/'/i\/(;.v cn.iR.ici i-.Hisrics or i.i.r.ci is-oM.tcxr.is 221 



riic slops by wliiili tin- sdliitlnn tilting tliOM- i-oiiditioiis an- i>l>iaiiioil 

 will not be given \nH tin- results, stated in pratticil units, are iinliidi'd 



Fig. 9 — Relation Between Coil Depth in Terms of Core Diameter and Effective 

 Operating .Ampere Turns 



to bring out certain important facts relating to winding design. The 

 final temperatures are 



K FT 

 Constant Wattage, T)= -^ [-20°; 



Constant Current, 7/ = 



A, 



5090/1 1 + 234. o/-/^;oA.'i 

 2b^.bAx-PR^i 



(10) 

 (11) 



I 2t4 FtK.F^ 

 Constant Voltage, r/= - 107 + * 16000 H ; „' ( 



12) 



The transient temperatures of constant wattage, voltage and current 

 are all of the exponential form T=Tm {l — (~"), while the cooling 

 f>f the winding after current is stopped is of the form T=T„ e~' . 

 In these equations c is the constant pertaining to the particular 

 condition considered. 



An important observation in connection with these temperature 

 characteristics is the great difference in temfxjraturc rise in the three 

 cases with like initial conditions of energy- input. Thus, it is important 

 to note that an electromagnet which is correctly designed and worked 



