Heinrich Ruhmkorff's Spark-Coil

IEN Galileo Ferraris - Museum

Collection of Historical Electrical Instruments

The electrical researcher Heinrich D. Ruhmkorff, from Hannover, around the middle of the nineteenth century was able to improve Callan's two-winding induction spark-coils, on the basis of the research conducted in Paris by Masson and Breguet in 1842, in such a way that since then these devices bear his name.

Heinrich Ruhmkorff's Spark-Coil from the collection of the Museum of IEN Galileo Ferraris

Heinrich Ruhmkorff's Spark-Coil from the collection of the Museum of IEN Galileo Ferraris


The first patents date back to 1851 and follow one another introducing a few fundamental novelties. The iron core is still rectilinear and the primary winding, close to the iron, and the secondary winding, are arranged on it. The primary winding is fed by a storage battery, through a switch operated by the magnetized core. The current in the primary winding is pulsed, and the voltage on the secondary is alternating.

First of all, Ruhmkorff took particular care of the secondary insulation, using for the winding a lacquered copper wire, then inserting between one layer and the other a sheet of paper or varnished silk and finally separating the primary winding from the secondary one by a glass pipe.

Afterwards, by using an invention of the English E. and C. Bright, he divided the secondary winding into compartments, each one wound and insulated from the others; all were then connected in series. In this way the spots between which the highest difference in potential was to be found were at the greatest possible distance. The secondary wire could reach even tens of kilometers of total length.

Later Ruhmkorff improved the mercury switch by covering the mercury with alcohol to extinguish the spark and avoid oxidation. Finally, applying fizeau's device, he connected a capacitor between the terminals of the primary interruption bow, in order to increase the induced voltage. The frontal pawn is used to invert the primary current.

References

J. Fleming: The alternate current Transformer - "The Electrician" Company, London, 1892 - vol.II - p.35.

A. Ganot: Traité de Physique - Hachette, Paris, 1894 - p.1041.


Source: http://www.ien.it/museum/txt/rocch_ruhmkorff.html

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