Til K TNDUCTION M<>rni{ 



241 



Therefore, in order to have maximum torque v mhies of 



cnrn-nt (iml flux, the rotor currents should be in ^pace-phase with 

 tkeflux. 



The torque 



T = T max cos a 



where T mnx is the torque when the current I and the flux <f> are 

 in space-phase and a is the space-angle between the current I 

 and the flux </>. 



104. The Squirrel-cage Motor. The squirrel-cage motor is the 

 simplest type of induction motor and is the most generally used. 

 The core of the rotor or armature, Fig. 229, like that of the direct- 



FIG. 229. Squirrel-rune rotor. 



current armat ure. ,is usually built up of -lotted steel punching*. 

 The winding consists of copper bars placed in .-lots. These 

 bars have their ends connected together by conduct ing rings 

 called r ////-//// r/x. The bars are usually bolted to the end-rings 

 and then welded or bra/ed. Formerly solder was used, but 



i.-rablr trouble was .-nrount rn-d by its melting and being 

 thrown out of the joint by centrifugal a.-tion. Another method 

 is to place the rotor in a mould and cast the ends of the bars in a 



ieral Fleet lie ( ... manufactures a 

 rotor in which an aluminum grid is cast integral with the end- 



The methods in which the end-ring* are cast in' 

 with the bars of the winding are tin m the operating 



IQ 



