SYNCHRONOUS INDUCTION GENERATOR 195
called asynchronous generator and asynchronous motor, but
these names are wrong, since the induction machine is not
independent of the frequency, but depends upon it just as much
as a synchronous machine—the difference being, that the
synchronous machine runs exactly in synchronism, while the
induction machine approaches synchronism. The real asyn-
chronous machine is the commutating machine.
114. Since the slip of frequency with increasing load on the
induction generator with short-circuited secondary is due to
the increase of secondary frequency required to produce the
secondary e.m.f. and therewith the secondary currents, it follows:
if these secondary currents are produced by impressing an e.m.f.
of constant frequency, /i, upon the secondary circuit, the primary
frequency, /, does not change with the load, but remains con-
stant and equal to / = /o — /i- The machine then is a syn-
chronous-induction machine—that is, a machine in which the
speed and frequency are rigid with regard to each other, just as
in the synchronous machine, except that in the synchronous-
induction machine, speed and frequency have a constant dif-
ference, while in the synchronous machine this difference is zero,
that is, the speed equals the frequency.
By thus connecting the secondary of the induction machine
with a source of constant low-frequency, /i, as a synchronous
machine, or a commutating machine with low-frequency field
excitation, the primary of the induction machine at constant
speed, /o, generates electric power at constant frequency, /,
independent of the load. If the secondary fi = 0, that is, a
continuous current is supplied to the secondary circuit, the
primary frequency is the frequency of rotation and the machine
an ordinary synchronous machine. The synchronous machine so
appears as a special case of the synchronous-induction machine
and corresponds to fi = 0.
In the synchronous-induction generator, or induction machine
with an e.m.f. of constant low frequency, /i, impressed upon the
secondary circuit, by a synchronous machine, etc,, with increas-
ing load, the primary and so the secondary currents change, and
the synchronous machine so receives more power as synchronous
motor, if the rotating field produced in the secondary circuit
revolves in the same direction as the mechanical rotation—
that is, if the machine is driven above synchronism of the
e.m.f. impressed upon the secondary circuit—or the synchronous