RECTIFIERS: THE SYNCHRONOUS CONVERTER 345 



A six-phase, six-pole synchronous con vert or will have six slip- 

 ping and three taps from each slip-ring, making a total of 18 

 to the winding. 



A simple rule for obtaining the number of taps to the winding 

 is to remember that if the machine has n phases, there must be n 

 slip-ring taps for every 360 electrical spare-degrees, or for every 

 pair of poles. (This does not hold for single-phase.) For ex- 

 ample, in Fig. 31(5 there must be three taps for each pair of poles, 

 or six taps in all. Figure 327, page 357, shows how the taps are 



Fio. 316. Three-phase, 4-pole, synchronous converter. 



brought out from the armature to the -lip-rings in a 1 1-pole, 

 six-ph.-t-i- converter. 



It is to be noted that the slip-ring taps must .be brought out at 

 equidistant points along the winding, in order that the alter- 

 nating voltages may be balanced. Hence, the direct-current 

 winding that can be used for a synchronous converter are more 

 or tan n->t ricted. for the number of coils must be divisible by the 

 number nf >lip-ring taps. 



140. Single-phase Voltage Ratios in a Synchronous Converter. 

 In a synchronous converter, both the alternating and thedirect- 

 cunvnt electromotive forces are induced by the same system of 



