THREE-PHASE CURRENT MOTOR. 



The induction in the iron above the teeth should be no higher than 

 3000; this gives 15.0 cm of iron above the slots. 



The main dimensions of the motor are inscribed in Fig. 23. 



The resistance of each phase of the field is 0.28 ohm, hot 



The resistance of each phase of the armature is 0.016 ohm, hot 



The loss through hysteresis and eddy currents is noo watts, of 

 which 530 watts is dissipated in the iron ring, and 570 watts in the 

 teeth. 



82. We are now in possession of all the data necessary to predeter- 

 mine the behavior of the motor under load and at starting. 



This has been done in the following table. After the explanation 

 given in the preceding chapters, it would be superfluous here to enter 



FIG. 24. 



upon the manner in which these figures were derived partly from 

 Fig. 24, partly from the foregoing formulas. A word, however, has 

 to be said about the way in which the loss by friction is taken into 

 account With sufficient accuracy we may assume that the torque 

 necessary to overcome the friction is constant at different speeds. 

 By drawing a line parallel to the basis upon which the semi-circle is 

 described, we find in the length of the ordinates lying between this 

 line and the curve which lies next to the semi-circle in Fig. 24, a 



47 



