CHAPTER IV. 



The Leakage Factor. 



THERE are two questions of the most vital interest which in- 

 trude themselves at every step upon the designer. The first is, 

 How does the maximum output a polyphase motor is capable 

 of yielding, depend upon the air-gap? In other words, if I increase 

 the air-gap, does this to any great extent decrease the output? And 

 does a decreased air-gap increase the output of the motor? The 

 second question is this, If a motor is wound for four poles, and we 

 want to wind it for eight poles, provided the frequency and the in- 

 duction in the air-gap remain the same, does the output decrease in 

 the ratio of 4 -=- 8, or, what relation exists between the maximum out- 

 put of the motor and the number of poles? I shall now proceed to 

 answer these questions. 



THE INFLUENCE OF THE AIR-GAP UPON THE LEAKAGE FACTOR. 



39. In order to determine the interdependence between the magnetic 

 reluctance of the main field and the leakage factor, the following ex- 

 periment was made : The magnetic field the stator of a three-phase 

 current motor was provided with two armatures, the diameters of 

 which were so chosen as to create an air-gap of 0.5 mm, and one of 1.5 

 mm. The magnetizing currents were then measured as well as the 

 short-circuit currents. The following tables contain the results of 

 the experiment : 



Currents at 50 



