Developments

Dynamo


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Werner von Siemens laid the foundations for a new age of electricity. Faster than others, he recognized the potential of the dynamoelectric principle and applied the maxim that the value of an invention is in its practical application. The dynamo machine that the company developed to market maturity was the prerequisite for putting electricity to use in everyday life. By providing an economical way to turn mechanical energy into electrical energy, it marked the beginning of the electrification of the world.

The first steps toward using batteries or generators for purposes such as illumination had been taken at an early stage. In 1808, English physicist Humphry Davy had produced an electric arc for lighting purposes for the first time, thus proving that what he called electric “arc” lamps could emit a much brighter and more intense light than other light sources being used at the time. As a result, electric arc lamps could be used to make lighthouses along the coasts much more visible or to illuminate large construction sites or other public areas.

An industrial building was located immediately adjacent to the objects to be lit and used to store the spinning dynamos that powered the arc lamps. These generators – known as magneto-electric machines – were heavy but not very powerful and used permanent magnets. The machines produced barely 700 Watts, although the generators weighed almost 2,000 kilos. In addition, power generation was subject to very strict limits, because the permanent steel magnets that were used produced only a weak magnetic field. Furthermore, they easily lost their magnetism due to the vibrations caused by operation.

In early December 1866, Werner von Siemens reported on his experiments with the new dynamo machine to his brother William. Looking at the commercial potential of his invention, he wrote: “Provided the design is correct, the effects should turn out to be enormous. This concept can well be expanded and may initiate a new era in electromagnetism. Thus, magnetic electricity will become available very inexpensively, and lighting, galvanometallurgy, etc., even small electromagnetic machines obtaining their energy from larger ones, may become feasible and useful.” At the same time, Werner von Siemens was preparing his report “On the transformation of mechanical energy into electric current without the application of permanent magnets,” which was presented by his friend Heinrich Gustav Magnus before the Prussian Academy of Sciences on January 17, 1867. This brought Werner von Siemens’ brilliant discovery to the attention of experts in the field.

In the most basic sense a generator/dynamo is one magnet rotating while inside the influence of another magnet’s magnetic field. You cannot see a magnetic field, but it is often illustrated using lines of flux. In the illustration above lines of magnetic flux would follow the lines created by the iron filings.

The generator/dynamo is made up of stationary magnets (stator) which create a powerful magnetic field, and a rotating magnet (rotor) which distorts and cuts through the magnetic lines of flux of the stator. When the rotor cuts through lines of magnetic flux it makes electricity.