THE DTK HI T-(t Hi; KM .MOTOR d[. VI 



tions in the ratio of the value of M at this load to its value 

 at no load. 



Let us now compare the efficiency curves of two 

 motors A and I ! which have the same internal 

 resistance and work on the same tension, but 

 have different induction curves. Suppose that for 

 equal currents the values of HI for A are greater than 

 those for B. 



If the torque losses are the same in both motors we 

 notice first that the curve of total efficiency for A cuts ih<- 

 axis of current nearer to the origin than does that of motor 

 B, since for the same torque the motor with the greater 

 induction factor takes the smaller current. A will thus 

 give a higher efficiency with light loads than B. 



Looking now at the equation for the greatest efficiency, 

 we see that for any current c f is greater for B than 



for A, and 2 /y/ / must be greater than ~w f , hence the 



maximum efficiency for B must be less than that for A. It 

 follows that the motor with the higher induction curve 

 has the greater maximum efficiency, and the greater 

 mechanical efficiency at all loads. 



Again, from Equation 58 we see that the current 

 when the efficiency is highest increases with c f . Hence the 

 point of maximum efficiency for the motor with the lower 

 induction curve will be shifted along the current axis, and 

 the maximum efficiency for the motor with the higher 

 induction curve will be reached at a smaller load than for 

 the motor with the lower induction curve. 



In Fig. 23 speed an.d torque curves were given for two 

 motors of equal resistance, but with different induction 

 curves. When the torque is large A runs quicker than 



