Pupin — Resonance Analysis of Alternating Currents. 483 



experiments just described the resonant current is then con- 

 fined entirely to the alternator and the line, the di-electric 

 forming a part of its circuit. These observations will be modi- 

 fied in the case of transformers with open magnetic circuits 

 and their equivalents, that is, closed magnetic circuits possess- 

 ing considerable magnetic leakage, especially when the condi- 

 tions of the line favor resonance with the fundamental fre- 

 quency, this frequency being low ; such magnetic circuits 

 possess much less magnetic sluggishness and can influence con- 

 siderably the conditions of resonance with a low frequency. 



VI. Distortion of the secondary current. 



It was pointed out that the superposition of harmonics upon 

 the fundamental wave was confined to the primary circuit 

 when the secondary is closed by a non-self-inductive resistance, 

 that is, if the transformer is of closed magnetic circuit type. 

 With an open magnetic circuit transformer the deviation of 

 the primary current wave from the simple harmonic form, due 

 to action of the generator or the transformer or both, is felt 

 more or less in the secondary circuit also. If, however, the 

 secondary is closed by a ferric self-inductance then odd har- 

 monics will appear in this circuit also in both types of trans- 

 formers. In fact, the secondary circuit should now, as far as 

 the harmonics are concerned, he considered as a separate cir- 

 cuit, in which the secondary coil of the transformer and the 

 ferric inductance in the secondary circuit play the same part 

 as the armature of the alternator and the transformer in the 

 primary circuit. 



The series of experiments which related to the origin and 

 growth of harmonics in the secondary circuit was similar to 

 the one described above, by means of which the so-called dis- 

 tortion of the primary current was studied. The results were 

 similar. The presence of harmonics is due to the action of the 

 ferric inductance ; their strength increases proportionally to the 

 intensity of magnetization of the iron in the ferric inductance. 

 They seem to be entirely independent of hysteresis, that is, if 

 by hysteresis the process be understood by means of which 

 most of the heat is generated in a very finely laminated, well 

 insulated and well annealed iron core, when such a core is sub- 

 jected to rapid reversals of magnetism. I shall describe briefly 

 an experiment bearing upon this point. The secondary circuit 

 of the five K. W. transformer was closed by an electrolyte resis- 

 tance, and a short cylindrical coil having about 120 turns coarse 

 copper wire. A short cylindrical core made up of very fine (No. 

 26 B. and S.), and well annealed iron wire could be inserted into 

 this coil. The core was 40 cm high and 5 cm in diameter. The 



Am. Jour. Sol— Third Series, Vol. XLVIII, No. 288.— Dec, 1894. 

 31 



