150 



THE BELL SYSTEM TECHNICAL JOURNAL, JANUARY 1954 



the inductance at the open gap and at the critical load gap. These are 

 weighted in proportion to the ampere turns developed at each location. 

 The ampere turns necessary to overcome the back tension is one factor, 

 and the other is the difference between this first ^-alue, and the total 

 required for operation at the critical load gap. This weighting yields an 

 effective inductance value intermediate between the two extremes for 

 each problem, but a new chart does not have to be prepared. An operate 

 time using the chart is first determined. This time is then adjusted bj'' 

 the ratio of the effective inductance applying and the inductance used 

 for making up the chart. This is exact, as the inductance term appears 

 only as a direct multiplier. 



A typical nomogram is shown in Fig. 2. It already includes the motion 

 time correction, whose determination will be discussed. The dashed line 



x10^ 



4 5 6 8 10 



20 30 50 60 80 100 



TIME IN MILLISECONDS 



200 300 400 600 



Fig. 2. — Nomogram for solution of load controlled operate time. 



