4:82 JPitpin — Resonance Analysis of Alternating Currents. 



D, A, can be treated as an entirely separate circuit from the 

 circuit A, a' b', B, A. 



This statement needs practically no modification in order to 

 cover that case also in which the self-inductance of the pri- 

 mary of B is diminished by putting a non-self-inductive load 

 on the secondary. This utter disagreement between theory 

 and experiment deserves a closer discussion, but since its con- 

 nection with the subject of this paper is only an indirect one 

 I prefer to reserve it for some other time. That which has a 

 direct bearing upon the present discussion is the method which 

 the above mentioned relation offers for observing the variation 

 of the harmonics with the load without the disturbing induc- 

 tive effect of the large primary current. It is this : Connect 

 the air-core transformer a b (and with it the resonator) in 

 series with the condenser. Add to this series an auxiliary coil 

 c (no iron core). By the combination, thus obtained, bridge 

 the primary circuit, so that in place of the simple condenser 

 bridge D given in fig. 7 there will be a bridge consisting of 

 condenser D, the air-core transformer a b and the auxiliary 

 inertia coil c. The secondary C being open, tune the circuit 

 consisting of the alternator armature, the primary conductors 

 up to the bridge, and the bridge, to any one of the harmonics. 

 The tuning is done by means of varying the capacity of the 

 condenser and the self-inductance of the auxiliary inertia coil. 

 Then close the secondary circuit by means of an electrolyte 

 resistance and vary the secondary current. It will be found 

 that the harmonic diminishes only slightly with the increase of 

 the secondary load. As an example I give the following : 

 The circuit just mentioned was tuned to the harmonic of five 

 times the frequency of the fundamental, that is 650 p. p. s. 

 At no load the resonator indicated a rise of 108 volts, at over- 

 load (56 amperes) the rise was 94 volts. But this drop was in 

 all probability caused by armature reaction. 



Whatever the ultimate meaning of the appearance and the 

 persistence of the odd harmonics in an alternating current 

 wave may be I am not quite prepared to state with any high 

 degree of confidence. One thing is certain and that is that 

 they are at present at all loads with almost constant strength. 

 Their presence is hidden by the fundamental wave at large 

 loads, but when conditions favoring resonance with any one of 

 them arise they will certainly come out and do all the mischief 

 they can to the insulation. The self-induction of a motor or 

 that of a closed magnetic circuit transformer does not neces- 

 sarily affect the conditions of their resonance. These condi- 

 tions may depend in such circuits solely upon the self-induction 

 of the alternator on the one hand and the self-induction and 

 static capacity of the line on the other. According to the 



