View source for Turbine-electric powertrain

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[[File:Union Pacific 18.jpg|thumb|right|[[American Locomotive Company|ALCO]]-[[General Electric]] [[Union Pacific GTELs]] [[gas turbine–electric locomotive]]. X-18 is one of the third series, built 1958–61.]]
[[File:Rtg limoges.jpg|thumb|[[Turbotrain]]s were [[gas turbine train]]s built in France 1971–75 and supplied to [[SNCF]], [[Amtrak]] and [[Islamic Republic of Iran Railways|Iranian Railways]].]]
A '''turbine–electric transmission''' system includes a [[turboshaft]] [[gas turbine]] connected to an [[electrical generator]], creating [[electricity]] that powers [[electric motor|electric]] [[traction motor]]s. No [[clutch]] is required.

Turbine–electric transmissions are used to drive both [[gas turbine locomotive]]s (rarely) and [[warship]]s.

==Locomotive applications==
A handful of experimental locomotives from the 1930s and 1940s used gas turbines as [[prime mover (locomotive)|prime mover]]s. These turbines were based on stationary practice, with single large reverse-flow [[combustor]]s, [[heat exchanger]]s and using low-cost heavy oil [[bunker fuel]]. In the 1960s the idea re-emerged, using developments in light weight engines developed for helicopters and using lighter [[kerosene]] fuels. As these turbines were compact and lightweight, the vehicles were produced as [[railcar]]s rather than separate locomotives.

==Naval applications==
Gas and steam turbines are most efficient at thousands of revolutions per minute. This is a major drawback because of the need for heavy gears, which drive the engine into one single duty, propulsion. Electric motors provide numerous applications including use of accessories besides that of propulsion.<ref name="GAS TURBINES AND DIESEL ENGINES">{{cite news|last1=Schmalzer|first1=Bill|title=GAS TURBINES AND DIESEL ENGINES: COOPERATION WITH INTEGRATED ELECTRICAL DRIVES|issue=5|publisher=Monch Publishing Group|date=2011}}</ref>

Warships require the ability to cruise efficiently for long distances and also to have high power for intermittent bursts of speed. For that reason they use combined power systems that use an efficient prime mover, such as a [[marine diesel engine|diesel engine]] or a small gas turbine, for cruising and large gas turbines for high speed. Most of these use mechanical combination of power, through gearboxes and clutches, with systems such as [[CODOG]] (Combined Diesel or Gas) or [[COGAG]] (Combined Gas And Gas). Where electric transmissions are used, this is referred to as [[integrated electric propulsion]] or IEP.

A guided missile destroyer—for example the [[USS Zumwalt|''Zumwalt'']]-class—allows a gas driven turbine to run generators.<ref name="GAS TURBINES AND DIESEL ENGINES" /> This generator can produce electricity to move the ship and also operate a variety of its instruments and accessories. A lot of these electricity-generating turbines are being produced to include integrated electrical propulsion. Integrated electrical propulsion is when the engine strictly runs off of electricity, without the use of any gasoline, diesel, or fuel for that matter. The electric engine is more efficient due to only being electric and not gasoline based. It allows for less pollution and provides electricity to the naval ships instruments and applications. A lot of these electricity-generating turbines are being produced to include integrated electrical propulsion.<ref name="GAS TURBINES AND DIESEL ENGINES" /> A good example of one of these systems is the COGAL (combined gas and electric) system.<ref name="GAS TURBINES AND DIESEL ENGINES" />

An alternative approach is to use [[COGES]], Combined Gas–Electric and Steam, to improve overall efficiency. A gas turbine-electric primary transmission is used, with a [[heat-recovery boiler]] in the exhaust flow to generate steam and thus electricity via a secondary [[steam turbine]]. Electric driven propulsion allows for movement of the ship and provides power generation on-board of the ship.<ref name="GAS TURBINES AND DIESEL ENGINES" /> Heat lost by gas turbines is not practical because it is wasting energy as heat dissipates into the surroundings. The COGES system allows the heat to be captured and converted into steam for the generation of electricity.<ref name="GAS TURBINES AND DIESEL ENGINES" /> Unlike diesel and other heavy-fuel turbines, the COGES captures the left over heat and exhaust from the turbine and it reduces pollutants from escaping into the atmosphere.<ref name="GAS TURBINES AND DIESEL ENGINES" /> The COGES system allows for practical applications in cruise ships, for example the [[General Electric LM2500]].<ref name="GAS TURBINES AND DIESEL ENGINES" />

==See also==
{{div col|colwidth=23em}}
* [[Diesel–electric transmission]]
* [[Gas turbine]]
* [[Gas turbine–electric locomotive]]
* [[Integrated electric propulsion]]
* [[Turbine]]
* [[Turboshaft]]
{{div col end}}

==References==
{{Reflist}}

==Further reading==
* {{cite web |url=http://www.americanscientist.org/issues/pub/the-adaptable-gas-turbine/1 |title=The Adaptable Gas Turbine » American Scientist |website=www.americanscientist.org |url-status=dead |archive-url=https://web.archive.org/web/20150402121738/http://www.americanscientist.org/issues/pub/the-adaptable-gas-turbine/1 |archive-date=2015-04-02}} – an article on the many uses of gas turbines

[[Category:Electric power]]
[[Category:Engine technology]]
[[Category:Gas turbine locomotives]]
[[Category:Gas turbine technology]]
[[Category:Marine propulsion]]
[[Category:Turbo generators]]