Magnetic Hysteresis loss in Straight Iron Strips. 2G3 



the determined hysteresis loss in the iron sheet, in watts per 

 pound per 100 frequency, at a maximum induction during 

 the cycle of 2500 C.Gr.S. units. Two processes are in 

 ordinary use for effecting this measurement. The most 

 accurate but most tedious is by the employment of a ballistic 

 galvanometer and the graphical delineation of a number of 

 (B, H,) cycles. This method has the advantage that it can 

 be conducted with either small or large samples of iron, 

 but the reduction of the observations to give the required 

 hysteresis loss is very tedious ; and including the construction 

 of the necessary ring-coil, the actual observations, and the 

 reductions, a single determination of the hysteresis value of 

 an iron can hardly be carried out, even by a couple of 

 industrious workers, in less than a day. 



The method employed by Professor Ewing and Mr. F. 

 Holden of rotating a laminated specimen of the iron in a 

 magnetic field, or rotating a field round the specimen and 

 comparing the torque produced on the field-magnet or on 

 the specimen with that produced by a similar sample of iron 

 of known hysteretic value or else measuring it by a calibrated 

 torsion spring, is very much more rapid. This last method 

 is, however, open to the great objection that if used merely 

 to compare a sample of iron with a standard sample, the user 

 of the instrument is at the mercy of his instrument-maker. 

 He receives with it one or more samples of iron which he is told 

 have certain hysteretic values, but he cannot check the truth 

 of the statement. Moreover, if he happens mechanically to 

 injure the standard samples he may seriously change their 

 hysteresis constant. The writer therefore sought for a 

 method which should combine the advantages of both the 

 above processes whilst eliminating their disadvantages, and 

 which should be an absolute method, like the ballistic method, 

 but at the same time a rapid method like the rotating-field 

 method. 



The following paper contains a description of a process 

 which is based upon the use of the bifilar reflecting wattmeter 

 and operates upon samples of iron, large or small, in the 

 form of straight strips which are simply slipped into a long 

 magnetizing coil. All the actual practical work and the 

 numerous calculations involved in putting this process to test 

 have been conducted under the author's direction by Mr. A. 

 R. Peart and Mr. W. M. Park working in the Electrical 

 Laboratory of University College, London ; and to these 

 gentlemen belongs the full credit for all this portion of the 

 research as well as for the labour required in much tedious 

 numerical and graphical work. 



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