KCOXOMICS OK TKLKl'IIONK KKLAV A I'l'LICATIONS 223 



llien there is no doubt about designing such a new coil if its manufactur- 

 ing cost will increase b}^ only 20 cents. So the relay designer needs to 

 understand how various factors, from original manufaclure to hnal 

 application, may be stated on a cost basis that is comparable throughout. 

 Among the most important special cases are the following: 



1. Manufacturing cost of winding a coil, 



2. Manufacturing cost as a function of ainnial demand, 



3. Ecjuivalent manufacturing cost of power consumed by relays, 



4. E(iui\'alent manufacturing cost of functioning time of a relay. 

 The method of e\'aluating each on the same basis will now be briefly 

 outlined. In each case, it should be noted that since only comparisons be- 

 t ween variable portions of the system are considered, only incremental 

 ^'alues need be considered. 



1.1 THE COST OF A WINDING 



111 comparisons between coils, certain common operations, such as 

 soldering the leads, using and cementing spoolheads, etc., will always 

 subtract out, leaving only the difference due to varying amount of 

 copper, which is paid for by the pound, (or per ohm), and the number of 

 turns, which depends on the speed of the winding machine and number 

 of coils wound at one time. Thus, winding costs, which depend only on 

 the electrical design, may be considered as varying only with the cost 

 per ohm and cost per turn, as given in equation (1): 



Cir = CnR + CsN, (1) 



where Cw = total cost of the variable part of the winding, 



Cr = cost per ohm, which may be tabulated by wire size, 



Cjv = cost per turn of winding, also given in tables by wire size, 



R = resistance of coil, ohms, 



N = number of turns in winding. 



Typical \'alues of Cr and Cn for a particular kind of wire and coil are 



shown in Fig. 2. 



1.2 COST AS A FUNCTION OF ANNUAL DEMAND 



^"arious components of relays, as well as their assembly routines, 

 occur in several variants of a general basic pattern. In the course of their 

 manufacture it is necessary to stop the manufacture of one unit, reset 

 the machine, and proceed with manufacture of another. Whenever this 

 happens, pi'oduction stops; and work must be done to reset the machine, 

 all of which may be evaluated as a set-up cost (designated S). As more 



