230 



ALTERNATING CURRENTS 



nected winding, as shown in Fig. 220. This is virtually a 

 continuous winding tapped at four equi-distant points. Two of 

 the diametrically opposite taps are connected to phase A and 

 the other two are connected to phase B. 



FIG. 220. Two-pole, mesh- 

 connected, gramme-ring winding 

 for a 2-phase circuit. 



FIG. 221. Four-pole, mesh-con- 

 nected, gramme-ring winding for a 

 2-phase circuit. 



Figure 221 shows a four-pole, mesh-connected winding. This 

 is similar to that of Fig. 220, but is tapped at eight equi-distant 

 points. Two diametrically opposite taps are connected to one 

 line of phase A and the two taps at right angles to these are 

 connected to the other line of phase A. Another similar set of 

 taps, displaced 45 from the A-taps, connect in like manner to 

 phase B. In such a winding, the rotating field completes one 

 revolution during two complete cycles of the current ; therefore its 

 angular speed is one-half that of the field in the two-pole machine. 

 Figure 222 shows the manner of connecting a three-phase cir- 

 cuit to a gramme-ring mesh- or delta-connected winding. Each 



of three equi-distant taps is connected 

 to one of the three lines of the three- 

 phase supply. This winding pro- 

 duces a two-pole field whose speed 

 in revolutions per second is the same 

 as the frequency of the supply. 



' FIG. 222. -Delta-connected, li is to be noted thai in each f the 



2-poie, gramme-ring winding for foregoing windings, the angle between 



the various windings expressed in elec- 

 trical space-degrees, is the same as the time-angles between the 

 respective currents in the windings. (In a two-pole machine one 

 electrical space-degree equals one space-degree; in a four-pole 

 machine two electrical space-degrees equal one space-degree, etc.) 



