21G THE BELL SYSTEM TECHNICAL JOURNAL, JANUARY 1954 



UjCC 



•^'^ 500 



^§ 



Z>- 400 

 — ui 



5< 



'^< 300 



uiO 

 </)-! 



.<,Q 



15 20 25 30 35 



AMPERE TURNS JUST HOLD OR RELEASE 



Fig. 15 — Engineering data for release time estimation. 



load attainable in all cases. This corresponds to the case in which the 

 contact force, which is not subject to adjustment, has its maximum 

 value. The NI value read from the hold curve for this load is the lowest 

 that can be specified as a "hold" requirement. Each individual relay has 

 a release F versus Nl characteristic intermediate between the release 

 and hold capability curves. To meet the hold requirement its load must 

 be adjusted, and this adjustment is subject to the tolerance cited above. 

 The minimum load is set by the hold requirement, and the maximum 

 load is set by a release requirement of a lower A^/ value, the difference 

 between the two iV/ requirements corresponding to the tolerance range 

 in load adjustment. 



Thus adjustment values are determined in the form of limits to the 

 ampere turn value at which release occurs: the lower limit is the release 

 value, the upper the hold. The release time limits can then be read from 

 the timing curves. The maximum time is read from the maximum curve 

 at the release ampere turn value. The minimum time is read from the 

 minimum curve at the hold ampere tiu'n value. This minimum time, 

 when determined for the largest sleeve, is the longest time that can be 

 guaranteed for the load in question, and is subject to reduction in service 

 by the temperature variation previously discussed. When a shorter re- 

 lease time is desired, a smaller sleeve may be used, or a higher hold 



