. Electrical world. e-phase current, the losses are very great, as soonas the alternating-current load is 25 per cent, of the maximum pos-sible direct-current load; and the greater the single-phase load be-comes the greater become the losses. A double-current generator,giving three-phase and direct-currents, is economical as long as theapparent three-phase power is not beyond 67 per cent, of the max-imum possible direct-current power; that is, for instance, as longas an armature which can give 100 kw direct current has not tofurnish more than 67 kw, three-phase currents at a power factorequal
. Electrical world. e-phase current, the losses are very great, as soonas the alternating-current load is 25 per cent, of the maximum pos-sible direct-current load; and the greater the single-phase load be-comes the greater become the losses. A double-current generator,giving three-phase and direct-currents, is economical as long as theapparent three-phase power is not beyond 67 per cent, of the max-imum possible direct-current power; that is, for instance, as longas an armature which can give 100 kw direct current has not tofurnish more than 67 kw, three-phase currents at a power factorequal to unity. The more phases are used the smaller become thecopper losses; but there is no use to increase the number of phasesbeyond six. If the double-current generator is operated on an in-dtictive load, tha copper losses become smaller than in the formercase.—Elek. Zeit., January 14. Single-Phase Motor.—An illustrated description of the Schiiler-Ferranti single-phase motor, which is a combination of an ordinary. the starting torque to be good, but to decrease rapidly. On the otherhand, when the same motor was run as a single-phase inductionmotor with a three-legged resistance in its rotor circuit, the torqueis zero at start, but increases gradually to a maximum. This be-havior is exactly opposite to that of the repulsion motor. Schiilercombined, therefore, these features of both types of machines in onemotor and the outcome is the arrangement shown in Fig. I. Atany speed the motor torque is approximately equal to the sum of thetorques due to the repulsion motor and to the induction single-phasemotor, respectively. This feature is shown in the curve of Fig. starting the three-legged resistance is inserted in full in the — — — — 5 . ^ \ fe S ^ y ^; S£SUe g 1^ - _ Current -^ =v- __ __ fiormal Tiorq ue —\ _ — .— No7m Ll C,urrf nl _ FIG. I.—DI.\GRAM OF CONNECTIONS OF SINGLE-PHASE MOTOR. single-phase induction motor and a repulsion motor. In some tests inwh
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectelectri, bookyear1883
