I 



ADDITIONS TO THE THEORY. SECOND APPLICATION 103 



The fundamental can alone produce useful power, because it is 

 known that energy cannot be produced by the action of an E.M.F. 

 until the current has the same frequency. Since the harmonic terms 

 ist only in one of the machines they will simply produce parasite 

 rrents therein which will increase the heating by resistance-loss with- 

 iut any useful result. 



It is known that the square of the effective current is equal to the 

 m of the squares of the effective currents of the component sinusoidals. 

 The heating produced separately by each of the harmonics will there- 

 fore be added to the principal heating. This effect makes itself readily 

 apparent in the V-curves by an increase in the minimum current; 

 rhich will be much greater than would be necessary to obtain the power 

 .ctually developed. This can easily be observed by means of a watt- 

 meter, which will indicate a real power no longer equal to, but really 

 lower than, the apparent power (product of the effective current by the 

 effective voltage). It cannot be possible that cos </> is lower than unity, 

 since the current is in phase, as we know, under these conditions. 



It can even happen, as noted by Bedell and Ryan (Bedell and Ryan, 

 Journal of Franklin Institute, Mar., 1895, Fig. 9), on a motor having 

 a strong third harmonic, that the V-curve breaks up into two branches, 

 one of which is normal, at high excitations, the other being parasite, 

 and very high at low excitations. Between these there is no stable 

 load possible, without adding a strong self-induction in series. The 

 author, who has himself observed similar phenemona (A. Blondel. 

 Electrotechnische Zeitschrift, April 25, 1895), attributes this favorable 

 effect of a large self-induction (an effect which is contrary to the theory 

 given on page 53) to the obliteration (throttling) of the harmonics, 

 which meet, in passing through the self-induction, a reactance that is 

 proportional to their own frequency. 



In the case where it is the generator which has a distorted E.M.F., 

 it can be eliminated, as M. Perot has shown (Perot, Comptes-Rendus, 

 6 Aug., 1900, p. 337), by connecting in parallel, on the line supplied 

 by this generator, a synchronous motor (or a converter) having a sinu- 

 soidal E.M.F. This apparatus, opposing no harmonic to those of the 

 generator, short-circuits them without reducing the principal sinu- 

 soidal. If, therefore, we take Z equal to the generator-impedance 

 (or that of the group of generators) and z equal to the motor-impe- 

 dance, the amplitude of the harmonics, at the terminals, will be 



rj 



substantially reduced to -= of their value on open circuit. Perot has 



Zj ~\~ Z 



