History of the Transformer

by Friedrich Uppenborn

Fig. 15.

We do not find in Gordon’s patent the slightest indication which would justify us in ascribing to him the invention of a system of distribution by transformers as known at the present day, but, on the contrary, it is clearly shown that the fundamental conditions of such a system of distribution were unknown to him, for he laid the chief weight upon connecting the induction coils in series, and on the production of high electromotive force necessary for his lamp. Over and above this, he was of opinion, as he stated prominently, that the more advantageous kind of dynamo was one such as that of de Meritens, having many coils of thin wire, which were connected to separately insulated leads.

Let us look back upon the inventions which were made in the domain of electric lighting by transformers from the time of Faraday’s discovery of induction up to the year 1880. There we see that three distinct characteristics were possessed by all the systems invented up to that year. These three characteristics lay in the construction, the ratio of transformation, and the method of employing the transformers. Single transformers, with two or more poles, were used. The ratio was either 1:1, in which case the induction coil is really not a transformer, or it was from a low to a high electromotive force; but nowhere do we find that currents of high electromotive force were converted into those of low electromotive force. The idea in the use of transformers was that of division, not that of distribution of electric energy. The difference between division and distribution of electrical energy is, in the main, as follows. By a division of electrical energy it is meant that a fixed amount of produced energy is divided into pre-determined parts of a certain number and size, while it remains indifferent, as far as the total energy is concerned, in what manner and how many of these parts are usefully employed. By distribution of electrical energy it is meant, on the other hand, that the energy produced is variable according to the variable requirements of consumption, the maximum requirement being pre-determined from the number and size of the local requirements, which also vary relatively to one another. Of the last of these systems there is no indication in any of the inventions of induction coils up to this date.

If we seek for the cause of these characteristics, we find that the reason why transformers with two or more poles were constructed is, that the electricians of those days either did not know or did not understand the principles on which a proper transformer should be constructed. With them the idea of a magnetic pole acting on a wire near it was always present, while they entirely overlooked the fact that the electro-magnetic force, not the pole, produced the electromotive force in the wire. On account of this they were of opinion that free poles in a transformer were not only not a drawback, but, on the other hand, a distinct advantage.

We find that Fuller especially held this view. He sought not only to have in his apparatus two simple poles, but double poles, and indeed he patented this arrangement of his transformer. The first claim of his patent reads thus:—

“The double electro-magnet herein described, the main coils of which are included in the circuit of a main conductor from a generator of alternating electric currents, producing in said magnet consequent magnetic poles, as shown, and around which poles are coiled helices of wire for receiving the currents induced by the polar changes, said helices being included in the local circuit with the lamp.”

We must bear in mind that, as far as the ratio and idea of employment of a transformer are concerned, the problem at that time was quite another to what it is now. At present the transformer serves principally to render possible the carrying of the current to a great distance economically. The electricians of those days were not so far advanced as to be able to run arc lamps independently of one another on the same circuit, and this they held to be quite impossible, whether the lamps were connected in parallel or series. That apparatus was thought to be good which allowed separately insulated currents to be led from one source of current, each separate circuit going to feed a single lamp. The chief reason for this view lay in the fact that the extinguishing of all the lamps in one circuit could easily take place through the fault of one of them. At that time, when an arc lamp was cut out of circuit, it was replaced by a fixed resistance, instead of which it was thought that induction coils would have suited well. It may be casually mentioned that owing to this fact too sanguine hopes of the solution of the problem of independent working of lamps were aroused, through a want of sufficient knowledge of the laws of induction. There have also been apparatus other than induction coils used for the purpose of making the points of consumption independent of one another. We can only now recall the patent of Jablochkoff, No. 1638, which is based on the principle of connecting condensers into branches of a quickly alternating main current, from which arc lamps, &c., were fed; also a like arrangement by Avernarius (Figs. 16 and 17), with the use of secondary batteries, which were to be employed for either parallel or series connection.[2]

Fig. 16.