Theory and calculation of alternating current phenomena . = constant. If the power of a synchronous motor remains constant, wehave (Fig. 154) I X OEi^ = constant, or, since OE^ = Ir, I = ^^^ and OE X OE^^ = OE X EE, = constant,r Hence we get the diagram for any value of the current, I, at p constant power, Pi, by making OE^ = Ir, E^Eo^ = -j erecting in £0^ a perpendicular, which gives two points of intersectionwith circle, eo, Eo, one leading, the other lagging. Hence, at agiven impressed , Eo, the same power. Pi, can be trans-mitted by the same current, /, with two different generatede.
Theory and calculation of alternating current phenomena . = constant. If the power of a synchronous motor remains constant, wehave (Fig. 154) I X OEi^ = constant, or, since OE^ = Ir, I = ^^^ and OE X OE^^ = OE X EE, = constant,r Hence we get the diagram for any value of the current, I, at p constant power, Pi, by making OE^ = Ir, E^Eo^ = -j erecting in £0^ a perpendicular, which gives two points of intersectionwith circle, eo, Eo, one leading, the other lagging. Hence, at agiven impressed , Eo, the same power. Pi, can be trans-mitted by the same current, /, with two different , El, of the motor; one, OEi = ££0 small, corresponding 312 ALTERNATING-CURRENT PHENOMENA to a lagging current; and the other, OEi = EEq large, corre-sponding to a leading current. The former is shown in dottedlines, the latter in full lines, in the diagram, Fig. 154. Hence a synchronovis motor can work with a given output, atthe same current with two different counter , Ei. In oneof the cases the current is leading, in the other Fig. 154. In Figs. 155 to 158 are shown diagrams, giving the points £0 = impressed , assumed as constant = 1000 volts,E = consumed by impedance,E^ = consumed by resistance (not numbered).The counter of the motor, Ei, is OEi, equal and parallel-££0, but not shown in the diagrams, to avoid complication. The four diagrams correspond to the values of power, or motoroutput. P = 1,000,P = 1,000P = 6,000P = 9,000P = 12,000 6,000, 9,000, 12,000 watts, and give:46 < £1 < 2,200, 1 < / < 49 340 < El < 1,920,540 < El < 1,750,920 < El < 1,320, 7 < / < < / < < / < 30 Fig. 155. Fig. 156. Fig. 157. Fig. 158. As seen, the permissible value of counter , Ei, and ofcurrent, /, becomes narrower with increasing output. SYNCHRONOUS MOTOR 313 Eo=lOOOP = 100046<Ei<22001<I<49
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