ill IV -HfM-WolM. M..I, ,.. 



have been plotted in I'i^. 1'.' on a base of current in 

 th- nnnatii . method that will lie il.--ril>ed 



It tin- induction t-ictor remains constant, tli 

 will ditnini-h as tin- load increases. If we wish tin- speed 

 t<> remain constant, we tnu.-t arrange that the induction 

 factor shall vary o that tin- eH'.-ct <lue t<. the increased load 

 is counterbalanced. 



Mi>t<.r* are uMially worked under conditions when a 



as** of M involve- an increase of the speed ; when this 

 is so, we must arrange that M shall decrease with an 

 increase of the load. This we can <lo ly winding round 

 the magnets a circuit that shall carry the whole or part ..(' 



iiain current, to that a* this increases it shall produce * 

 a magnetisation of contrary sign to that of the shunt 

 win- !i*- motor i- then said to be compound 



wound, and the series winding, a* it i- called, acts in 

 op|Hition to the hunt winding. 



Example 24. \ motor with an internal resists 

 of (H3 ohm ha* to run at constant speed of 1. *<>> r p.m . 

 on a line of 12*> volts tension. T mni current is 



1 ami^n-H. At no load tin- induction fa-tir has to b- 

 whd at full la<l it has to be 1 J-. It w,- ha\e th- in- 

 duction curv.-, :md know the number of turns in the shunt 

 win*: can at once tee how many turns carrying the 



maxim t are required to reduce M to its proper 



value at full load. If the induct ion curve U straight 

 between the maximum and minimum values of I/, tic- 

 speed will be constant at all load*. It ax i* usually the 

 case, it is concave to tb- udi, */ will U- t.K, high 



MH-ilium load- ami th.- sjn-ed will consequently U too 

 low. 



r 



