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SINGLE-ENERGY TRANSIENTS. 51

symmetrical, and the double-frequency pulsation of the field cur-
rent shows during the first few cycles the alternate high and low
peaks resulting from the full-frequency transient pulsation of
the rotating magnetic field of armature reaction. The irregular
initial decrease of the armature current and the sudden change
of its wave shape are due to the transient of the current trans-
former, through which the armature current was recorded.

Fig. 25 shows a single-phase short circuit of a quarter-phase
alternator; the upper wave is the voltage of the phase which is
not short-circuited, and shows the increase and distortion resulting
from the double-frequency pulsation of the armature reaction.

While the synchronous reactance XG can be predetermined with
fair accuracy, the self-inductive o?i is not such a definite quantity,
It includes a transient component* The armature magnetic cir-
cuit is in mutual inductive relation with the field-exciting circuit.
At constant alternating current in the armature, the resultant
of the armature m.m.fs. and e.mJf's. is constant with regard to
the field, and the mutual inductance thus does not come into
play. During a transient, however, the armature conditions
change, and the self-inductance of the exciting circuit is partly
transformed into the armature circuit by the ratio of field turns
to armature turns, giving rise to a transient effective component
of armature self-induction, which depends on the relative rate of
•change of the armature and the field, and thereby is a maximum
in the beginning, and gradually decreases to ssero in stationary
conditions. This tends to lower the maximum values of the field
transients and to increase the duration of the armature tran-
sients. This effect is materially affected by the amount of resist-
ance and reactance in the exciting circuit outside of the field
winding.

There also exists a mutual inductance between the armature
•circuits of the three-phase machine, which results in an energy
transfer between the phases, during the armature transient*

The instantaneous power of the momentary short-circuit
current, and with it the forces acting on driving shaft and prime
mover, are proportional to the short-circuit current, being short-
circuit current times magnetic field flux. The forces exerted be-
tween the armature conductors — which tend to tear and strip
the end windings, etc. — are proportional to the square of the
short-circuit current.



	SINGLE-ENERGY TRANSIENTS. 51 symmetrical, and the double-frequency pulsation of the field cur- rent shows during the first few cycles the alternate high and low peaks resulting from the full-frequency transient pulsation of the rotating magnetic field of armature reaction. The irregular initial decrease of the armature current and the sudden change of its wave shape are due to the transient of the current trans- former, through which the armature current was recorded. Fig. 25 shows a single-phase short circuit of a quarter-phase alternator; the upper wave is the voltage of the phase which is not short-circuited, and shows the increase and distortion resulting from the double-frequency pulsation of the armature reaction. While the synchronous reactance XG can be predetermined with fair accuracy, the self-inductive o?i is not such a definite quantity, It includes a transient component* The armature magnetic cir- cuit is in mutual inductive relation with the field-exciting circuit. At constant alternating current in the armature, the resultant of the armature m.m.fs. and e.mJf's. is constant with regard to the field, and the mutual inductance thus does not come into play. During a transient, however, the armature conditions change, and the self-inductance of the exciting circuit is partly transformed into the armature circuit by the ratio of field turns to armature turns, giving rise to a transient effective component of armature self-induction, which depends on the relative rate of •change of the armature and the field, and thereby is a maximum in the beginning, and gradually decreases to ssero in stationary conditions. This tends to lower the maximum values of the field transients and to increase the duration of the armature tran- sients. This effect is materially affected by the amount of resist- ance and reactance in the exciting circuit outside of the field winding. There also exists a mutual inductance between the armature •circuits of the three-phase machine, which results in an energy transfer between the phases, during the armature transient* The instantaneous power of the momentary short-circuit current, and with it the forces acting on driving shaft and prime mover, are proportional to the short-circuit current, being short- circuit current times magnetic field flux. The forces exerted be- tween the armature conductors — which tend to tear and strip the end windings, etc. — are proportional to the square of the short-circuit current.