BALANCED POLAR MERCURY CONTACT RELAY 



i4o; 



The magnetic pull on the armature in a gap of this kind is 



^ 980 ^"^ '''^ g^ (124.9) ^^ ^*^ 



where / is the force in grams g is the gap length and M is the MMF in 

 jDractical ampere turns across the gap. 



In the structure shown, therefore, the net force on the armature from 

 the gaps on both sides is 



J m — 



(124.9)2 L 



(A - ly 



% + ^y J' 



(Ms- 



(2) 



where the values of M are expressed in ampere turns. 

 If Mn = Ms this can be converted to 



fml 



L('-^)" 



(-01 



(3) 



where /„; 



\124.9/ 



Fiff. 12 shows curves of ^ versus - for various values of —=^ . Only 



^ fml h Mn ' 



one quadrant is shown as the system is symmetrical. It provides a con- 

 venient means for analysis of this type of relay. 



Fig. 11 — Simplified representation of relay. 



