HARMONIC PRODUCTION IN MAGNETIC MATERIALS 



777 



If MILS 



Fig. 45 



The experimental method for obtaining this result — the impedance to 

 a small third harmonic in the presence of a relatively large funda- 

 mental — is illustrated in Fig. 5. The method consists in measuring 

 the third harmonic current by means of a current analyzer ^^ for a 

 number of circuit conditions in which the fundamental current is 



TO CURRENT 

 ANALYZER 



'HIGH Z OUTSIDE BAND 



Fig. 5 



maintained constant. The circuit is first tuned to the third harmonic 

 by varying the capacity C in the third harmonic circuit, and the current 

 is then measured for a series of values of the series resistance r. A 

 shunt resonant circuit tuned to the fundamental is inserted in the 

 third harmonic path so as to separate effectively the third harmonic 

 circuit from that of the fundamental. With this precaution taken to 

 avoid harmonic production in the analyzer and to maintain the funda- 

 mental current constant while r and C are varied, the inductance 

 to the third harmonic is obtained from the resonating capacity, and the 

 resistance is determined as that value of r for which the third harmonic 

 current falls to half its maximum. 



^- For details of current analysis see the paper by A. G. Landeen, B. S. T. J., 

 April 1927. 



