Penelope Cox Introduction to Engineering and Design, B6 11.29.11 PRODUCT EVOLUTION

The Electric Generator A generator is a machine that converts mechanical energy to electricity, utilizing the principal of electromagnetic induction, through which a moving magnetic field will generate an electric current in a conductive material.

Types of Electric Generator Dynamo Produces a direct current (a current that flows in one direction only) with the use of a commutator (a rotary electrical switch that periodically reverses the current direction). Alternator Produces an alternating current (a current that periodically reverses direction).

Uses For the most part alternators are more efficient than dynamos as they do not requite a commutator to keep the current produced flowing in one direction. Alternators are also lighter, cheaper, and do not have the disadvantage of having to have a commutator periodically replaced. Dynamos are used in low power applications where low voltage DC is required. Modern hand-cranked dynamos can be found in windup radios, hand powered flashlights, and cell phone chargers. Alternators are used in power stations, steam turbines, wind turbines (although indirectly) and cars (before the 1960’s dynamos were used to charge car batteries).

Timeline 1831 - Faraday discovers induction; Faraday’s disc 1832 - Ampere/Pixii Dynamo 1860 - Pacinotti’s Dynamo 1861 - Jedlik’s Dynamo 1866 - Alliance Generator 1867 - Siemens/Wheatstone Dynamo 1871 - Gramme Ring Dynamo

Faraday Discovers Electromagnetic Induction The first electric generator followed the English physicist Michael Faraday’s discovery of electromagnetic induction in 1831. In this first form of the electric generator a coil of copper (or other conductive material) was attached to a galvanometer/voltmeter and a magnet was inserted in the coil. The movement of the magnet within the coil generated an electric current which was then registered on the galvanometer.

Faraday’s Disc - 1831 Also known as Faraday’s wheel, this was the first of what are now known as homopolar generators. Developed by Michael Faraday during his experiments in 1831, Faraday’s disc operated by spinning a wheel of copper between two magnets, thus creating a current. Faraday’s disc was inefficient and was not a practical source of power, due to counterflow of current, although it led the way to the development of dynamos as we know them.

Ampere/Pixii Dynamo - 1832 In 1832 the French instrument maker Hippolyte Pixii developed the first dynamo based on Faraday’s original principles. It operated by rotating a permanent magnet with a crank. It had a spinning magnet, whose north and south poles passed a piece of iron wrapped with insulated wire. Each time a pole passed the coil a pulse of current was produced, although the poles of the spinning magnet produced currents in opposite directions. Although it was Pixii who invented this version of the dynamo, it was Andre Ampere, the French physicist and mathematician is credited with the discovery of electromagnetism, who suggested using a commutator to convert the alternative current to DC.

Pacinotti’s Dynamo - 1860 Around 1860, the Italian physics professor Antonio Pacinotti developed a dynamo that, instead of using a spinning coil with two magnetic poles, had a toroidal (donut-shaped) one, with multiple poles. This change fixed the issue earlier designs of the dynamo had experienced: “spikes” or pulses of current instead of a continuous flow of current, therefore heightening the average amount of power the dynamo produced.

Jedlik’s Dynamo - 1861 Around 1861 the Hungarian inventor and engineer Anyos Jedlik , after experimenting with electromagnetic rotating devices, developed his version of the dynamo. In Jedlik’s dynamo instead of two permanent magnets he used two electromagnets (magnets in which the magnetic fields is induced by a flow of electric current) opposite each other, which induced a magnetic field around the rotor.

Alliance Generator - 1866 In 1866, H. Wilde developed the commercially successful Alliance generator, which was used to power arc lamps in lighthouses. This generator employed permanent magnets.

Siemens/Wheatstone Dynamo - 1867 Dr. Ernst Werner Siemens, a German inventor and industrialist, coined the term “dynamo” in his announcement on January 7th, 1867 to the Berlin academy of his “dynamo-electric machine.” This was the first efficient version of the dynamo, as it used electromagnetic field coils rather than permanent magnets to produce current. The same year the English scientist Charles Wheatstone independently announced his development of a very similar machine, although at the time not having knowledge of Siemens’ invention. Leading directly to the first major industrial use of electricity, the Siemens dynamo was used in 1870s to power electric arc furnaces for the production of metal and other materials.

Gramme Ring Dynamo - 1871 Zenobe Gramme, a Belgian electrical engineer, invented the Gramme ring dynamo in 1871 whilst developing the first commercial power plants which operated in Paris in the 1870s. He basically reinvented Pacinotti’s design, producing a better path for magnetic flux and smoother current flow – much less “spikes” and pulses of charge. The Gramme ring dynamo was the first to generate commercial quantities of power for industry. Although further improvements have been made to the dynamo, Gramme’s basic design of a spinning endless loop of wire is the concept on which modern generators are built.

Bibliography Electric Generator. (2011). In Encyclopædia Britannica. Retrieved from http://www.britannica.com/EBchecked/topic/182624/electric-generator History of Electric Generator. (2005) In Wooden Generator. Retrieved from http://woodengenerator.com/History-Electric_Generator.html The Background And History Of Electrical Generators. (2011) In US Power And Environment. Retrieved from http://www.uspowerco.com/articles/background_and_history_of_electric_generators Generator. (2011) In BookRags. Retrieved from http://www.bookrags.com/research/generator-woi/ AC Power History And Timeline. (2011) In Edison Tech Center. Retrieved from http://edisontechcenter.org/AC-PowerHistory.html.