430 ELEMENTS OF ELECTRICAL ENGINEERING. 



A triplex winding consists, in the simplest cases, of three 

 similar simplex windings with their commutators, sandwiched 

 together on one core and put in parallel by using sufficiently 

 thick brushes to insure contact with all three windings at each 

 brush. 



Any number of simplex wave windings with their commutators 

 may be sandwiched together as above described, giving a multi- 

 plex wave winding. 



Any winding not a simplex winding is in general called a 

 multiplex winding, although the above description of a multiplex 

 winding as built up of independent and complete simplex windings 

 sandwiched together, is not entirely general. 



The advantage of multiplex over simplex windings is that 

 sparking at the brushes is reduced by the use of multiplex 

 windings. In a simplex winding one winding element is short- 

 circuited when a brush touches two adjacent commutator bars as 

 explained in Art. 78, Chapter VI., and a brush must at certain 

 instants touch two adjacent commutator bars. In a duplex 

 winding no portion of the winding is short-circuited when a brush 

 touches two adjacent commutator bars ; short-circuit only occurs 

 when a brush touches three adjacent bars, and, although a brush 

 must at certain instants touch three adjacent bars in a duplex 

 winding, still the short-circuit includes a greater length of path 

 in the material of the brush than in case of a simplex winding, 

 and the resistance of the brush material is more effective in the 

 prevention of sparking. 



49. Number of paths in parallel. Number of inductors in 

 series. In the simplex lap winding there are / paths in parallel 

 between the positive and the negative brushes, where p is the 

 number of field poles. Therefore there are Zip inductors in 

 series in each path. 



In a simplex wave winding there are two paths in parallel be- 

 tween the positive and the negative brushes irrespective of the 

 number of poles and of the number of brush sets. Therefore 



