372 Report S.A.A. Advancement of Science. 



independent. The total power absorbed by the circuit is equal to the 

 sum of the powers of the two currents, i.e., 



P= Eili cos 01 + E2I2 cos (/)2, 



and the copper loss caused by the currents in the resistance R is equal 



to (1:^+1/) R. 



The author believes that the first polycyclic system was due to 

 Dr. F. Bedell, the connections of a three phase single phase system, 

 as invented by him, being shown in Fig. I. Here G3 and d repre- 

 sent three phase and single phase generators respectively, T3 and Ti 

 three and single phase transformers, M3 a three phase motor, and L 

 a lighting circuit. 



Suppose now that the currents of the different phases of G3 are 

 equal and follow sine laws, then points d and 02 will be of the same 

 potential, so that a single phase current may be introduced in these 

 points, passing through the varies circuits as if no other currents 

 were present. The direction of the superposed current only is indicated 

 by the arrows. 



A single phase current may be superposed not only upon three 

 phase, but also upon two phase or another single phase currents. 

 The latter is then considered a two phase current with phases at 

 180 degrees, see Fig. 2. 



Bedell's system has the disadvantage that the superposed cur- 

 rents are carried by the primary system only, and that, since the 

 circuits of the superposed current are highly inductive, the pressure 

 drop is enormous. 



The latter disadvantage may easily be obviated by winding the 

 circuits noninductively for the superposed current without interfering 

 with the induction of the original currents. Consider the choking 

 coil as shown in Fig. 3, and assume that the superposed current 

 enters by bi and bs, leaving at e, while the original current enters at 

 bi and leaves at b2 ; it is obvious that the inductive action of the 

 superposed current is nil, since the flux caused by one coil is neutral- 

 ised by that set up by the other on the same limb, whereas the 

 inductive actions of the original currents are added. Such bifilar 

 windings may be given to all kinds of polyphase transformers and 

 generators, as illustrated in Figs. 4 and 5. The former illustrates a 

 three phase transformer, the latter a three phase generator or motor. 



Arnold-Bragstad-la Cour, the inventors of this system, have 

 further shown that superposed currents may not only be conducted by 

 means of transformers, but also be induced by them. The principle 

 of this new method consists of the simultaneous transformation and 

 supply of alternating currents of different phases and frequencies 

 into the mains of a distributing network by employing transformers 

 with two kinds of primary and one secondary windings, and by taking; 

 off these currents by means of one primary and two secondaries. 



