KR. BIRKELAND. M.-N. Kl. 



in some of the in parallel branches, its intensity will increase in the 

 remaining branches, until at last, perhaps, the entire original current is 

 broken in one branch with n breakers, in which case it is evident that 

 nothing has been gained by dividing the current into m branches. 



This contingency may be avoided by placing a coil with heavy 

 self-induction in each of the m branches, as shown by Elihu Thomson i. 



In the following pages, I am bringing forward a new method, by 

 which it will be ]5ossibic to break off suddenly a current of m ampères 

 and n volts, with a much smaller number of iireakers than m . «, if say 

 t ampere and i volt for each place of breaking be desired. l'or quickly- 

 moving interrupters, the circuit for the interrupted current may even be- 

 constantly continuous. 



The method consists in the introduction into the circuit of a vigorous 

 system of induction. This system, at the moment of breaking, induces 

 an electromotive counter-force in the circuit, far higher than the driving 

 tension, supposed to be n volts. This induced counter-tension may even 

 be made sufficiently great, and have a sufficient chance of operating, to 

 make the intensity of the current in the chief conductor exactly equal 

 to o at the moment of the opening of the circuit. If the current that 

 is to be broken is s ampères, the induced counter- tension E and the 

 time / for which E is allowed to act, must then be combined by the 

 equation: 



where R is the resistance, and L the coefficient of self-induction in the 

 entire circuit. 



Inducting systems such as this, and suitable for this purpo.se, may 

 be of various kinds. I shall now describe two or three of them. 



The inducting system may simply consist, for instance, of a hollow 

 coil, C, of large dmiensions, placed beside a large iron core, I, as shown 

 in the diagram, fig. i. Round this rorc may also be wound a few 

 layers of copper wire, through which jjasses a comparatively feeble 

 current, just sufficient to saturate the iron with magnetism. This previous 

 magnetising of the core is not, however, always necessary. 



The heavy core is supported in such a manner that it will slide 

 easily along a bar. A B, when attracted by the coil when the current 

 is passing through it. 



iii-oii's American patent of J.in. 171I1., 1893. 



