Discussion on magnetic properties of iron at frequencies up to 200,000 cycles. New York, November 13, 1911. (see proceedings for December, 1911)

1912 Proceedings of the American Institute of Electrical Engineers  
Harold Pender: I should like to call attention to the fact that the results of this paper are confirmed by some experiments which were performed at the Institute of Technology last year under my direction by F. B. Silsbee. The method used was entirely different. For the high frequency generator we used an arc giving a frequency something like.200,000 cycles per second. This frequency was impressed upon a primary winding on a small iron core made up of very fine iron wire, and the electromotive
more » ... the electromotive force induced in a secondary winding on the same core was measured. This secondary induced electromotive force was also calculated on the assumption that the true permeability is independent of the frequency. In making this calculation the proper allowance was made for the non-uniform distribution of the flux in the core, usually referred to as the magnetic skin effect. The measured and calculated electromotive forces were found to agree quite closely. B. A. Behrend: This paper is interesting in bringing again to our attention the question of high frequencies, a question which 20 years ago was perpetually under controversy. The paper of this evening is extremely instructive, although I regret that the able author does not strongly bring out the fact that, as far as fundamental laws and principles are concerned, the problem confronting the physicist or the electrical engineer, whether frequencies of 10 cycles, 25 cycles, 60 cycles, 120 cycles, or 100,000 cycles are involved, remains exactly where it was before; in other words, the permeability of iron as such remains unchanged independent of the frequency. This fact has, I be lieve, been known for some time. The high frequency induces vitiating factors which make it appear as" though the permea bility of iron were different for different frequencies, which it is not. There is another point in the paper on which I wish to comment and that is the point of efficiency of high frequency apparatus. The apparatus may have a high efficiency, as the author has stated, but the apparatus is useless in its present form for practical applications other than wireless telegraphy, because of its want of regulative properties; in other words, a transformer or a generator of high frequency, though its efficiency may be entirely satisfactory, is an inferior piece of apparatus, in fact, an impossible piece of apparatus for the operating conditions re quired by the use of current consuming devices of low power factor. The statement which I have made is of a certain measure of importance and of interest to those of us older men, who argued in former years strongly in favor of lower frequencies in order to be able to design satisfactorily transformers, generators, and motors. The higher efficiency of the high frequency transformer MAGNETIC PROPERTIES OF IRON [Nov. 1911] DISCUSSION AT NEW YORK 63
doi:10.1109/paiee.1912.6659496 fatcat:k6kgm2hvgjgjzbxrdlu6ldkvya