THE INDUCTION MOTOR. 



of the alternating current transformer, and a successful design must 

 endeavor to keep a as small as possible. The determination of a will 

 be treated of in a chapter devoted entirely to the leakage factor. 



10. The following table contains the results of a series of measure- 

 ments as a corroboration of the theory. The data were taken from a 

 three-phase current motor, the armature of which was standing still ; the- 

 whole apparatus was thus acting as a transformer with considerable 

 leakage. The field contained 36 closed slots, 7 conductors in each slot ; 

 resistance of each phase 0.045 ohms. The armature contained 90 

 round holes, 3 conductors in each hole; resistance at each phase 

 0.172 ohms. Number of poles, 6. Frequency, 48 . 



1 1. A graphic representation of the experimental data of the table is 

 given in Fig 4. 



It will be noticed that the observed points lie very closely on a circle, 

 the diameter of which corresponds to 168 amperes primary current. 

 Below each point the primary and secondary currents are written, 

 the latter being taken from the diagram. The agreement between 

 them and the observed values in the table may be called satisfactory, 

 especially since we have had to guess as to the real value of v. 



12. From our table we can compute the value of v\. A voltage of 97.5 

 at the primary would, if there were leakage loss, produce at the sec- 

 ondary a voltage of (93 X 3 -T- 97 X 7) 97-5 = 104.5. We observed, 

 however, only 94, hence we have 



= -- = 0.90. 

 104.5 



