A turbo generator is an

electric generator In electricity generation, a generator, also called an ''electric generator'', ''electrical generator'', and ''electromagnetic generator'' is an electromechanical device that converts mechanical energy to electrical energy for use in an externa ...

connected to the shaft of a

turbine A turbine ( or ) (from the Greek , ''tyrbē'', or Latin ''turbo'', meaning vortex) is a rotary mechanical device that extracts energy from a fluid flow and converts it into useful work. The work produced can be used for generating electrical ...

(

water Water is an inorganic compound with the chemical formula . It is a transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance. It is the main constituent of Earth's hydrosphere and the fluids of all known liv ...

steam Steam is water vapor, often mixed with air or an aerosol of liquid water droplets. This may occur due to evaporation or due to boiling, where heat is applied until water reaches the enthalpy of vaporization. Saturated or superheated steam is inv ...

, or gas) for the generation of

electric power Electric power is the rate of transfer of electrical energy within a electric circuit, circuit. Its SI unit is the watt, the general unit of power (physics), power, defined as one joule per second. Standard prefixes apply to watts as with oth ...

. Large steam-powered turbo generators provide the majority of the world's electricity and are also used by steam-powered turbo-electric ships. Small turbo-generators driven by

gas turbine A gas turbine or gas turbine engine is a type of Internal combustion engine#Continuous combustion, continuous flow internal combustion engine. The main parts common to all gas turbine engines form the power-producing part (known as the gas gene ...

s are often used as auxiliary power units (APU, mainly for

aircraft An aircraft ( aircraft) is a vehicle that is able to flight, fly by gaining support from the Atmosphere of Earth, air. It counters the force of gravity by using either Buoyancy, static lift or the Lift (force), dynamic lift of an airfoil, or, i ...

History

The first turbo-generators were electric generators powered by water turbines. The first Hungarian water turbine was designed by the engineers of the Ganz Works in 1866; industrial-scale production with dynamo generators started only in 1883. Engineer Charles Algernon Parsons demonstrated a DC steam-powered turbo generator using a dynamo in 1887, and by 1901 had supplied the first large industrial AC turbo generator of megawatt power to a plant in Elberfeld, Germany. Turbo generators were also used on steam locomotives as a power source for coach lighting and water pumps for heating systems.

Construction features

Turbo generators are used for high shaft rotational speeds, typical of steam and gas turbines. The rotor of a turbo generator is a non-salient pole type usually with two poles. 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 solid

steel Steel is an alloy of iron and carbon that demonstrates improved mechanical properties compared to the pure form of iron. Due to steel's high Young's modulus, elastic modulus, Yield (engineering), yield strength, Fracture, fracture strength a ...

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, like mica and asbestos, are normally used in the slots of the rotor. These materials can withstand high temperatures and high crushing forces. 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.

Hydrogen-cooled turbo generator

Based on the air-cooled turbo generator, gaseous

hydrogen Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...

first went into service as the coolant in a hydrogen-cooled turbo generator in October 1937, at the Dayton Power & Light Co. in

Dayton, Ohio Dayton () is a city in Montgomery County, Ohio, United States, and its county seat. It is the List of cities in Ohio, sixth-most populous city in Ohio, with a population of 137,644 at the 2020 United States census, 2020 census. The Dayton metro ...

. Hydrogen is used as the coolant in the rotor and sometimes the stator, allowing an increase in specific utilization and a 99.0% efficiency. Because of the high

thermal conductivity The thermal conductivity of a material is a measure of its ability to heat conduction, conduct heat. It is commonly denoted by k, \lambda, or \kappa and is measured in W·m−1·K−1. Heat transfer occurs at a lower rate in materials of low ...

, high

specific heat In thermodynamics, the specific heat capacity (symbol ) of a substance is the amount of heat that must be added to one unit of mass of the substance in order to cause an increase of one unit in temperature. It is also referred to as massic heat ...

and low

density Density (volumetric mass density or specific mass) is the ratio of a substance's mass to its volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' (or ''d'') can also be u ...

of hydrogen gas, this is the most common type in its field today. The hydrogen can be manufactured on-site by

electrolysis In chemistry and manufacturing, electrolysis is a technique that uses Direct current, direct electric current (DC) to drive an otherwise non-spontaneous chemical reaction. Electrolysis is commercially important as a stage in the separation of c ...

. The generator is hermetically sealed to prevent escape of the hydrogen gas. The absence of

oxygen Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...

in the atmosphere within significantly reduces the damage of the windings' insulation by eventual corona discharges. The hydrogen gas is circulated within the rotor enclosure, and cooled by a gas-to-water

heat exchanger A heat exchanger is a system used to transfer heat between a source and a working fluid. Heat exchangers are used in both cooling and heating processes. The fluids may be separated by a solid wall to prevent mixing or they may be in direct contac ...

Notes

References

External links

Small Turbo-generator for DG & Hybrids
{{DEFAULTSORT:Turbo Generator Turbo generators