Seite - 43 - in Nikola Tesla and the Graz Tech

43 • Heinrich Rudolf Hertz (1857 – 1894): German physicist who in 1886 became the first person to prove and produce electromagnetic waves. He thus pro- vided the basis for the development of wireless telegraphy and the radio. • Guglielmo Marconi (1874 – 1937): An Italian pioneer of telegraphy who man- aged to carry out a wireless connection from Dover to Wimereux across the English Channel in 1899. In 1902, the first transatlantic wireless trans- mission was carried out, and in 1909, Marconi was awarded the Nobel Prize for physics. Tesla was granted more than 110 patents in America alone. He was awarded twelve honorary doctorates and is only one of twenty four scientists world- wide to have been given the honour of having his name used as a scientific unit: Volt, Ampere, Ohm, Hertz …and Tesla /1/. Since 1960, the ‘Tesla’ unit of measurement has designated the magnetic flux density in recognition of his outstanding scientific ideas and achievements. Associated with the natural magnetic field of the Earth, Tesla is thus immortalised all over the world. Tesla’s intensive research activities were triggered off by a disputation with physics professor Jakob Pöschl during a demonstration of a Gramme machine at the College of Technology in 1878. Prof. Pöschl had snubbed Tesla by call- ing a suggestion of his an impossible idea. Tesla had correctly identified the stream of sparks emanating from the two brushes on the commutator of the Gramme machine – necessary for direct current operation – as a source of great loss. His suggestion to Professor Pöschl was to dismantle the com- mutator and the sliding contact and to run the machine using alternating current /2/. In 1882, as the leading engineer of a telegraph company in Budapest, Tesla developed the idea of a rotating magnetic field that could drive a commu- tator-free motor. The genius of this idea was to produce the rotating mag- netic field by superimposing several out-of-phase alternating currents. The rotating magnetic field he invented brought his endeavours of many years to develop a powerful commutator-free alternating current motor to a success- ful close. Tesla built one of his first models of a motor driven by polyphase alternating current in 1893. The problem of the commutator The rotating magnetic field: Polyphase alternating current system