II -KM M'ii'.\ :;:; 



largo and / small, Imth lmvin<_ r nn fjiial area in the 

 diagram. 



We have now tu inquire what determines the speed 

 when the load is fixed. If we put M m liquation 



1 _'. .". being the revolutiona per second. we get 



_/'- 



.................. ( l 



whii-li we see that when A'. /' and M are fixed, tin* 

 peed dependit only upon ; hut depends upon the load. 

 the speed depends on the load 



less than A'. / is positive. If the load is nothing 



- nothing and >. = ' so that if we had no load and 



no frictional or other resistance to oppose the motion, the 

 armature would run at a speed given by dividing the 

 tension of the line by the induction factor : tin- is there- 

 fore the maximum possible speed of a motor. If cR 

 n is nothing. Thi* is simply a different way of stating 

 the fact that if the current is a maximum, the speed in 

 nothing. 



\\ can also exprees the speed thus : 



il: 

 /1== -- ............... 



Example 12. l..t / =1"" V^^and /,'=_ 

 maximum Current in .',u .tin|-rt < ; mot :dy possible 



if the load is less than ><>l mcli-|...:. ippnee that 



the load is 300 inch-|M>untls, the current ref|uired to 

 balance the load is 26*6 amperes and the heat drop is 

 58*2 volU; the speed is thus 351 r.p.m. The maximum 

 possible speed for no load i* 7"><> r.|> m 



11 lv|uation I-', we see that when -itr. 



D 



