8 



KR. BIRKELAND. 



M.-N. Kl. 



which llie secondary currents endeavour to do it, if there is sufficient 

 time for tlie currents to become stationary. The primary current will 

 then, at each breaking, have to reserve the magnetism in the iron core, 

 without any previous commutation of the poles being necessary. 



We will now, as in the case first described, illustrate diagrammati- 

 cally the manner in which the various operations necessary for the 

 breaking of a current by this mctlfod, can be performed in a single act. 



F'S. 3- 



When the lever, h c, is raised, the current is forced to pass through 

 only the primary coil of the transformer. If the secondary current is closed 

 a moment before the contact at b' is broken, the transmission of the 

 main current from the conductor, a e, to the primary coil is facilitated 

 by induction, especially if the secondary cvirrent predominates over the 

 primary. While the lever, he, is being raised to its highest position, 

 the primary and secondary currents have time to increase to maximum, 

 after which they are broken by the release of a spring which quickly 

 raises the circular ebonite plate, E, with the numerous contacts. The 

 diagram, fig. 3, illustrates how the breaking takes place. 



When the lever, be, is raised, the ebonite plate is pressed down, 

 notwithstanding the spring, g, which endeavours to hold the plate up. 

 A moment bcftjrc the lever leaves the contact-pieces, b', all the contacts 

 // and fonE arc closed. Hy a revolver-mechanism, indicated in the figure, 

 the ebonite disc is released when the primary and secondary currents 

 in the transformer have had lime to rise. The spring, g, then draws 

 the ebonite plate quickly up, and the currents are broken, the primary 

 at the contact /, the secondary at ihc noumcrous contacts //. The 



