. Electric railways, theoretically and practically treated . sthe current in the armature and field coils will reversesimultaneously. The ordinary type of direct current seriesmotor when operated upon an alternating current has a lowpower factor and low efficiency, due to the fact that addi-tional !^ of self-induction are set up in the wind-ings by the alternating magnetic flux. In addition to theseinductive £. J/./^.s, large hysteresis losses are present. 88 ELECTRIC RAILWAYS. The , of self-induction also exist in the alter-nating current single phase motor, but their effect in su
. Electric railways, theoretically and practically treated . sthe current in the armature and field coils will reversesimultaneously. The ordinary type of direct current seriesmotor when operated upon an alternating current has a lowpower factor and low efficiency, due to the fact that addi-tional !^ of self-induction are set up in the wind-ings by the alternating magnetic flux. In addition to theseinductive £. J/./^.s, large hysteresis losses are present. 88 ELECTRIC RAILWAYS. The , of self-induction also exist in the alter-nating current single phase motor, but their effect in suchmachines is diminished by proper design. The usualmethod of procedure is to eliminate the armature inductiveE. M. F. and to reduce the field inductive E. J\L F. to a min-imum. One method of neutralizing the armature induc-tive , consists in placing an additional winding atright angles electrically to the field coils. This additionalwinding, called the compensating coil, may be connected inreverse series with the field coils, Fig. 48, or short cir-. Fig. 49. SINGLE PHASE MOTOR WITH SHORT CIRCUITED COMPENSATINGWINDING. cuited upon itself as in Fig. 49. With either method theself-induction of the armature may be neutralized. The self-induction of the field windings may be dimin-ished in several ways, as will be discussed later. The proportion of armature turns to field turns is usuallyso adjusted that with large armature turns and few fieldturns the E. M. F. of the field coils is small compared withthe E. M. F. of the armature. The field E. M. F., being in- ALTERNATING SINGLE PHASE MOTORS. 89 ductive, is at right angles to the armature (). Upon their relative magnitude depends the powerfactor of the motor. The armature represents theenergy component, whereas the field E. M. F. represents thewattless component. Referring to Fig. 50, ABpower factor = ~irr Phenomena. — The alternating flux in an alternatingcurrent motor produces many phenomena, the more
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