48 



NOTES ON THE EFFECT OF HARMONICS ON THE TRANS- 

 MISSION OF POWER BY ALTERNATING CURRENTS 



[Electrical World, XX, 368, 1892; La Lumiere Electrique, XL VII, 42-44, 1893] 



In a recent number of The Johns Hopkins University Circular and 

 the Phil. Mag. for July, 1892, x I have shown that an iron transformer 

 introduces harmonics of the periods 3, 5, 7, etc./ times the fundamental 

 period into the currents and electromotive forces both primary and 

 secondary of a transformer and that these increased in value as the 

 iron was more and more magnetized. 



It is my present object to call attention to the effect of these har- 

 monics on the transmission of power and its measurement. For light- 

 ing purposes they are evidently of very little significance, as currents 

 of all periods are equally efficient in producing heat. There is a loss, 

 however, in the fact that they cause more loss of heat in the wires and 

 the iron of the transformers. But for the transmission of power the 

 case is very different. Here the motors are designed to run at speeds 

 dependent on the period; if there is more than one period the adjust- 

 ment fails, and there is a loss. The harmonics are thus useless in the 

 transmission of power by synchronous motors, and are of very little use 

 in motors with revolving fields. In these cases the harmonics travel 

 around the circuits, heating the wires and the iron without producing 

 valuable work. They then represent an almost complete loss in the 

 transmission of power, and as they may contain 10, 20 or even 30 or 40 

 per cent of the current, according to the magnetization of the trans- 

 former, they are probably responsible for some loss of efficiency in many 

 cases, as will be shown further on. 



Indeed, I believe they are the explanation of many seeming mysteries 

 in the working of alternating current motors. 



Special arrangements of condensers and coils can be made to pick 

 out these harmonics so that they become more important than the 



1 See also the Electrical World of July 9, 1892. 



2 The periods 2, 4, 6, etc., can evidently be introduced by magnetizing the iron of 

 the transformer in one direction by a constant current, or having it originally with 

 an asymmetrical magnetic set. 



