366 



ELECTRICAL MACHINERY 



shown in the curves of Fig. 238. . It is seen that the current, 

 as well as the torque, varies greatly with the position of 

 the brushes. 



110. Compensated Repulsion Motor. The power factor 

 of the repulsion motor described in the last paragraph is 

 rather low and this is, of course, objectionable. Several 

 schemes have been developed for increasing the power 

 factor; a motor in which this is attempted is called a com- 

 pensated repulsion motor. 



The general scheme is to have a winding so placed on 

 either the field or armature that the field inductance is 



Main Field 



FIG. 239. One Method of Compensating a Repulsion Motor 



practically neutralized. One of the simplest of these schemes 

 is shown in Fig. 239. This type of motor was developed 

 by Winter and Eichberg; it gives the same characteristics 

 as the ordinary repulsion motor with the exception that 

 the power factor is much higher. The short-circuited 

 brushes are placed in the plane of the magnetic field and 

 an extra set of brushes, at right angles to the first pair, 

 are connected to the secondary of a transformer, the primary 

 of which is placed in the power supply line, in series with the 

 motor field winding. The secondary has several taps so that 

 the power factor may be maintained high at various speeds. 



