Electric transmission or electric powerchain is a

transmission system :''See Transmission (mechanics) for a car's transmission system'' In telecommunications, a transmission system is a system that transmits a signal from one place to another. The signal can be an electrical, optical or radio signal. Some transmissi ...

for propelling

motor vehicles A motor vehicle, also known as motorized vehicle or automotive vehicle, is a self-propelled land vehicle, commonly wheeled, that does not operate on Track (rail transport), rails (such as trains or trams) and is used for the transportation of pe ...

. It is used for a variety of applications in

road A road is a linear way for the conveyance of traffic that mostly has an improved surface for use by vehicles (motorized and non-motorized) and pedestrians. Unlike streets, the main function of roads is transportation. There are many types of ...

rail Rail or rails may refer to: Rail transport *Rail transport and related matters *Rail (rail transport) or railway lines, the running surface of a railway Arts and media Film * ''Rails'' (film), a 1929 Italian film by Mario Camerini * ''Rail'' ( ...

, and marine

transport Transport (in British English), or transportation (in American English), is the intentional movement of humans, animals, and goods from one location to another. Modes of transport include air, land (rail and road), water, cable, pipeline, an ...

. The defining characteristic of electric transmission is that it avoids the need for a

gearbox Propulsion transmission is the mode of transmitting and controlling propulsion power of a machine. The term ''transmission'' properly refers to the whole drivetrain, including clutch, gearbox, prop shaft (for rear-wheel drive vehicles), differe ...

, by converting the

mechanical force In physical sciences, mechanical energy is the sum of potential energy and kinetic energy. The principle of conservation of mechanical energy states that if an isolated system is subject only to conservative forces, then the mechanical energy is ...

of the

engine An engine or motor is a machine designed to convert one or more forms of energy into mechanical energy. Available energy sources include potential energy (e.g. energy of the Earth's gravitational field as exploited in hydroelectric power gen ...

into

electrical energy Electrical energy is energy related to forces on electrically charged particles and the movement of electrically charged particles (often electrons in wires, but not always). This energy is supplied by the combination of electric current and electr ...

(through a

dynamo file:DynamoElectricMachinesEndViewPartlySection USP284110.png, "Dynamo Electric Machine" (end view, partly section, ) A dynamo is an electrical generator that creates direct current using a commutator (electric), commutator. Dynamos were the f ...

alternator An alternator is an electrical generator that converts mechanical energy to electrical energy in the form of alternating current. For reasons of cost and simplicity, most alternators use a rotating magnetic field with a stationary armature.Go ...

), and using the electrical energy to drive

traction motors A traction motor is an electric motor used for propulsion of a vehicle, such as locomotives, electric or hydrogen vehicles, elevators or electric multiple unit. Traction motors are used in electrically powered rail vehicles ( electric multiple ...

, which propel the vehicle mechanically. The traction motors may be driven directly, or in some cases, via a

rechargeable battery A rechargeable battery, storage battery, or secondary cell (formally a type of Accumulator (energy), energy accumulator), is a type of electrical battery which can be charged, discharged into a load, and recharged many times, as opposed to ...

; if rechargeable batteries are used, the vehicle is considered to be a

hybrid vehicle A hybrid vehicle is one that uses two or more distinct types of power, such as submarines that use diesel when surfaced and batteries when submerged. Other means to store energy include pressurized fluid in hydraulic hybrids. The basic princip ...

. Electric transmission is usually classified as multiple separate transmission methods, according to engine type; for example, a vehicle powered by a

petrol engine A petrol engine (gasoline engine in American English) is an internal combustion engine designed to run on petrol (gasoline). Petrol engines can often be adapted to also run on fuels such as liquefied petroleum gas and ethanol blends (such as ''E ...

, using electrical transmission, would usually be classified as having petrol-electric transmission, despite the fact that the petrol engine is part of the

, the transmission being a separate system. Electric transmission was first used in the early 1920s. It was generally found to be unfavourable compared to the other methods available at the time, traditional steam locomotive transmission being up to 15% more efficient. However, by the late 1920s it was recognised as the best for larger vehicles.

Advantages and disadvantages

The primary advantage of electric transmission is that it does not require gear changes, which allows for smoother acceleration. It can also offer substantial advantages, as it reduces energy wastage which occurs in

mechanical transmission Propulsion transmission is the mode of transmitting and controlling propulsion power of a machine. The term ''transmission'' properly refers to the whole drivetrain, including clutch, gearbox, prop shaft (for rear-wheel drive vehicles), differ ...

, if the operator of the vehicle neglects to change the vehicle's gear. This is especially true in heavier vehicles, where the force required to start moving is very high compared to that needed to maintain speed if already in motion; hence this system is most used by

ships A ship is a large watercraft that travels the world's oceans and other sufficiently deep waterways, carrying cargo or passengers, or in support of specialized missions, such as defense, research, and fishing. Ships are generally distinguished ...

and

railway locomotive A locomotive or engine is a rail transport vehicle that provides the motive power for a train. If a locomotive is capable of carrying a payload, it is usually rather referred to as a multiple unit, motor coach, railcar or power car; the us ...

s; most

cars A car or automobile is a motor vehicle with wheels. Most definitions of ''cars'' say that they run primarily on roads, seat one to eight people, have four wheels, and mainly transport people instead of goods. The year 1886 is regarded as t ...

instead use mechanical transmission, as they have lighter loads, and are more lightweight. However, these cost savings are somewhat offset by the increased weight, and higher initial cost of the generator, wiring, and motor.

Applications

* Petrol-electric transmission, for use with

petrol engines A petrol engine (gasoline engine in American English) is an internal combustion engine designed to run on petrol (gasoline). Petrol engines can often be adapted to also run on fuels such as liquefied petroleum gas and ethanol blends (such as ...

. Substantially used in many industries in the early 20th century, but died out around the period of the

Second World War World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...

due to the greater popularity of

diesel engines The diesel engine, named after Rudolf Diesel, is an internal combustion engine in which ignition of the fuel is caused by the elevated temperature of the air in the cylinder due to mechanical compression; thus, the diesel engine is a so-calle ...

. Use today in combination with energy stored in a battery pack as a

hybrid electric vehicle A hybrid electric vehicle (HEV) is a type of hybrid vehicle that combines a conventional internal combustion engine (ICE) system with an electric propulsion system ( hybrid vehicle drivetrain). The presence of the electric powertrain is intende ...

* Diesel-electric transmission, for use with

. Mostly superseded petrol-electric transmission, taking much of the same markets. Much-used in

diesel-electric locomotive A diesel locomotive is a type of railway locomotive in which the prime mover (locomotive), prime mover is a diesel engine. Several types of diesel locomotives have been developed, differing mainly in the means by which mechanical power is conv ...

s and

diesel-electric multiple unit A diesel multiple unit or DMU is a multiple-unit train powered by on-board diesel engines. A DMU requires no separate locomotive, as the engines are incorporated into one or more of the carriages. Diesel-powered single-unit railcars are als ...

s, on railways. Used in some road vehicles such as buses and trucks in combination with a battery pack to store the energy needed to drive the electric motor used as a

Turbo-electric transmission A turbo-electric transmission uses electric generators to convert the mechanical energy of a turbine (steam or gas) into electric energy, which then powers electric motors and converts back into mechanical energy that power the driveshafts. Tur ...

, for use with steam turbine engines. Substantially used by ships, especially military warships. *

Turbine-electric transmission A turbine–electric transmission system includes a turboshaft gas turbine connected to an electrical generator, creating electricity that powers electric traction motors. No clutch is required. Turbine–electric transmissions are used to driv ...

, for use with

gas turbine engines A gas turbine, also called a combustion turbine, is a type of continuous flow internal combustion engine. The main parts common to all gas turbine engines form the power-producing part (known as the gas generator or core) and are, in the directi ...

. Has mostly superseded turbo-electric transmission. Much used in ships, and occasionally

gas turbine-electric locomotive A gas turbine locomotive is a type of railway locomotive in which the prime mover (locomotive), prime mover is a gas turbine. Several types of gas turbine locomotive have been developed, differing mainly in the means by which mechanical power is ...

s, on railways.

References

Automotive transmission technologies {{automotive-tech-stub

Advantages and disadvantages

Applications

See also

References