A dynamo or dynamo. It is an electric generator intended for the transformation of magnetic flux into electricity through the phenomenon of electromagnetic induction generating a continuous electric current


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  • 1 History
  • 2 Operation
  • 3 First models
    • 1 Pixii Dynamo.
    • 2 Dynamo of Pacinotti, 1860
    • 3 Little Dynamo Gramme, ca. 1878
    • 4 The dynamo in the car
  • 4 Common uses of dynamo
  • 5 Sources
  • 6 External links


During 1831 and 1832 , Michael Faraday discovered that a mechanical conductor moving in a magnetic field generated a potential difference. Taking advantage of this, he built the first electromagnetic generator , the Faraday disk , a homopolar generator , using a copper disk that rotated between the ends of a horseshoe- shaped magnet , generating a small direct current. It was also widely used as an electric power generator in bicycles to power light bulbs .


The current generated is produced when the magnetic field created by a magnet or a fixed electromagnet , inductor , passes through a coil , induced, placed in its center. The current induced in this rotating coil , in principle alternating, is transformed into direct current by means of the action of a rotating switch, integral with the armature, called a collector or switch, made up of electrodes called delgas . From here it is led to the outside by means of other fixed contacts called brushes that connect by rubbing with the collector’s delgas.

Early models

Dynamo from Pixii.

The dynamo was the first electric generator suitable for industrial use, as it was the first based on Faraday principles. It was built in 1832 by the French tool maker Hippolyte Pixii . It used a permanent magnet that rotated by means of a crank. This magnet was positioned so that its north and south poles passed by turning alongside an iron core with a coiled electrical wire like a core and coil.

Pixii discovered that the rotating magnet produced a pulse of current in the wire each time one of the poles passed by the coil; Each pole induced a current in the opposite direction, that is, an alternating current . Adding to the scheme an electrical switch located on the same axis of rotation of the magnet, Pixii converted the alternating current into direct current .

Dynamo of Pacinotti, 1860

In 1831 the first British generator appears, invented by Michael Faraday. In 1836 Hippolyte Pixii, a French instrument maker, based on Faraday’s principles , built the first dynamo, called Pixii’s dynamo. For this, a permanent magnet was used that was rotated by a crank. The magnet was positioned so that its north and south poles were joined by a piece of iron wrapped with wire.

Then Pixii realized that the magnet produced an impulse of electric current in the cable every time one pole of the coil passed. To convert alternating current to direct current, he devised a collector that was a metal partition on the cylinder axis, with two metal contacts. In 1860 Antonio Pacinotti , an Italian scientist, devised another solution to the problem of alternating current.

In 1871 Zénobe designed the first commercial power plant plant, operating in Paris in the 1870s . One of its advantages was to devise a better path for magnetic flux, filling the space occupied by the magnetic field with strong iron cores and minimizing the differences between still air and rotating parts. The result was the first dynamo as a machine to generate commercial amounts of energy for the industry .

Little Dynamo Gramme, ca. 1878

The Faraday and Pixii designs suffered from the same problem: they induced sudden spikes in current only when the north or south poles of the magnet passed close to the coil ; most of the time they did not generate anything.

Antonio Pacinotti, an Italian scientist, solved this by replacing the rotating coil with a toroidal coil , coiled in a ring- shaped piece of iron . Thus there was always a part of the coil magnetically influenced by the magnets, softening the current.

Later, Gramme reinvented the design by designing the first large-scale commercial generators, operating in Paris around 1870 . Its design is known as the Gramme dynamo. In 1870 he patented the theory of the magneto-electric machine to produce direct current. Since then new versions have been made with improvements, but the basic concept of endless rotating loop remains in all modern dynamos.

The dynamo in the car

One of the most common uses of the dynamo was as an electric power generator for the car . As automobiles became more complex since the beginning of the 20th century , the available electrical power generation systems (mainly magnets) proved to be insufficiently powerful for the vehicle’s needs . This circumstance favored the gradual implantation of the dynamo in it.

Although it was an element that provided the necessary energy with relatively little weight, it presented certain problems. The most important was that the speed of rotation that was supplied to it was never constant, since the revolutions of the motor are continuously varying, being the requirement that it had to be able to supply the same current at idle , slow movement, even when the motor was in full swing.

This was solved with the regulators that, although they are simple in their design, require a very delicate adjustment. These devices must be capable of regulating voltage and intensity. In addition, it should prevent the dynamo from operating as an electric motor when the vehicle is idling, which is when it produces virtually no power, so that the current flow is not reversed.

Since the dynamos have a design very similar to that of the electric motors, in the car they came to function as such when the current flow was reversed as the potential supplied by the battery was greater than the potential supplied by the dynamo.

Since the 1970s they have been progressively replaced by the alternator , and no vehicle is currently in production with this system. The generated current is produced when the magnetic field created by a magnet or a fixed electromagnet, inductor, passes through a coil, induced, placed in its center. The current induced in this rotating coil, in principle alternating, is transformed into direct by means of the action of a rotating switch, integral with the armature, called a collector, made up of electrodes called delgas. From here it is led to the outside by means of other fixed contacts called brushes that connect by rubbing with the collector’s delgas.

Common uses of dynamo

One of the main uses of the dynamo is the use of hydroelectric energy, in this way the water rotates the turbines connected to the dynamo axis, producing electricity and taking advantage of this inexhaustible source of energy.

They have been widely used by cyclists for years. Thanks to the dynamo, which generates electrical energy, cyclists have been able to circulate on the road at night with minimal lighting. In reality, the so-called bicycle dynamos are alternators; since they consist of a magnet, integral to the axis of rotation, and a static coil, without thin lines or brushes , that rectify the current. The current thus produced is alternate and not continuous, despite this, traditionally, they have been called dynamos. The end of the dynamo axle carries a head that is supported at will on the tire of one of the wheels, so that when turning the wheel, the dynamo turns.

The system is quite rudimentary and produces an appreciable friction that forces you to pedal hard . Because of this and the recent emergence of modern lighting systems with batteries of lithium lamps and LEDs , high power and autonomy , currently dynamos bicycle are deprecated.


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