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As electrification (in Switzerland and electrification ), also dated electrification , it is generally the provision of infrastructure in the form of power grids to supply a region or country with electric power respectively. It began as a result of the industrial revolution in the 1880s and is a continuous process. As an essential property, electrification on a large scale enables the spatial separation between the energy consumer, for example an electric drive or lighting, and the power plant , in which various primary energy sources are usedconverted into electrical energy. In the industrial sector, electrification made it possible to replace spatially restricted and mechanically complex energy distribution systems such as transmission shafts .

Historical developments

Electric lighting

Advertisement for electric lights around 1919

Electrification was mainly initiated by the advent of electrical lighting and the discovery of the dynamo-electric principle , which was essential for the provision of larger amounts of electrical energy. First of all, larger events such as the World Exhibition in Paris in 1878 were equipped with the new carbon arc lamp . Various other areas followed, such as theater lighting , because open fires such as oil and gas lighting repeatedly led to accidents such as the Vienna Ringtheater fire . The lighting of the public space in the form of street lighting also supported the expansion.

The carbon arc lamps or Yablotschkow candles that were initially used were too expensive and time-consuming for private households or had the disadvantage of developing odor or noise.

The carbon filament lamp , a type of incandescent lamp that uses an electric current to make a filament of carbon glow , found widespread use, particularly in wealthy private households or hotels . In 1878 the Briton Joseph Wilson Swan developed a low-resistance carbon filament lamp with a comparatively thick and easy-to-produce filament, which, however, could only be operated at low voltages. In 1879 Thomas Alva Edison developed a carbon filament lamp with a thin carbon filament that is more difficult to manufacture for an operating voltage of around 100  volts , which achieved the economic breakthrough. The higher voltage made it possible to distribute electricity in the form of first direct current networks. Edison was one of the first to recognize the potential of electric lighting and to use it commercially.

In the beginning, however, the carbon filament lamp was not very competitive in terms of price compared to gas lighting , especially the gas light improved by Carl Auer von Welsbach . Only in the course of time could the carbon filaments be replaced by incandescent lamps with metal filaments made of various metals with very high melting points such as tungsten, which are still common today . This enabled higher performance, a longer service life and, with the same brightness, a reduction in energy consumption. The incandescent lamp quickly replaced the gas lighting. The rotary switches that are still in use today are based on the rotary valves of the gas lighting of that time.

Electric motors

Two-phase synchronous motor, built in 1893

In addition to electrical lighting and electrical heating , electrical drives were of great importance from the beginning of electrification. Werner Siemens patented his dynamo machine in 1866 , the construction of which helped the electric motor as a drive machine to achieve a breakthrough in a wide range of practical applications. The design of electric motors has been improved over the years, so that the need for electrical energy for drives grew and in Berlin at the turn of the century (1900) it exceeded the energy requirement for lighting purposes, then also known as "luminous flux" for the first time.

In factories, compact electric motors increasingly replaced the usual steam engines, gas engines, water power plants and transmissions . This also led to an appreciation of the craft, since mechanical energy was now readily available everywhere. Industrial companies often created their own power plants, for example Märkisches Elektrizitätswerk , which not only supplied electrical energy but also process heat. Even so, until the First World War, electrification still took place mainly in the cities or in particularly suitable locations.

Power grids

Thomas Alva Edison

The first applications of electricity, e.g. in electroplating technology or for lighting purposes, took place in simple networks that linked the producer directly to the consumer. Both DC and AC voltage generators were used, the latter for example for lighting with arc lamps or in lighthouses. The advantage of the electrical energy supply, however, is the simple possibility of energy distribution through electrical networks, with the help of which excess energy can be given to interested parties, or several generators can be interconnected to form a network for trouble-free operation. A basic distinction is made between two types of electricity networks, DC and AC voltage networks. The latter gained acceptance more slowly due to their greater complexity, but they are more important today.

DC voltage networks

In the early days of electrical energy technology around the years 1880 to 1900, there were smaller, local power grids in the form of island grids that were operated with direct voltage . Direct voltage is technically suitable for supplying light bulbs and the direct current motors available at the time, at that time there were no practical alternating current motors available. In addition, direct voltage networks allow direct connection with accumulators for electrical energy storage, which basically only work with direct voltage. Rectifiers that are common today and their counterparts, the inverters , were not yet available at that time.

Circuit diagram of Edison's three-wire system for direct voltage
Edison's DC generator Jumbo

Edison preferred DC voltage systems, in which a constant load flows a DC current , because he held various patents on DC voltage equipment and did not want to lose income from it. Edison developed one of the first electricity meters to measure the consumption of electrical energy and to be able to bill it accordingly. This electricity meter, known as the Edison meter, could only record direct currents. Edison's first power grids, such as Pearl Street Station and the one shown in simplified form in the adjacent circuit diagram, provided for a small power station in each district and consisted of direct current generators , labeled G1 and G2 in the sketch . These local Edison power grids had a spread of about 1.5 km in diameter. The type Jumbo DC generator he developed weighed 24 t and had around 100 kW of power, which was sufficient for around 1200 light bulbs .

This of steam engine driven generators produced a so-called bipolar DC voltage with respect to ground potential respectively to an outer conductor of a positive DC voltage of +110 V and a second outer conductor, a negative voltage of -110 V. As a result are, with the center conductor to ground potential is, a total of three conductors are required, which is why this form is also referred to as a three-wire network.

The combination of two generators and a voltage that was positive and negative with respect to earth potential made two different DC voltages available to the consumers: 110 V and 220 V. A common consumer at the time was the carbon filament lamp , a first type of incandescent lamp. Carbon filament lamps were operated with voltages around 100 V and connected between earth and one of the two outer conductors. The number of lamps was divided as evenly as possible between the two outer conductors. Other major consumers at the time were electric DC motors for mechanical drives, for example for machine tools. Due to their higher power compared to incandescent lamps, DC motors were designed for a higher voltage of 220 V and connected between the two outer conductors. As a result, the cross-sections of the cables could be kept within reasonable limits so that the voltage loss along the line would not increase too much.

This form of three-wire network according to Edison is common in low-voltage networks in North America today in the form of single-phase three-wire networks . However, the three-wire arrangement is operated with AC voltage and a mains frequency of 60 Hz. The principle of Edison with two different high voltages (the low voltage for the operation of low-power devices such as lighting and a high voltage for devices with high power consumption such as tumble dryers) has been retained. Indistinguishable from Edison's three-conductor systems today are available three-phase connections , which are common, especially in Europe. There are also two different voltages available, which however have a different relationship to one another than in single-phase networks due to a different concatenation factor . In addition, with three-phase alternating current, a rotating field is available for the direct drive of rotating-field machines such as asynchronous motors , which is fundamentally not available in single-phase three-wire networks.

Direct current is of no importance in today's meshed power grids such as the interconnected network , as the availability of high-performance rectifiers means that consumers that require direct voltage - such as electronic devices - can generate the necessary direct voltage in the device. Subways , roads and some full trains run from historical reasons still with direct current. In the power supply DC is for connections between two points in the form of high-voltage direct current (HVDC) for transporting the electrical energy over long distances or in submarine cables used to reactive power problems to be avoided or to different AC networks to each other in the form of the HVDC short coupling link to be able to.

AC voltage networks

Alternator , manufacturer: Compagnie L'Alliance
Transformer by Bláthy , Déri and Zipernowsky

The generation of electrical alternating currents had been known for a long time, but was not used at the beginning of electrification, as the first inventors had committed themselves to direct voltage when electrifying New York . In addition, important components when using alternating current, transformers and alternating voltage motors, had not yet been invented. After all, individual AC voltage systems were used for lighting with arc lamps.

The decisive breakthrough in AC voltage networks came with the use of several phase-shifted AC voltage sources to form a multi-phase system, as discovered by various inventors in the 1880s. In particular, Tesla with its originally two phases shifted by 90 °, which also included 3-phase systems, especially three -phase systems, through generally held patents , should be emphasized here. According to S. Kalischer, the term “three-phase current” goes back to Dolivo-Dobrowolsky . He was therefore also in charge of the spread of three-phase AC technology in Germany.

The spread of AC voltage technology was among other things. hampered by patents and regulations. At that time, under patent law , manufacturers often limited the right to use the incandescent lamps sold to the licensed power grids. Hotels and offices with their own generators were successfully ordered to refrain from using their light bulbs. The light bulb manufacturers thus also secured the market for electrotechnical infrastructure and hindered free competition and innovation. These effects of patent law were criticized in the newspapers of the time. In contrast to Edison , the entrepreneur George Westinghouse was unable to offer his customers a complete solution, including a power supply, as he did not have any patent rights for the production of incandescent lamps. Post and railway companies feared for their existing infrastructure, so that operators of electrical lines were placed under considerable conditions in the form of regulations.

Development of the transformer

The first work on transformers in the first power grids by Lucien Gaulard and John Dixon Gibbs dates back to the early 1880s and, as so-called air transformers, were very inefficient. These transformers had an open magnetic circuit and thus a high magnetic leakage flux . With these first transformers, it was possible to bring the high alternating voltage for distribution - the high voltage was necessary over longer distances to minimize losses - to lower voltages of around 100 V for supplying individual incandescent lamps. The term transformer was not yet common at the time; the devices were called "secondary generator". The assignment of transformers to the area of electrical machines , which is still common today, is derived from this.

However, with the transformer according to Gaulard and Gibbs, there was a strong load dependency, because the switching on and off of individual incandescent lamps resulted in voltage changes due to the series-connected primary windings of the air transformers as well as the high leakage flux and the only low magnetic coupling, with which the individual lamps AC voltage consumers had a mutually disturbing influence. In the case of incandescent lamps, this led to different brightness levels, depending on how many incandescent lamps were currently switched on in the neighborhood. To reduce this disruptive effect, a control in the form of a magnetic rod was provided in the center of the transformer, which could be pulled out a little or pushed into the structure in the event of voltage fluctuations.

The Hungarians Károly Zipernowsky , Miksa Déri and Ottó Titusz Bláthy succeeded in improving these first transformers in 1885 with a magnetically closed transformer core, similar to today's toroidal transformers . In addition, the primary sides of the individual transformers were not connected in series but in parallel , which meant that the mutual influence of the individual incandescent lamps was negligibly small. The transformer made it possible to achieve higher electrical voltages, and thus the electrical power could be transported over longer distances with comparatively low transmission losses . This basic principle is used today in electrical power engineering .

Development of the AC motor

The generation of alternating voltage with alternating voltage generators had been known for a long time and brought to market maturity in the form of the Alliance machine. However, the reversal of the inductor principle on which it is based did not succeed in a satisfactory manner. The first motors could only deliver significant energy in synchronism and had to be brought into this state by external forces (for example a DC motor).

By adding a commutator and a field coil, Károly Zipernowsky was able to develop the single-phase AC motor derived from DC machines. This became widespread as a series motor or all-current motor . Due to the commutator and the high iron losses, these motors had some disadvantages, which among other things led to the operation of such motors at low mains frequencies (see traction current ). All-current motors are also used in various household appliances.

The breakthrough came with the introduction of multi-phase current, especially 3-phase three-phase current. Several inventors (including Tesla , Doliwo-Dobrowolsky or Haselwander ) found different arrangements almost simultaneously around 1890 that could be used as a three-phase generator or motor.

Public relations for the spread of electricity

In the period from 1881 to 1891, the latest electrotechnical achievements were regularly presented to a large audience in the form of international electricity exhibitions, aroused corresponding desires and thus increased demand. The International Electrotechnical Exhibition of 1891 deserves special mention , which, as part of the three-phase current transmission Lauffen – Frankfurt over 176 kilometers, showed for the first time that highly transformed alternating voltage could be transported over greater distances. The relatively simple structure of the electrical energy transmission with a transmission power of over 100 kW predestined it as a possibility for power transmission , which at that time was still implemented on a small scale with pressurized water , transmissions or compressed air . The 57-kilometer direct current long- distance transmission from Miesbach to Munich, which had been put into operation nine years earlier in 1882 , had a transmission capacity of around 1 kW by comparison.

Establishment of institutes, associations and companies

The 110 kV line Lauchhammer – Riesa built in 1912 was the first high-voltage line with more than 100 kilovolts in Germany

In addition to technology, knowledge about electricity also had to be disseminated and standards had to be agreed. In Germany, the Elektrotechnische Verein eV was founded in 1879 , a forerunner of the VDE , and in 1883 a chair for electrical engineering was established for the first time (see Erasmus Kittler ). In 1887, the Physikalisch-Technische Reichsanstalt , initiated by Siemens , was founded, which was not only dedicated to important questions of standardization and basic research in the field of electricity.

The founding of well-known electrical engineering companies also fell during this period, for example Helios in 1882 , AEG in 1887, BBC in 1891, Schuckert & Co. 1893, Siemens Werke 1897. Before the First World War , the German electrical industry assumed a share of around 50% the leading position in world production.

In medicine, electricity has been used for a long time, not least the discoveries of Luigi Galvani can be traced back to its use. The negative or harmful effects were also examined; In Vienna in 1929 a chair for electropathology was set up by Stefan Jellinek , who had been studying electrical accidents and their prevention since 1899.

Temporal development and network expansion

The first major company to offer a general power supply both power and luminous flux were in 1884 by Emil Rathenau founded Berlin Elektricitäts works . The supply was provided by an increasing number of block stations that supplied consumers within a radius of approx. 800 m. Elsewhere, industrial companies such as collieries took over the power supply by supplying neighboring communities or interested parties. The early power plants initially had severe problems with utilization and a very poorly balanced load profile : While electricity was initially only used for lighting purposes, more and more power was required later during the day, while only small amounts of energy were required in the evening or at night, making it no longer economical to operate large generators made appear. This imbalance could only be partially countered with electrochemical energy storage in the form of accumulators . In addition, the increasing spread demanded a higher security of supply , which would have required considerable redundancies in isolated operation . Therefore, the power plants were constantly networked with one another, even over long distances by means of intercity centers , and the forerunners of today's interconnected networks were formed . In addition, the urban power plants could often no longer provide the required output on their own, which is why after the introduction of the alternating current or three-phase power plants, these were located outside the cities, or in places where primary energy sources were particularly cheap.

The number of power plants grew by leaps and bounds by 1913, as the following table shows based on the installed capacity :

1891 1895 1900 1906 1913 1925 1928 1948 1956 2000 2016
Number of works 9 148 652 1338 4040 3372 4225 - - - -
Capacity [MW] 11.6 40 230 720 2,100 5,683 7,894 6,175 18,900 121,296 215.990
Average Output per plant [MW] 0.27 0.35 0.54 0.52 1.69 1.87 - 4.5 - -

The use of larger units reduced the number of plants, while the installed capacity continued to increase. Due to the war, the installed capacity in 1948 was lower than in 1928. The doubling of the installed capacity between the years 2000 and 2016 is due to the expansion of renewable energy generation. However, the installed capacity of the regenerative energy producers is not continuously available, which is reflected in the statistics of the full load hours , which are around 7000 h / a for nuclear power plants and 914 h / a for photovoltaics.

Rural electrification in the US, 1930s

In the 1920s, the advantages of electrical energy led to an explosion-like expansion, even in rural areas, which in some cases was promoted by the general staff, for example in Bavaria by Oskar von Miller . Electrification was often implemented by private companies such as mills, distilleries and sawmills, but also "electricity offices" and, especially in rural areas, also by cooperatives or even foundations, some of which also took on the development of gas and water supplies. For example, PreussenElektra came into being in 1927 from the merger of the Prussian electricity authorities and investments by the Prussian state and some municipal utilities. In 1931, PreussenElektra launched a special loan and rental system called “Elthilfe” in order to facilitate the acquisition of electrical devices and thus increase electricity sales.

In the US, the electrification of rural areas was only implemented in the 1930s as part of the " New Deal " in the form of job creation measures, since in 1934 only 11% of all US farms had an electricity connection, while in European countries such as France and Germany at the same time around 90% of all farms were electrified. In the Soviet Union , with the GOELRO plan passed in 1920, the expansion of the power grid in line with Lenin's slogan “Communism - that is Soviet power plus the electrification of the whole country” was the official state doctrine.

In the course of time, the high costs of electrification led to a monopoly in the electricity industry , through which most of the public or cooperative energy supply companies (EVU) were merged into the large EVUs known today. This monopoly was initiated by the Energy Industry Act of 1935. The law was originally intended to protect the not inconsiderable investments, to promote electrification and to make electricity cheaper through standardization and pooling of resources, but led to a strong dependency of customers on their utility company, which was only abolished, at least in theory, by an amendment to the liberalization of the electricity market . The advantages and disadvantages of public or private energy supply are still a topic of discussion today. The challenges at that time could only be handled by solvent institutions (large companies, public authorities).

Convergence of the systems

After the current war there were widespread and, depending on the region, different direct current and alternating current networks that worked with different voltages and different network frequencies until the 1950s. The direct current supply was finally discontinued in Frankfurt am Main in 1959 and replaced by alternating current. In three-phase and the number of phases were initially discussed: So favored Nikola Tesla the two-phase electric power , it is today stepping motors used while Mikhail of Dolivo-Dobrowolsky with colleagues at AEG, the now common system of the three-phase alternating current developed.

The diversity of the power supply systems was due to local conditions and the different systems that were often used to exclude competitors. The different shapes led to complications when purchasing electrical devices, which could only be partially offset by the development of so-called all - current devices , such as the first tube receiver in the 1920s and 1930s. In addition, there were patent law difficulties, for example the use of three-phase current was initially hindered by the Nikola Tesla patents .

Grid frequency

The use of alternating current with a mains frequency of 50  Hz in European countries is said to go back to Emil Rathenau , founder of AEG . An AEG publication stated in 1901: "This number of 100 changes is the number of seconds that AEG has assumed to be normal for its three-phase systems" , with 100 changes or zero crossings per second corresponding to a frequency of 50 Hz. However, 50 Hz was already common with the first commercial alternators, the Alliance machines , a special form of inductor . In addition to change number and terms such as at the time were number of cycles , number of pulses or periods of use. The first AC power plants and the installations of the Berliner Elektricitäts-Werke (BEW) were designed for 50 Hz. From then on, the 50 Hz prevailed through the "normative force of the factual" in Germany, since a merger of energy networks at that time could only take place with the same frequency selection or with the help of converters . Standardization takes decades. The following network frequencies were common in Europe around 1946:

Frequency (Hz) region
25th In parts of: France, Germany, Sweden, UK
40 In parts of: Belgium, Switzerland, UK
42 In parts of: Czechoslovakia, Hungary, Italy, Portugal, Romania
45 In parts of: Italy
50 Primary network frequency in most of Europe
100 Exclusive to: Malta

The reasons for using 60 Hz in the US are much better documented. The chosen frequency of 60 Hz was a compromise between the requirements of large machines for the lowest possible frequencies and those of electrical lighting, which required the highest possible frequencies because of the flicker , which was particularly annoying with arc lamps.

As the country overview of network frequencies and voltages shows, there are only a few areas today, neither those according to the US, nor those according to Western European influence, either 60 Hz or 50 Hz as the network frequency. In the Arab world, for example, a network frequency of 60 Hz is used in Saudi Arabia , whereas a network frequency of 50 Hz is used in neighboring Gulf states such as the United Arab Emirates and Qatar . In the power grid in Japan , different mains frequencies of both 50 Hz and 60 Hz are used in different parts of the country, which goes back to the different suppliers of basic electrical equipment in the different parts of the country at the beginning of the 20th century. The frequency of 50 Hz has the greatest global distribution.

Mains voltage

The line voltage in the low-voltage network was set quite early in the USA at 110 V or twice the value of 220 V for electric drives. The doubling results from the connection of the single-phase three-wire network with center tap. The choice of 110 V was motivated by Edison's carbon filament light bulbs, which were designed for 100 V, and for which a reserve for the voltage drop on the lines was required.

In Europe, the voltage in the low-voltage network was doubled to 220 V in order to minimize losses. However, in Germany, especially in rural areas, there were individual grids with 110 V until the 1960s. As part of the system convergence and the displacement of direct current grids, practically all connections in Europe were converted to the three-phase system with a neutral conductor . The voltage of 220 V to 240 V between an outer conductor and the neutral conductor remained at the target value of 220 V to 240 V, from 1985 these slightly different voltages were harmonized to 230 V, the voltage between two outer conductors is the voltage of , which is higher by the concatenation factor 380 V (or 400 V) and is intended for the connection of larger loads and electrical drives.

While uniform voltages are used in the high- voltage networks with more than 110 kV and in the low- voltage range, the medium-voltage level , which is operated by local electricity suppliers, often has various voltage levels for historical reasons. In addition to standardization, the standardization is driven by the high additional costs that a special voltage would entail.

Electrification today

Electrification is not yet complete worldwide. According to the International Energy Agency (IEA), there are more than 1.4 billion people without access to electricity. Most of them live in sub-Saharan Africa (589 million) and Asia (930 million). In view of the slow progress in electrification in many countries, the numbers are expected to decline only slowly. For Africa, the IEA is even forecasting an increasing number of people without access to electricity by 2030.

The greatest challenge here is rural electrification. In many African countries, less than 20% of the rural population has access to electricity. Due to the lack of capital in these countries and the relatively low demand for electricity in rural areas (main demand for lighting, radio and mobile phone, monthly demand usually below 20 kWh), the expansion of national networks in rural areas is often neither financially viable in the short term nor economically viable. Island networks are an alternative to network expansion . A distinction is made between isolated house systems ("solar home systems", usually operated with direct current) and smaller alternating voltage networks, which are characterized by a central energy supply with a local distribution system. Renewable energies such as solar energy , combined with diesel generators or solar batteries , often also old car batteries , serve as primary energy .

Electrification of railway lines

Electrification of the Ferrocarril General Roca in Argentina (2015)
Heideweek (2007)

Electrification is the name given to the conversion of a railway line from operation with steam or diesel traction vehicles to operation with electric traction vehicles with external power supply. The visible external sign is the attachment of the overhead line or conductor rail for the power supply.

In the case of traction current systems that require a separate supply of traction current, traction power stations, substations or converter stations must be built.

Historical development

The first electrically operated full-line railway in Germany was the 4.3 km long Meckenbeuren – Tettnang line in 1895 , which branches off from the Württemberg Southern Railway . In the same year, the Baltimore & Ohio Railroad electrified a five-kilometer-long inner-city tunnel in the United States for operation with 700 volts direct current over an overhead line.

In 1902 the first high-voltage three-phase current railway was put into operation in Wöllersdorf in Lower Austria , and in 1904 the first high-voltage alternating current railway in the world was put into operation in the Stubai Valley in Tyrol.

At the end of 2017, around 60 percent of the Deutsche Bahn network was electrified. According to the German government, the aim is to achieve a degree of electrification of 70 percent.


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  • Hendrik Ehrhardt, Thomas Kroll : Energy in modern society: contemporary historical perspectives . Vandenhoeck & Ruprecht, Göttingen 2012, ISBN 978-3-525-30030-5 .
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Web links

Commons : Electrification  - collection of images, videos and audio files

Individual evidence

  1. In: die Woche , Volume 21, Issue 1/1919, p. 33.
  2. a b c G. Dettmar, K. Humburg: The development of heavy current technology in Germany. Part 2: From 1890 to 1920 (= history of electrical engineering, 9), vde-Verlag, 1991, ISBN 3-8007-1699-2 .
  3. a b The Jablochkoff Candle. Online exhibition on arc lamps of the IET (English) ( Memento of the original from September 7, 2008 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. , The Institution of Engineering and Technology, England @1@ 2Template: Webachiv / IABot / www.theiet.org
  4. American History via Joseph Wilson Swan
  5. ^ TP Hughes: The Electrification of America: The System Builders. In: Technology and Culture , Vol. 20, Issue 1/1979, pp. 124-161.
  6. a b A. Riedler: Emil Rathenau and the becoming of the large economy. Berlin 1916. ( Online at archive.org )
  7. a b c W. Zängl: Germany's electricity: the politics of electrification from 1866 to today. Dissertation . Campus-Verlag, 1989, ISBN 3-593-34063-1 .
  8. ^ K. Wilkens: Die Berliner Elektricitäts-Werke at the beginning of 1907. In: Elektrotechnische Zeitung , 28 (1907), H. 40, pp. 959–963.
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  17. a b F. Niethammer: Single and multi-phase alternating current generator , Handbook of Electrical Engineering Vol. 4, Leipzig 1900
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  24. This problem can be visualized by feeding a bicycle dynamo with alternating voltage: Without an external impulse, the positive and opposing fields cancel each other out and at best a humming sound can be heard. Depending on the quality of the dynamo, it continues to run for a while in the direction of the impact after an impact, but stops immediately when loaded.
  25. H. Görges (Ed.): 50 Years of Electrotechnical Association. Festschrift, Berlin 1929.
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