The Ewing High-Frequency Alternator And Parsons Steam Turbine

Date: 
Saturday, January 21, 1893
Volume: 
6
Pages: 
259-259
Archived Page: 
Author: 
Subject: 
Publication: 

January 21 1895 959 The Ewing High-Frequency Alternator and Parsons Steam Turbine. Mr. Nikola Tesla has sent the following interesting communication to the editor of the London Electrician : In your issue of November 18 I tind a description of Prof. Ewing’s high-frequency alternator, which has pleased me chteiiy because it conveyed to me the knowledge that he, and with him, no doubt, other sci- entitic men, is to investigate the properties of high~frequency currents. With appa. ratus such as you describe, shortly a num- ber of experimenters, more competent than myself, will be enabled to go over the ground as yet but imperfectly explored, which will undoubtedly result ln the ob- servation of novel facts and elimination of eventual errors. I hope it will not be interpreted as my wishing to detract anything from Prnt. Ewing’s merit if I stats the fact that for a considerable time past I have likewise thought of combining the identical steam turbine with a high-frequency alternator. Anch’ io sono pittore. I had a number of designs with such turbines, and would have certainly carried them out had the turbines been here easily and cheaply obtainable, and had my attention not been drawn in a different direction. As to the combination, to which you give a rather complicated name, I consider it an excellent one. The advantages of using a high speed turbine are especially great in connection with such alternators. When a belt ia used to drive, one must resort to extraordinarily large diameters in order to obtain the necessary speed, and this increases the dimculties and cost of construction in an entirely unreasor.» able proportion. In the machine used in my recent experiments the weight of the active parts is less than 50 pounds, but there is au additional weight of over 100 pounds in the supporting frame, which n very careful constructor would have proba- bly made much heavier. When running at its maximum speed, and with a proper capacity in the armature circuit, two and oue»half horse-power can he performed. The large diameter (30 inches), of course, has the advantage of aifordlng better facility for radiation; but,on the other hand, it is impossible to work with a very small clear- ance. I have observed with interest that Prof. Ewing has used a magnet with alternating poles. In my Hrst trials I expected to obtain the best results with a machine of the Mordey typwthat is, with one having pole projections of the same polarity. My idea was to energize the field up to the point of the maximum permeability of the iron and vary the induction around that point. But Ifound that with a very great number oi pole projections such a machine would not give good results, although with few projections, and with an armature without iron, as used by Mordey, the resultsohtained were excellent. Many experiences of simi- lar nature made in the course of my study demonstrate that the ordinary rules for the magnetic circuit do not hold good with hlghfrequency currents. In pondtrable matter magnetic permeability, and also specidc inductive capacity, must undergo considerable change when the frequency ls varied within wi e limits. This would render very difficult the exact determination of the energy dissipated in iron cores by very rapid cycles of magnetization, and of that in conductors and condensers, by very quick reversals of current. Much valuable work remains to be done in these fields, in which it is so easy to observe novel phe- nomeua_ but so ditiicult tomakequantitative determinations. The-results of Prof. Ewing’s systematical research will be awaited with great interest. It is gratifying to note from his tests that the turbines are being rapidly improved. Though Iam aware that the majority of engineers do not favor their adoption, du not hesitate to say that I believe in their success. I think their principal uses, in no distant future, will be in connection with alternate current motors, by means of which it is easy to obtain a-constant and, in any desired ratio, reduced speed. There are objections to their employment for driving direct current generators, as the commuta- tors must he a source of some loss and trouble. on account of the very great speed; but with an alternator there is no objection- able feature whatever. No matter how much one may he opposed to the introduc- tion of the turbine, he must have watches with surprise the development of this curl- ous branch of industry, in which Mr. Par- sons has been a pioneer, and everyone must wish him the success which his skill had deserved.

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