PROBLEMS. 509 



(2) The number of poles is 8 and the useful flux per pole is 

 3.6 x io 6 . Find the electromotive force generated: (a) when 

 the inductors are arranged as a simplex lap winding ; (b) when 

 the inductors are arranged as a duplex lap winding. Ans. (a) 

 1 80 volts ; (b) 90 volts. 



231. In order to generate the desired electromotive force in a 

 6-pole drum armature it is decided to use about 670 inductors 

 and arrange them as a singly reentrant triplex wave winding. 



(a) What is the exact number of inductors required ; and (ft) 

 what are the front and back pitches ? 



232. A 4-pole simplex lap drum winding has '576 inductors. 

 The diameter of the bare wire is 0.08 1 inch, and the mean length 

 of one " armature turn " (consisting of two inductors and two end 

 connectors) is 1 6 inches. Find the resistance (cold) of the wind- 

 ing from positive to negative brushes. Ans. 0.0395 ohm. 



233. An 8-pole drum armature has a duplex, lap winding with 

 1,258 inductors. Find : (a) front, back, and commutator pitches ; 



(b) degree of reentrancy ; and (c) number of paths between the 

 brushes. Is the winding symmetrical ? Why ? 



234. A certain Siemens and Halske 1 4-pole 1,000 kilowatt 

 generator has a quintuple wave wound drum armature with 1,144 

 inductors. Find : (a) front, back, and commutator pitches ; and 

 (b] degree of reentrancy. 



235. An 8-pole duplex wave -wound drum armature is to be 

 driven at a speed of 100 revolutions per minute, and the useful 

 flux per pole is 8.3 x io 6 lines. How many inductors are needed 

 to generate 150 volts? Ans. 542 inductors. 



