Journal of the Association of Engineering Societies . ein a field of the same strength, no current could, therefore, be in-duced, and hence no torque would result. The conductors slip backin consequence by an amount just sufficient to develop the currentnecessary to carry the load, this slip being nearly proportional tothe load, and rarely greater, at least for ordinary service, than 4 or5 per cent. This revolving flux is, of course, not of uniform intensity allaround the air-gap, but shades off from point to point, forming a 68 ASSOCIATION OF ENGINEERING SOCIETIES. succession of alternate nor
Journal of the Association of Engineering Societies . ein a field of the same strength, no current could, therefore, be in-duced, and hence no torque would result. The conductors slip backin consequence by an amount just sufficient to develop the currentnecessary to carry the load, this slip being nearly proportional tothe load, and rarely greater, at least for ordinary service, than 4 or5 per cent. This revolving flux is, of course, not of uniform intensity allaround the air-gap, but shades off from point to point, forming a 68 ASSOCIATION OF ENGINEERING SOCIETIES. succession of alternate north and south poles whose number dependsupon the arrangement of the field coil windings. Any given fixedarea in the air-gap is, therefore, threaded by magnetic lines of forcepassing through it first in one direction, then in the other, just as ifthe flux at that point was a simple alternating one. A conductorplaced there will then have induced in it an alternating , which,by the usual law, lags 900, or a quarter period, behind the FIG. 5 The inducing flux, or field, is due to the resultant magnetizingactions of the currents in the field coils and in the armature wind-ings. In Fig. 5, O* is this resultant field, while OM is the resultantmagnetizing force of the field and armature currents, OM beingslightly ahead of 0$ in phase due to hysteresis. This flux, as out-lined above, induces in the field and in the armature, whichlag 900 behind it and which are represented by the vectors Oex andOe2, respectively. The armature induced , Oe2, produces thearmature current, Oi2, which lags somewhat in phase behind Oe2due to self-induction, or magnetic leakage. The primary current,Oi-L, is then found by the use of the parallelogram law of vectorcombination, since OM must be the resultant of Oix and Oi2. The primary impressed must be of such magnitude andphase position that it will overcome (1) the , Oe^ induced bythe revolving field, (2) the dro
Size: 2779px × 900px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1880, booksubjectenginee, bookyear1881
