Wireless Transmission of Energy - Dream or Possibility Page 28

From unpublished manuscripts from Long Island

One of Tesla’s marked characteristics as an inventor and scientist was an unusual imagination and great freedom in expressing his ideas. Tesla could not be called a timid herald of new ideas and assumptions about what comes with the development of science and technology. Tesla stated his visions of the future publicly, and his self-confidence, often exclusiveness and uncompromising advocacy of his own views, sprang from the depth of his being. Tesla firmly believed in natural laws and in their existence. He believed that he himself took part in discovering the secrets of nature and its harmony. For himself he worked out special models, sometimes analogies of mechanical, hydraulic and electrical phenomena, and sought the laws that govern these fields. He had a feeling for the unknown in the natural sciences and a sense for finding solutions. Of all the challenges of the unknown, the system for the wireless transmission of energy was probably the one that troubled him most. It can almost be said that he spent half his life and working life searching for the solution of such a system.

The study of Tesla’s ideas on wireless transmission is exceptionally complicated even for a modern electrical engineer. One can only imagine how his contemporaries were able to understand Tesla! In the text that follows we shall try to give an explanation of Tesla’s model of wireless transmission and of his approach to modeling the propagation of radio waves in the region of very low frequencies, where Tesla expected that the realization of his idea was possible.

First ideas on the wireless transmission of electrical energy

The wireless transmission of electrical energy began to occupy Tesla’s attention at the beginning of the 1890s. From then on this idea did not leave him until the end of his life. It all began with the study of alternating currents of higher frequencies than those used in electric power for driving motors and for other applications in industry and the household.

We follow the evolution of Tesla’s idea of the technical basis for realizing a system for the wireless transmission of electrical energy in “significant amounts” through his patents of 1891 and the lectures he delivered before the American Institute of Electrical Engineers in the same period. These were Tesla’s years of brilliant successes and growing fame. Ideas poured from Tesla like a torrent, and he shaped them into practical forms and served them up for use. Tesla’s induction motor set out on its long journey, and its end is not in sight even today! Then the world also saw the “Tesla coil,” the “Tesla oscillator,” or the “Tesla oscillator of high-frequency currents,” all names for the same device — a spark oscillator with the same type of transformer without iron and with little copper wire, but of great effect.

The Tesla transformer without iron

To this day the Tesla transformer without an iron core has been made in many different forms and sizes. Tesla himself worked out several specific forms of the secondary coil, which must be carefully constructed if it is to work successfully even at voltages of millions of volts. The secondaries of Tesla’s transformers were in the form of a cylinder, a cone, or a spiral. In the cylindrical coils he spaced the windings, especially at the top of the coil, so that there would be no breakdown between the turns.

The voltages at the ends of the secondaries of Tesla’s transformers became ever higher. In 1891 these voltages amounted to some hundred thousand volts, and the dimensions of the coils to a few tens of centimeters. In the lecture Tesla delivered in London and Paris in 1892 he showed the details of the construction of the high-frequency transformer, which then entered the university textbooks of the beginning of this century. He performed wonderful experiments with currents of high frequency and astonished the greatest experts of that time. It was then that the wireless transmission of energy began to take shape in Tesla’s published works. “Very high voltages are necessary,” Tesla maintained, and he strove to achieve them. He perfected spark gaps which, as ideal self-regulating elements of the oscillator, performed the work of breaking and establishing the process in Tesla’s oscillator. He constructed spark gaps with the spark interrupted by compressed air or a magnetic field, and to an astonishing degree he perfected mechanical interrupters with mercury and a special insulating layer of oil. The number of spark interruptions amounted to as many as 100,000 a second, so that the currents in the secondary of Tesla’s oscillator were almost ideal sinusoids.

Publication of the basic conception of radio

Tesla gradually worked out his system of wireless transmission and spoke of it in several famous lectures before the greatest