298 



THE DIRECT-CURRENT MOTOR 



PERIPHERAL velocity, 175 

 Pinion defined, 49 



number of teeth in, 50 

 Pole-tip, magnetisation under, 263 



effect of tapering, 275 



effect of cutting, 281 

 Power, equation for, 21 



RATING of motors : 



by the force factor, 169 

 by horse-power, 169 

 by tractive effort, 56 

 Reaction. See Armature 

 Resistance, train, defined, 244 

 Rheostat, starting, 40, 60, 184 

 Ring winding, 7 

 Roller bearings, use of, 215 



SELF-INDUCTION' in armature circuit, 



285 

 Series-parallel control, 192, 196, 



200, 221, 231, 247 

 Series-winding, 94, 234, 239 

 Shunt-winding, 60 

 Slipping of motors connected in 

 series, 120 



of belt, 159 



Spark, tendency to, equation giving, 



286 

 Sparkless commutation, conditions 



of, 279 



Speed curve of series-wound motor, 

 96 



of shunt-wound motor, 30 



Speed of motors in series, 113, 115, 



197, 203 



Speed regulation by compound 

 winding, 65 



- by reaction, 66 

 Speed, variation of : 



with induction factor, 62, 96 

 with load, 60, 118 

 with resistance, 61 

 with tension, 66, 118 



Steel magnets, 102, 111 

 Steering gear, electric, 93 



TEETH, number of, in gear wheel, 

 49 



tendency of, to cut, 58 

 Tension, induced, equation for, 13 

 Testing, Hopkinson's method of, 



84 

 -electrical method of, 87 



series-wound motors, 143 

 Thermodynamics, second law of, 26 

 Time factor defined, 151 

 Torque, equation for, 5 



losses, to find, 129, 145 

 Train resistance. See Friction 

 Turret, equation giving M for, 57, 



154 



VELOCITY, peripheral, 175 



ratio defined, 48 



values of, in railway motors, 50 



determination of best, 142, 209, 

 222, 237, 245 



WALKER railway generators, data of, 



180 



Watt-meter, 71 

 Weight, limit of, in railway motors, 



236 



Weights of dynamos, 175 

 Westinghouse motors, efficiency of, 

 140 



generator, force factor of, 170 

 Wheel, driving, to find the best 



diameter of, 142, 209, 222, 237, 

 . 245 

 Work, definition of, 25 



distinction between heat and, 



24 

 Working, rate of, equation for, 21 



maximum possible, 32 

 Worm gearing, use of, in lifts, 58 



fyoltisiroo-Je it Co. Prittteri, Neu '-street Square, Lu/itlun. 



