The electrification of the world

Werner von Siemens and the dynamoelectric principle



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.

A long journey – First steps towards new lighting technology

In the fall of 1866, Werner von Siemens was spending more time on the question of how to improve spinning dynamos as they existed at that time. The only usable sources of electricity at that time were electrochemical batteries and simple spinning dynamos, but these options lacked the power to be used for anything but telegraphic purposes and small galvanic applications. Fields of application in the area of heavy electrical engineering, such as street lighting or even electrical power plants, were still impossible.


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.

The double-T armature – The basis for higher rotational speeds

These weaknesses served as the starting point for Werner von Siemens’ systematic research. Achieving higher rotational speed for the armature and generating stronger magnetic fields were decisive factors in his success at enhancing the design of magneto-electric machines. The double‑T armature that the electrical pioneer Werner von Siemens had initially developed for his pointer telegraph provided the basis for achieving much higher rotational speeds in dynamos. His design offered sufficient mechanical strength.


In 1864, the Englishman Henry Wilde had made the first attempt at replacing the weak steel magnets used in generators with electromagnets that were in turn produced by the conventional dynamos of that era. Not satisfied by this technically incomplete solution, Werner von Siemens once again enabled a crucial developmental advance: in September 1866, he had his workshop connect a double-T armature of a generator in series with an electromagnet so he could explore the effect of self-induction. When the double‑T armature was then cranked by hand, the slight magnetism of the Earth was sufficient for initial low-level generation of electricity (self-induction). This energy field then strengthened itself and reached full strength after a few rotations. As a result, a connected electroscope measuring device immediately burned through, and it was even possible to melt a one-meter-long iron wire secured between the generator clamps.

The beginning of heavy-current electrical engineering – The Siemens & Halske dynamo machine

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.
Werner von Siemens, 1866

Lighter, more efficient and less expensive – The dawn of a new era of electrification

After several weeks of testing, Werner von Siemens was certain that his new dynamo-electric machine had the potential to enable substantial developmental progress. Compared with dynamos using permanent magnets, it could reduce the weight of the drive unit by 85 percent, the necessary drive power by about 35 percent, and the price of the machine by 75 percent – while maintaining the same power. A great technological advance! Now electric power could be generated inexpensively and used at much higher capacities. This made electromotor drives possible – and economical – for technical applications for the first time. The foundation had been laid for today’s use of electric energy in all areas of life.


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 innovation, 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. 



Volker Leiste | Dr. Ewald Blocher