Electricity Generators

Except for remote, rural areas, electricity is everywhere running machines, vehicles, and appliances, and lighting and cooling, heating, and air conditioning homes and offices.   Yet, until the early 1800s, power, cooking, heating and lighting were provided by non-electrical sources, such as waterwheels, waterturbines, wood, coal, natural gas and coal gas.   Electricity changed, created and obsoleted many industries and in doing so increased living standards around the world, but particularly in Europe and the Americas, which had the money and technology to exploit electricity.

An electrical generator (alternator, dynamo) makes electricity by moving a wire coil on a shaft in a magnetic field produced by a magnet.   The generator transforms the mechanical energy of a rotating shaft into the electrical energy of an electrical circuit.   The origin generators produced 1-way (direct) pulsating current.   Improvements reduced the pulses to produce a more uniform direct current.   Later, generators were developed to produce alternating (2-way) current, which this may be transformed into direct (1-way) current by means of a commutator or rectifier.   Moving the shaft to produce electrical power requires a prime mover; that is, a steam, gas, or water turbine, or a nuclear reactor that drives the shaft connected to a generator.   Fuel burning in a boiler or uranium fissioning in a nuclear reactor boil water into high-pressure steam having high energy and force that propel turbine blades attached to a turbine shaft.   Burning gas propel the blades of a gas turbine.   Falling water propel the blades of a water turbine.   In regions with steady winds, windmills and wind turbines may be used to turn generator shafts very cheaply since the wind is free source of energy.   Where ample sunlight is available, the radiant energy of the sun (solar power) is collected in cells and funnelled to to batteries that, in turn, produce electricity.   The electricity generated by generator is transmitted via a power distribution system into factories, offices, and homes to produce light and power electric motors that powered machinery and appliances.     Small generators are useful too.   In automobiles, where they are called alternators, the battery provides the ignition system spark to start the engine, which turns the crankshaft, which turns the alternator shaft, which causes the alternator to produce AC (alternating electric current), which is changed to DC (direct electric current) by a device called a rectifier.   This electricity then powers lights, small motors, and other electrical equipment in the car, and also recharges the battery.

To 1800

Electricity at this time is a scientific curiosity.   Static charge is generated by friction and when the amount of charge become large, it arcs across poles as electricity (by definition, moving electric charge) to the amazement of onlookers.   A person was often put into the circuit so that the observers could see his hair stand on end.   (The person was not killed because the electric current was very small, so its force could not stop a heart.)   No useful work is done.   This status would change forever by an Italian named Alessandro Volta who invented the battery.

1800-1809

1810-1819

1820-1829

1830-1839

1840-1849

In the 1840s, Stoehrer of Leipzip improves the small scale generators used in laboratories. ^{Singer 181}

1850-1859

In 1855, Sóren Hjorth of Denmark receives a British patent for a generator in which he describes the principle of self-excitation, although he apparently never built one.   In self-excitation, the armature is wound with wire and the residual magnetism in the armature produces a current that increases the magnetism in the armature, which produces more current, etc., so that a powerful magnetic field is produced to produce a large current.   Until 1866 (see below), a separate electromagnet was used to produce the armature magnetic field. ^{Singer 183}

In 1856, E. W. von Siemens receives a British patent for a generator in which the coils of wire are kept within the magnetic armature.   It was called the H or shuttle armature.   This design reduces the size of generators. ^{Singer 184}

1860-1869

In 1861, Antonio Pacinotti, a professor of physics at the U. of Bologna, demonstrates a machine with a ring winding armature, enabling it to work as a generator or a motor from a battery.   It is described in an Italian journal in 1864. ^{Singer 188}

In 1866, S. A. Varley receives a patent for a self-exciting generator.   At about the same time, E. W. von Siemens submits a paper on the principle of self-excitation.   In 1867, Wheatstone also delivers a paper on self-excitation and demonstrates the principle with a working model built by A. Stroh. ^{Singer 185}   Other pioneers at this time are the Hungarian monk, Anyos Jedlik, a physics professor at the U. of Budapest, who discovers self-excitation in 1861, which is unknown to his contemporaries in western Europe, and Moses G. Farmer of Massachusetts, who claims to have discovered self-excitation in 1866.   He would later become a U.S. generator manufacturer.   These self-exciting generators were called "dynamo-electrics", which was later shorted to "dynamos". ^{Singer 187}

1870-1879

In 1870, Zénobe Théophile Gramme, a Belgian living in Paris, designs the first direct current generator using his Gramme ring armature first demonstrated by Pacinotti in 1861.   It is capable of producing a continuous (in contrast of pulsating) direct current without overheating.   These generators enter commercial production in 1874 and lead to the first power station installations. ^{Singer 188-189}

In 1872, a generator with a drum armature is invented by F. von Hefner Alteneck.   It is more efficient than the Gramme armature because more of its winding generated electricity. ^{Singer 189-190}

With practical commercial generation now available, motors can be developed commercially.   In 1873, Gramme and Fontaine exhibit in Vienna a reversible combination of 2 Gramme direct current generators, one acting as a generator to run the other acting as a motor. ^{Singer 231}

1880-1889

1890-1899

1900-1909

1910-1919

1920-1929

1930-1939

1940-1949

1950-1959

1960-1969

1970-1979

1980-1989

1990-1999