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BELL SYSTEM TECHNICAL JOURNAL 



resistance is made twice its nominal value. This is well borne out by 

 Fig. 6 due to A. G. Landeen taken under conditions to which the 

 above discussion applies. 



LOAD RESISTANCE 



Fig. 6 



At first sight the result obtained, in which the secondary harmonic 

 current increases as the secondary resistance is increased for all values 

 of secondary resistance below twice the nominal secondary resistance, 

 seems a bit strange since the fundamental secondary current decreased 

 under the same conditions. A little thought however shows that the 

 increase of secondary resistance acts in two ways; first to reduce the 

 harmonic current directly, and second to increase the net magnetizing 

 force in the core which in turn increases the generated harmonic. 

 Thus with zero secondary resistance the net magnetizing force is zero 

 and no harmonic flux can be produced, while with large secondary 

 loads the flux density in the core or the net magnetizing force reaches 

 an asymptotic maximum so that the generated third harmonic increases 

 slowly if at all while the reduction in secondary current by the re- 

 sistance is continuously increasing. Under the assumptions noted 

 Equation (68) is valid for any circuit condition and it will be observed 

 that ig decreases with the primary resistance below the optimum point. 

 The value of a is explicitly 



a 02 I n\A 



a = 2.72 X 10- 



P'Li 



(72) 



