180 



THE BELL SYSTEM TECHNICAL JOURNAL, JANUARY 1954 



stant velocity. This is because the decreasing magnetic pull (called drag 

 for the release case) has become small and the contact spring load is 

 dropped by the motion. The further forces acting on the armature then 

 are only the back tension and the difference between the rapidly de- 

 creasing contact spring load and magnetic drag. 



Returning now to equation (37) above, the release time is directly 

 proportional to the sum of the conductances, and to the difference be- 

 tween the saturation and residual fluxes. The conductance variations 

 can be determined from temperature, winding data, sleeve dimensions, , 

 and material. The saturation flux is directly proportional to the core 



1000 

 800 



600 

 500 

 400 



300 



5 100 



1 



10 20 30 40 50 60 80 100 200 300 4C 



RELEASE NI IN AMPERE TURNS 



Fig. 14 — Release time with a shunted winding. 



