Electric Locomotive

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electric locomotive

[i¦lek·trik ‚lō·kə′mōd·iv]
(mechanical engineering)
A locomotive operated by electric power picked up from a system of continuous overhead wires, or, sometimes, from a third rail mounted alongside the track.

Electric Locomotive

 

a locomotive driven by traction motors that may receive their power from a contact system or, less often, from both a contact system and storage batteries that are mounted in the locomotive. In the latter case, the locomotive may be termed a contact-storage-battery locomotive. Other electric locomotives are powered by storage batteries alone and are called storage-battery locomotives.

According to the type of duty performed, electric locomotives may be classified as switching, industrial, mining, and main-line locomotives. Main-line locomotives may haul freight, passengers, or both. Electric locomotives may use direct current, alternating current, or a combination of the two. In order to increase hauling capacity and to improve the turnaround cycle, several electric locomotives controlled from one cab may be used at one time.

The first Soviet main-line electric locomotive was built jointly in 1932 by the Kolomna Plant and the Dinamo Moscow Plant. The main-line electric locomotives now operating in the USSR use either direct current at a voltage of three kilovolts (kV) or 25-kV single-phase alternating current at the commercial frequency of 50 hertz (Hz). When sections of track have both current systems, combination locomotives are sometimes used.

In addition to the current systems mentioned above, electric locomotives abroad use older systems, such as 1.5-kV direct current or single-phase alternating current at a voltage of 11–16 kV, the frequencies employed being 16 2/3 Hz and 25 Hz. For straight-through express service in Western European countries that have differing current systems (such countries include France, Belgium, and the Federal Republic of Germany), passenger locomotives use one of four supply systems: 1.5-kV direct current, 3-kV direct current, 25-kV single-phase alternating current at 50 Hz, and 15-kV alternating current at 16 2/3 Hz.

An electric locomotive consists of mechanical components and electrical and pneumatic equipment. The mechanical components include the body (in which most of the equipment is located), the running gear, and the automatic coupling. The locomotive’s all-metal body usually rests on two- or three-axle trucks, which consist of welded, cast, or bar frames that are made of steel and in which the wheel pairs and journal boxes are mounted. The trucks have spring suspension, a brake lever gear, and traction drive.

The locomotive’s traction motors are mounted on the trucks. In electric freight locomotives a system of axle-hung traction motors is used that features very simple gearing and that increases the action of the wheel pairs on the track. High-speed electric locomotives, including those designed to pull freight trains at speeds of up to 120 km/hr or more, use the nose-suspension drive, which lessens the action of the wheel pairs on the track by supporting the traction motors on the truck’s cushioned frame. In this case, torque is transmitted to the axle of a wheel pair through gearing that is more complicated than that used in the axle-hung motor system. Torque is sometimes transmitted from a high-power traction motor to two or three wheel pairs rather than to one only.

The electrical equipment of an electric locomotive includes traction motors (generally DC), voltage converters for powering auxiliary low-voltage devices, starting and control assemblies, safety apparatus, current collectors, and auxiliary machines, such as compressor motors. AC locomotives also have a main transformer and rectifiers for supplying power to the traction motors.

The pneumatic equipment of an electric locomotive includes a compressor, compressed-air reservoirs, and the braking equipment. Compressed air is used to power the actuators of the train’s control and braking systems.

The speed of an electric locomotive is regulated by varying the voltage at the traction motors and by altering their magnetic flux. When a DC locomotive begins to move, all the electric motors function in series. As the speed increases, they shift into series-parallel operation and, later, into parallel operation. In each case, the motor’s circuit is connected to a starting rheostat whose initial, maximum resistance is gradually removed for a smooth speed increase.

In an AC locomotive, voltage is controlled either on the low-voltage side of its transformer or on the high-voltage side. In the system that controls voltage on the low side—the most commonly used system in Soviet electric locomotives—the voltage is regulated by varying the number of turns of the secondary winding of the step-down power transformer. In the system for controlling voltage on the high side—the principal system used abroad and in the ChS electric-locomotive series—the number of turns of the primary winding is varied. Most of the locomotives in service are equipped with devices for either rheostatic or regenerative electric braking.

The basic specifications of the main-line electric locomotives most commonly used in the USSR are presented in Table 1.

The VL10 and VL8 series and some VL22M electric locomotives are equipped with regenerative-braking systems. In the other series, the superscript “T” indicates that the locomotive uses rheostatic braking, the superscript “R” indicates that it uses regenerative braking, and the superscript “K” indicates that it is equipped with silicon rectifiers.

The VL80 locomotive is the most powerful electric freight locomotive in the world, and the ChS4T and ChS4 are the most powerful electric passenger locomotives. The locomotives of the VL (Vladimir Lenin) series are built in the USSR, and those of the ChS series are built in plants of the Czechoslovak Socialist Republic.

The ChS200 eight-axle electric passenger locomotive, which produces 8,400 kW of power and has a maximum operating speed of 200 km/hr, was tested in the USSR in 1977. In 1978, tests were conducted of eight-axle single-phase high-power AC freight locomotives. The locomotives had asynchronous and commutatorless traction motors that used thyristor converters to regulate speed.

REFERENCES

Bystritskii, Kh. Ia., Z. M. Dubrovskii, and B. N. Rebrik. Ustroistvo i rabota elektrovozov peremennogo toka. Moscow, 1973.
Ustroistvo i remont elektrovozov postoiannogo toka. Moscow, 1977.
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