360 



INDEX 



Brush, width, usual limits, 178 

 Brushes, current density at contact 

 surface of, 178, 180 



friction losses at, 182, 227, 318 



I Z R losses at, 181 



Calorie, definition of, 47 

 CARTER, F. W., referred to, 116 

 Chorded armature windings, 85, 160 

 Circular lifting magnet, design of, 64 

 mils, definition 35, conversion 

 - factor, 36 



per ampere, conversion factor, 41 

 CLAYTON, A. E., referred to, 309 

 Clutch, magnetic, 50 

 Coefficient (see Cooling, Friction, 



Leakage, coefficient). 

 Commutating poles (see Interpoles). 

 Commutation, effect of brush re- 

 sistance on, 147, 175 

 of end flux on, 151 

 of field distortion on, 169 

 of slot leakage on, 149 

 ideal, or "straight line," 148 

 mechanical details affecting, 178 

 selective, 88 

 sparking limits, 175 

 theory of, 142 

 time of, 140, 162 

 Commutator, 180, 184 

 diameter of, 181 

 mica, thickness of, 177, 184 

 peripheral velocity of, 184 

 segments, number of, 90, 93, 223 

 thickness of, 181, 184 

 volts between, 94 

 temperature rise of, 181 

 Compensating windings (see Pole- 

 face windings). 



Concentrated windings (see Arma- 

 ture windings). 



Conductors (see Armature conduc- 

 tors). 



Conical pole faces, magnets with, 31 

 Cooling coefficient (magnet coils), 45 



(dynamo field coils), 194 

 of armatures, etc. (see Tempera- 

 ture rise). 



Copper wire, properties of, 33 

 resistance of, 36 

 tables, 34, 35, 38 

 weight of, 36, 47 

 Core (see Armature core). 

 Cost, important factor in design, 6 



of electromagnets, 49, 69 

 Critical speed of rotor, 327 

 Cultural subjects, value of study 



of, 8 

 Current density at brush contact 



surface, 178, 180 

 in armature conductors, 96, 259, 



328 



in coils of horseshoe magnet, 56 

 usual, in magnet windings, 41 

 in A.C. field winding, 300 

 in D.C. field winding, 192 



D 



Damping grids (see Pole-face wind- 

 ings). 



"Dead" coils in armature wind- 

 ings, 90 



Density (see Flux, Current, density). 



Distributed armature windings (see 



Armature), 

 field windings, 270, 335 



Distribution factor, 243 



Diverter, 193, 233, for interpoles, 

 168 



Dynamo, design sheets for 75 kw., 

 201 



A-connection, 244 



E 



Eddy-current losses (see Losses). 

 Efficiency of dynamo, 195, 197, 233 



of alternator, 317, 357 

 Electromagnets, circular type, 64 

 cost of, 49, 69 

 design of, 48, 53 

 short stroke plunger type, 64 

 E.m.f. (see also Voltage). 



developed in alternator armatures, 



242, 261, 291 



in dynamo armatures, 72, 138 

 by cutting of end flux (commu- 

 tation), 159 



