Aturbo generator is anelectric generator connected to the shaft of aturbine (water,steam, orgas) for the generation ofelectric power.[note 1] Largesteam-powered turbo generators provide the majority of the world's electricity and are also used by steam-poweredturbo-electric andgas-turbine-electric powered ships.[1]
Small turbo-generators driven bygas turbines are often used asauxiliary power units (APU, mainly foraircraft).
The first turbo-generators were electric generators powered bywater turbines. The first Hungarian water turbine was designed by the engineers of theGanz Works in 1866; industrial-scale production with dynamo generators started only in 1883.[2] EngineerCharles Algernon Parsons demonstrated a DC steam-powered turbo generator using adynamo in 1887,[3] and by 1901 had supplied the first large industrialAC turbo generator of megawatt power to a plant in Elberfeld, Germany.[4]
Turbo generators were also used on steam locomotives as a power source for coach lighting andwater pumps for heating systems.
Turbo generators are used for high shaft rotational speeds, typical of steam and gas turbines. Therotor of a turbo generator is anon-salient pole type usually with two poles.[5]
The normal speed of a turbo generator is 1500 or 3000 rpm with four or two poles at 50 Hz (1800 or 3600 rpm with four or two poles at 60 Hz). The rotating parts of a turbo generator are subjected to high mechanical stresses because of the high operation speed. To make the rotor mechanically resistant in large turbo-alternators, the rotor is normally forged from solidsteel and alloys like chromium-nickel-steel or chromium-nickel-molybdenum are used. The overhang of windings at the periphery will be secured by steel retaining rings. Heavy non-magnetic metal wedges on top of the slots hold the field windings against centrifugal forces. Hard composition insulating materials, likemica andasbestos, are normally used in the slots of the rotor. These materials can withstand high temperatures and high crushing forces.[6]
The stator of large turbo generators may be built of two or more parts while in smaller turbo-generators it is built up in one complete piece.[7]
Based on the air-cooled turbo generator, gaseoushydrogen first went into service as thecoolant in ahydrogen-cooled turbo generator in October 1937, at theDayton Power & Light Co. inDayton, Ohio.[8] Hydrogen is used as the coolant in the rotor and sometimes thestator, allowing an increase in specific utilization and a 99.0% efficiency. Because of the highthermal conductivity, highspecific heat and lowdensity of hydrogen gas, this is the most common type in its field today. The hydrogen can be manufactured on-site byelectrolysis.
The generator is hermetically sealed to prevent escape of the hydrogen gas. The absence ofoxygen in the atmosphere within significantly reduces the damage of the windings' insulation by eventualcorona discharges. The hydrogen gas is circulated within the rotor enclosure, and cooled by a gas-to-waterheat exchanger.[9]
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