# Zenobe grams

Zénobe Théophile Gramme

Zénobe Théophile Gramme (born April 4, 1826 in Liège , † January 20, 1901 in Bois-Colombes ) was a Belgian designer and inventor.

## Life

Gramme was a model maker in the workshops of the Compagnie l'Alliance . In 1871 he invented his ring fitting without knowing anything about Antonio Pacinotti's invention. This ring fitting is also known as the Gramme ring or the ring armature motor. He demonstrated his “Gramme machine”, a dynamo-electric motor with continuous induction , to scientists in Paris on July 17, 1871.

In 1888 he was awarded the Volta Prize . The Belgian training ship built in 1961 bears his name, as does the asteroid (2666) Gramme .

### Functional principle of the Gramme ring

Grammescher Ring

Let us imagine a rod that is composed of a number of magnets that butt with their poles of the same name. This rod is bent into a ring. The ring slides through an annular spiral made of copper wire. A simple consideration also tells us that when the ring is stationary and the wire coils rotate to the right in the direction indicated by the arrows, a total current is created in the left-hand half as well as in the right-hand half. These currents are strongest where the ring has its poles, i.e. at s and n , but they stop in the indifference zones o and w . However, we can combine the two currents into one if we create a line between the spiral turns that are currently above points o and w , which can best be carried out in such a way that we are directly on the wire turns at o and w drag two metal brushes −B and + B , which take up the current. If these two brushes are so wide that they take the current from the wire before it disappears, we get a continuous induction current, from + B via the connecting wire to -B , as indicated by the arrow. The device works just like a battery, the poles of which are at + B and –B . It is now clear that in this way it is very easy to generate strong continuous currents using strong electromagnets, since we know that the strength of the current depends on the strength of the magnet and the length of the wire wound on the turns .

### Pacinotti-Grammescher Ring

Pacinotti-Grammescher Ring

The arrangement we have chosen to explain the origin of this current cannot, however, be used in technology for the reason that the magnetic ring cannot be held in place. In the technique of Pacinotti's process, one helps oneself very simply in the way that one unites the ring with the wire spiral to a single solid whole and that one then lets the whole rotate between the poles of an electromagnet. The two poles s and n of the above illustration have been replaced by the poles S and N of the electromagnet. These induce the two magnetic poles n and s in the ring of soft iron rotating between them together with the wire spiral , the magnetism of which of course always remains in the same place if the ring itself continues to rotate. We can therefore regard these influential poles as two unchangeable fixed points over which the ring and the wire spiral wound on it slide continuously. It is these points that in turn continuously induce an electrical current in the wire spirals, in the manner as we have just described in detail. This current is conducted from each wire spiral to a cylinder C placed on the axis and taken there by the brushes + B and −B . The device that collects the current and combines the two currents of the right and left halves into a single uninterrupted current is called a commutator . The brushes that drag on it are called commutator brushes .

### DC generator

DC generator from Gramme which was exhibited at the World Exhibition in Vienna in 1873

The dynamo consists of a ring that is wound from iron wire. Wire spools made of copper wire sit on this ring. The beginning and end of the coil are soldered. About 60 to 100 such coils, which themselves have about 300 turns, sit on the ring. The soldered wire ends are all on the same side of the ring and are connected to a collector that sits on the wooden core (in the case of handheld machines) and also supports the ring anchor . This wooden core also forms the shaft of the dynamo. The resulting direct current is drawn from these collectors with the help of brushes . The magnetic poles are arranged opposite one another on both sides of the ring. A later practical machine was the type supérieur , in which the base plate, the axle bearings and the pole shoes are made from one casting.

One of the first applications of this generator was the galvanic metal precipitation, as this type of generator mainly delivered high currents at low voltage. It was first presented at the World Exhibition in Vienna in 1873 . The Berndorfer Metallwarenfabrik was the first company in Austria to use it to silver-plate cutlery .

### Alternator

Gramme also built an alternator , the Auto-Excitatrice . Radially arranged plate-shaped electromagnets are located on the shaft . The ring fitting is a solid, wide iron ring on which the wire coils are wound, the ends of the coils go alternately to the north or south side of the ring, unlike the direct current dynamo. The rotating electromagnets generated alternating currents. Such an alternator provides electrical power for eight Yablotschkow candles with a total power of approx. 11.8  kW (16  HP ). The generator weighed 650  kg , 103 kg of which was copper wire.

Its machines delivered a less periodically fluctuating current than the early machines, e.g. B. the Alliance machines of the Compagnie l'Alliance. Although they were less complicated than their predecessors, they were not perfect in their performance and no longer sufficed for the increasingly better devices, lightbulbs and arc lamps. And so Gramme shares the same fate of oblivion, like many other pioneers in early electricity history (such as Glücher , Friedrich von Hefner-Alteneck , Paul-Gustave Froment , Gustave Trouvé and others). For a while, the Grammesche Ring survived in physics and handicraft books for young people interested in technology as well as some models in schools and physics lecture halls. Its engines were gradually replaced by others and so they were forgotten by the 1930s. Ultimately, the motor / dynamo from Werner von Siemens prevailed .

## literature

• General and practical knowledge library for military candidates . tape III . German publishing house Bong & Co, Berlin a. a. 1905.
• Tichy, Gottfried: Zénobe Gramme: a search for clues . Aichmayr, Schwanenstadt 2009, ISBN 978-3-901722-14-1 .