CHAPTER XII. 



THE INDUCTION MOTOR. 



123. The induction motor. The induction motor consists of a 

 primary member, to the windings of which polyphase * alternating 

 currents are supplied, and a secondary member with short-cir- 

 cuited windings. The primary member is generally stationary 

 and it is called the stator, and the secondary member generally 

 rotates and it is called the rotor. The stator windings are exactly 

 like the windings of a polyphase alternator armature, f the alter- 

 nating currents in these windings produce a rotating state of mag- 

 netism in the laminated iron of the stator, this rotating magnetism 

 induces currents in the short-cir- 

 cuited rotor windings, and the stator 

 magnetism exerts force on these 

 induced currents and causes the 

 rotor to revolve. 



The structure of the induction 

 motor is shown in Figs. 218 to 222, 

 which show the details of a small 

 motor manufactured by the West- 

 inghouse Electric Company. Fig- 

 ure 218 shows the cast iron frame 

 for holding the stator laminations, 

 Fig. 219 shows the stator lamina- 

 tions assembled, Fig. 220 shows the stator complete with its 

 windings, Fig. 221 shows the laminated core of the rotor 

 mounted on its shaft, and Fig. 222 shows the rotor com- 

 plete. The rotor shown in Fig. 222 is of the so-called squirrel- 

 cage type, and its windings consist of heavy copper rods placed 

 in nearly closed slots and connected at both ends to massive 



* The single-phase induction motor is described later. 



f Or like the windings of a direct-current armature with connections like the 

 alternating-current connections of a synchronous converter armature. 



2 5 I 



Fig. 218. 





