Journal of electricity, power, and gas . 3/2. cos e —1/2. sin e Wi yV2. cos e + 1/2. sin e Dividing both numerator and denominator by 1 e, January 3, 1914.] JOURNAL OF ELECTRICITY, POWER AND GAS 15 Wi \/3 — tan eV3 + tan e (4) From Fig. 3 it is plain that the value (4) passesfrom + 1 to — 1 as the power factor varies. There-fore if values of (4) be assigned between these limits,corresponding values of e may be determined. Plac-ing (4) equal to x and solving for tan e, tane = V3. (1—x)/(l+x) Whence, the potential connection of this element should bereversed. The curves of Figs. 3 and 4 re
Journal of electricity, power, and gas . 3/2. cos e —1/2. sin e Wi yV2. cos e + 1/2. sin e Dividing both numerator and denominator by 1 e, January 3, 1914.] JOURNAL OF ELECTRICITY, POWER AND GAS 15 Wi \/3 — tan eV3 + tan e (4) From Fig. 3 it is plain that the value (4) passesfrom + 1 to — 1 as the power factor varies. There-fore if values of (4) be assigned between these limits,corresponding values of e may be determined. Plac-ing (4) equal to x and solving for tan e, tane = V3. (1—x)/(l+x) Whence, the potential connection of this element should bereversed. The curves of Figs. 3 and 4 readily afford a testof the balance of a three phase load. Let W> and W*abe the readings of the single phase meters— (or num-ber of revolutions of the watthour disks in a giveninterval)—and let W*> be the larger. If the circuitis balanced the value of WV(Wi + Wi) (this test failsat 50 per cent P. F. as W= becomes 0) should equalW=/(Wi + W=) where Wi and W= arc the valuesfound from Fig. 3 for the apparent power factor as. ;e = . -, which gives values —x + x2 of the power factor directly, and wherein the assumedvalues of x may readily be substituted. The curve ofFig. 4 was derived in this manner. It gives the powerfactor corresponding to any value of W=/Wi, whichmay be easily obtained by the slide rule from anygiven set of readings. The value of e may be read offat the same from the Phase Angle curve should italso be desired. When two single phase wattmeters are wired upon a circuit of unknown or varying power factor, thesign of the reading of W= may be in doubt. For exam-ple, an induction motor driven machine: In this case,if there is any way of loading the machine while thebehavior of W« may be observed, the right connec-tion may readily be seen. When load is thrown on themotor the power factor will rise, and hence if the read-ing of W= increases with the load, the power factoris known to be above 50 per cent. (See Fig. 3.) Thesame reasoning applies to po
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