OF PAPER Part I treats of the calculation and application of the armature self-inductive reactance of synchronous machines. A short, reliable method is given in the form of curves, Figs. 20A, B, C, making the calculation from design sheet data a matter of a few minutes. Table I shows a comparison of calculated and test values (obtained from saturation and synchronous impedance curves) for 138 machines, ranging from high-speed turbine generators to the low-speed engine type.Three points were brought out during the investigation:(1) That in polyphase machines, the armature self-inductive reactance, just as the armature reaction, is a polyphase, not a single-phase phenomenon, and therefore the mutual induction of phases in a three-phase machine increases the effective selfinduction of each phase by approximately 50 per cent over the single phase value, while in two-phase machines, in which the mutual induction of phases is zero, the effective self-induction of the phase is the same for two-phase or single-phase operation.(2) That the variation of armature reactance during the cycle, due to salient-pole construction, is practically eliminated in Yconnected, three-phase machines for the reason that the variation, consisting almost entirely of a third harmonic, is cancelled in such machines. This leaves, in effect, a uniform reluctance for the leakage flux emanating from the tooth tips.(3) That in the familiar method of obtaining the armature self-induction from the saturation and synchronous impedance curves (i.e., by subtracting the armature reaction, that is, the de-

Synopsis.-During the pastfew years, stability characteristics of A series of curves and a formula for the minimum allowable systems using long lines have been discussed at considerable length, value of short-circuit ratio as a function of saturation and power but not so much attention has been given to the characteristics of factor are proposed for general purpose alternators which may be the load. This paper shows that power limits may be reached called upon to deliver power to any of the various classes of load. with very short lines and certain classes of load.These curves are derived from characteristic curves of typical The characteristics of several classes ofload, s.uch as motors of vari-machines. ous kinds with constant shaft output, variable impedance loads (syn-It is not intended that these curves shall be used for generators chronous converters for railways), constant impedance, and miscella-which supply power over long transmission lines, as the characterneous combinations, are discussed as they affect the stability of the gen-istics of these lines may require considerably higher values of shorterator. The criterions for the stability of an alternator as developed by circuit ratio, and the generator must be specially designed to meet this paper are "short-circuit ratio," saturation, power factor of the the individual requirements.

No abstract

No abstract

Synopsis,-Duringthe past few years, stability characteristics of systems using long lines have been discussed at considerable length f but not so much attention has been given to the characteristics of the load. This paper shows that power limits may be reached with very short lines and certain classes of load.The characteristics of several classes of load, such as motors of vari ous kinds with constant shaft output, variable impedance loads (syn chronous converters for railways), constant impedance, and miscella neous combinations, are discussed as they affect the stability of the gen erator. Thè criterions for the stability of an alternator as developed by this paper are "short-circuit ratio, 11 saturation, power factor of the load, and character of the load.A series of curves and a formula for the minimum allowable value of short-circuit ratio as a function of saturation and power factor are proposed for general purpose alternators which may be called upon to deliver power to any of the various classes of load. These curves are derived from characteristic curves of typical machines.It is not intended that these curves shall be used for generators which supply power over long transmission lines, as the characteristics of these lines may require considerably higher values of shortcircuit ratio, and the generator must be specially designed to meet the individual requirements.