Turbine-electric powertrain

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 drive both gas turbine locomotives (rarely) and warships. A handful of experimental locomotives from the 1930s and 1940s used gas turbines as prime movers. These turbines were based on stationary practice, with single large reverse-flow combustors, heat exchangers 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 railcars rather than separate locomotives. 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. 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 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 Zumwalt-class—allows a gas driven turbine to run generators. 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.