. Revised and enlarged ed. of the science of railways . mechanical consists of two elements, one of Avhich is con-nected to the supply cir-cuit and receives currentin its windings. The cur-rent in the winding ofthe other element is in-duced from the currentin the primary, similarto the induced currents^ in the secondarv coil of Induction Motor; secondary, or revolving element, showing copper a transformer. i he COllS bars in which current is induced i i _ ^1^„,^ ^1 ^w-. ^, by the current iu the primary. OU the SeCOUdary elomCnt are completely closed orshort-circuited and th
. Revised and enlarged ed. of the science of railways . mechanical consists of two elements, one of Avhich is con-nected to the supply cir-cuit and receives currentin its windings. The cur-rent in the winding ofthe other element is in-duced from the currentin the primary, similarto the induced currents^ in the secondarv coil of Induction Motor; secondary, or revolving element, showing copper a transformer. i he COllS bars in which current is induced i i _ ^1^„,^ ^1 ^w-. ^, by the current iu the primary. OU the SeCOUdary elomCnt are completely closed orshort-circuited and there is no electrical contactwith the supply circuit. One of the windings,usually the primary, is placed upon the outsideor stationary part of the motor and in one typethe secondary or armature requires no commu-tator or contact of any kind for making electricalconnection. In one method of regulation of thismotor, a resistance is placed in the circuit of thesecondary which may be varied with correspond-ing changes in the speed or power of the 444 RAILWAY EQUIPMENT. The resistance is usually placed outside of themotor and connected with it by suitable this case, connection is made to the windingsof the armature by brushes resting on rings con-nected to the winding. The mechanical sim-plicity of the induction motor in its absence of commutator andusually of all openor moving contactsis particularly de-sirable in railwaywork. The induc-tion motor has,however, met butlittle progress inthe practical rail-way field. The rea-son for this is foundin its electricalcharacteristics. Itrequires for its suc-cessful operationtwo-phase or three-phase currents. There aremethods of operating an induction motor bysingle-phase currents, but in general they addconsiderably to the quantity of apparatus, reducethe output of the motor, lower the efficiency andgreatly impair the performance at low currents of more than one-phase requiremore than two conductors, so there mu
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