30 PROBLEMS IN ALTERNATING CURRENT MACHINERY 



reactance voltage at this load? Assume 7 leakage lines as 

 in (b). 



35. (a) In problem 28 what is the armature reaction in ampere 

 turns per pair of poles when the alternator is delivering 200 kw. 

 at 0.8 power factor, and its rated voltage? 



(b) What is the leakage reactance voltage at this load? The 

 armature inductors are 23 in. long. Assume that the leakage 

 flux is 8 lines per ampere per inch of inductor. 



(c) If the armature winding had been equally distributed in 

 the four central slots, i.e., with 4 inductors per slot, what would 

 have been the leakage reactance voltage at this load? Assume 

 8 leakage lines as in (b). 



36. (a) In problem 29 what is the armature reaction in ampere 

 turns per pair of poles when the alternator is delivering full-load 

 kilovolt-amperes? 



(b) What is the leakage reactance voltage per phase at this 

 load? Assume that the leakage flux is 96 lines per ampere per 

 inductor. 



(c) If the armature winding had been concentrated, i.e., with 

 one slot per pole per phase, holding 22 inductors, what would 

 have been the leakage reactance voltage? Assume the same 

 leakage flux per inductor as in (b) . 



37. (a) In problem 33 what is the armature reaction in ampere 

 turns per pole when the alternator is delivering 7650 kw. at 0.9 

 power factor and its rated voltage? 



(b) What is the leakage reactance voltage per phase at this 

 load? The armature inductors are 48 in. long. Assume that 

 the leakage flux is 6.5 lines per ampere per inch of inductor. 



38. A three-phase, Y-connected alternating-current generator 

 which is rated to deliver 760 kv.-a. at 2200 volts has an armature 

 with 6 slots per pole. There are 3 inductors in series per slot. 



What are the cross-magnetizing and demagnetizing ampere 

 turns per pole due to armature reaction when the alternator 

 delivers its full-load current (a) if the power factor is such that 

 the current in any phase reaches its maximum value 60 degrees 

 after the inductors of that phase pass the center of the pole? 

 (b) if the power factor is such that the current in any phase 

 reaches its maximum value of 30 degrees before the inductors of 

 that phase pass the center of the pole? 



39. A three-phase, 1500-kv.-a., 5500-volt alternating-current 

 generator has a field structure with 72 poles and an armature 



