds or other devices, to minimise resistance in the electric circuit.

What is third rail in metro?

Third Rail system is the modern technology wherein the power supply line is placed in between the two track of the rail, and the train gets the seamless power supply as it runs on the tracks, where as the AC traction system supplies the power through an overhead line running along the track.

How is third rail powered?

Third rail systems are always supplied from direct current electricity. Trains have metal contact blocks (‘contact shoes’) which make contact with the conductor rail.

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