508 ELEMENTS OF ELECTRICAL ENGINEERING. 



Note. In a singly reentrant duplex winding, lap or wave, both front and back 

 pitches must be odd. 



224. Draw a singly reentrant duplex wave winding for a 4-pole 

 drum armature having 32 inductors ; front pitch 9 and back 

 pitch 9. Show connections to commutator bars and indicate 

 positions of poles and brushes. Make the drawing same size and 

 style as Fig. 60, Appendix C. 



225. Given a 4-pole drum armature which is to be wound with 

 20 inductors, (a) Can it be wound with a lap winding ? (b) 

 Can it be wound with a wave winding ? (c) State what windings 

 are possible when the number of inductors is taken as 22 and 

 24 respectively, and give front and back pitches for each case. 



226. Given a 6-pole drum armature having 40 inductors ar- 

 ranged as a duplex wave winding. What are the front and back 

 pitches and what is the degree of reentrancy ? 



227. Given a 6-pole drum armature having 52 inductors. 

 State the possible varieties of winding, and give front, back and 

 commutator pitches, and degree of reentrancy in each case. 



228. Given a 6-pole drum armature having 50 inductors. 

 State the possible varieties of winding, and give front, back, and 

 commutator pitches, and degree of reentrancy in each case. 



229 A 4-pole drum armature is to have from 46 to 50 induc- 

 tors, the exact number being chosen so that they may be ar- 

 ranged as a singly reentrant duplex wave winding having one- 

 fourth as many commutator bars as inductors. What number of 

 inductors is necessary ? Make a drawing somewhat similar to 

 Fig. 62, Appendix C, showing the winding and showing the 

 positions of the poles and brushes. 



230. A drum armature is to have 500 inductors and it is to be 

 driven at a speed of 600 revolutions per minute. 



(i) The number of poles is 6 and the useful flux per pole is 



4.8 x io 6 lines. Find electromotive force generated: (a) when 

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

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

 240 volts ; (b) 360 volts. 



