. The influence of varying reactance upon the short circuit phenomena in alternators. voltage wave, the other uo record the voltage producedat tiie terminals of a small D. 0. generator coupled to the shaftof the alternator under test. As the speed of the armature ofthe alternator decreased after short-circuit, the driving powerbeing removed, the voltage of the D. C. generator decreased inproportion, Hence, the D. C. voltage wave on tne oscillogramwas a slanting one, and was an indication oi the deceleration,which from a 6U cycle calibration wave, could be reduced to revol-utions per second per
. The influence of varying reactance upon the short circuit phenomena in alternators. voltage wave, the other uo record the voltage producedat tiie terminals of a small D. 0. generator coupled to the shaftof the alternator under test. As the speed of the armature ofthe alternator decreased after short-circuit, the driving powerbeing removed, the voltage of the D. C. generator decreased inproportion, Hence, the D. C. voltage wave on tne oscillogramwas a slanting one, and was an indication oi the deceleration,which from a 6U cycle calibration wave, could be reduced to revol-utions per second per second, which are tiie units of n requiredin tne deceleration equation on page . uscillograms No. I andilo. II. show the results of two deceleration tests. Althoughthe slope of the D. u. voltage wave is not perfectly definite, anaverage line nas Deen drawn as shown, and from the slope of this1 line, the value of n was determined. 0-5c /11 y ocjT am if f fr#TM WMV/»W/l*>W<W,im\H WMUmriVnttii mimmmemnmmtk Speed, f^.Pn Osc ilIoq ram No. of Col cu I at ina n n =. cycle v^/ave. 22 Havim: determined tae value of n for each test, and knowingpreviously the value ot J, the watts dissipated can Do caicuJatedand tiie value ol tne short-circuit torque derived from tiie equationWatts = ^ NJn. Each retardation test was pertormed by running the alternatorat normal load, speed and voltage. m talcing an oscillogram,the driving torce was tirst removed irom uhe alternator, then theoscillograph shutter was opened and the short-circuiting switchautomatically closed, all three operations occurmg in successionas rapidly as possible. 23 IV. DISCUSSION OF RESULTS. Short-Circuit Current rests. xhe results obtained fromcalculations ana tesus made on the rotating armature machine arecomomed on curve sheet No IV., page 14- A study of thesecurves will show that tne experimental values01 short-circuitcurrent correspond very closely to those values obtained byusing variable values of
Size: 3211px × 778px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, booksubjecttheses, bookyear1913
