SYNCHRONOUS GENERATOR* 33 



in. There are 14 inductors in series per slot which occupy a 

 space 0.75 in. by 2.75 in. The thickness of the insulation 

 between the inductors and the armature core is the same at the 

 sides and at the bottom of the slot. The mean length of one 

 turn is 93 in. Each coil consists of 14 turns. 



(a) Calculate the leakage reactance per coil on the following 

 assumptions. Where the inductors are embedded in iron the 

 path of the leakage flux between the sides of the slot is parallel to 

 the bottom of the slot. For the portions of the coil that are 

 not embedded in the armature core the leakage flux links with 

 all of the turns in that coil and has a value of 0.8 line per ampere 

 per inch of turn. 



(b) If the leakage reactance is calculated on the assumption 

 that all of the leakage flux per coil links with all of the turns in 

 the coil, and that the length of the coil is but twice the length of 

 the inductor, i.e., twice the gross length of the armature core, 

 what value of leakage flux per ampere per inch of inductor will 

 give the same value of leakage reactance as calculated by the 

 preceding method? 



46. (a) Calculate the slot and coil end leakage reactance for 

 alternator A (see problem 40). Use the most exact method at 

 your command for the data given. 



(b) Calculate the slot and coil end leakage reactance for 

 alternator B (see problem 41). Use the most exact method at 

 your command for the data given. 



47. A special 60-cycle generator has a field structure with f> 

 poles and an armature with 72 slots. There are 9 inductor- in 

 series per slot. The coils in adjacent slots are connected in 

 series by pairs so that each of the <> independent armature wind- 

 ings thus formed has a spread of one-sixth and a pitch of 1.0. 

 When the 6 windings are arranged to form a 3-phase, Y-eon- 

 nected armature winding, the s\n< hronous reactance voltage 

 is 46 volts for an armature cum-m of 30 amperes. Assume 

 that the armature leakage flux is 72 lines per inductor per am- 

 pere, and that the approximate formula for armature reac- 



'/ 1 

 tion, 0.707 ^ holds exactly in every case. 



(a) What is the synchronous reactance voltage with an arma- 

 ture current nf :;i) ampem when the li armature windings are 

 connected in BOriefl to form a -i nude-phase, open-ciivuit armature 



winding? 



