86 ELECTRICAL APPARATUS

and peculiar speed characteristics result herefrom in such a
motor. At a certain slip, s, the condenser current just balances
all the reactive lagging currents of the induction motor, resonance
may thus be said to exist, and a very large current flows into the
motor, and correspondingly large power is produced. Above this
" resonance speed," however, the current and thus the power
rapidly fall off, and so also below the resonance speed.

It must be realized, however, that the frequency of the sec-
ondary is the frequency of slip, and is very low at speed, thus a
very great condenser capacity is required, far greater than would
be sufficient for compensation by shunting the condenser across
the primary terminals. In view of the low frequency and low
voltage of the secondary circuit, the electrostatic condenser
generally is at a disadvantage for this use, but the electrolytic
condenser, that is, the polarization cell, appears better adapted.

56. Let then, in an induction motor, of impressed voltage, eQ:

YQ = g — jb = exciting admittance;

ZQ = r0 + jxo — primary self-inductive impe-

dance;
Zi = TI + jxi = secondary self-inductive im-

pedance at full frequency;

and let the secondary circuit be closed through a condenser of
capacity reactance, at full frequency:

where r2, representing the energy loss in the condenser, usually is
very small and can be neglected in the electrostatic condenser,
so that:

£2 = - JX2-

The inductive reactance, xi, is proportional to the frequency,
that is, the slip, s, and the capacity reactance, #2, inverse propor-
tional thereto, and the total impedance of the secondary circuit,
at slip, s, thus is:

(1)
thus the secondary current :

es

= e (01 - ja2), (2)