294

ELECTRICAL APPARATUS

when in parallel with other direct-current generators. Assum-
ing, then, in the general case the mechanical power consumed by
the load to vary, within the narrow range of speed variation con-
sidered during the oscillation, at the pth power of the speed,
in the preceding equation instead of Po is to be substituted,

If anti-surging devices are used, and even without these in
machines in which eddy currents can be produced by the oscilla-
tion of slip, in solid field poles, etc., a torque is produced more
or less proportional to the deviation of speed from synchronism.
This power assumes the form, PI = c2s, where c is a function of
the conductivity of the eddy-current circuit and the intensity
of the magnetic field of the machine, c2 is the power which
would be required to drive the magnetic field of the motor
through the circuits of the anti-surging device at full frequency,
if the same relative proportions could be retained at full fre-
quency as at the frequency of slip, s. That is, Pi is the power
produced by the motor as induction machine at slip s. In-
stead of P, the power generated by the motor, in the preced-
ing equations the value, P + Pi, has to be substituted, then:

The equation (8) assumes the form:

^ , -r, T-, ,„ s dM

(P - Po) - (Pi +
or, substituting (7) and (4):

(17)

and, for small values of <5:

dd

_ ee<> sin (a —
4 irfzMo

b =

(18)

(19)
(20)

Of these two terms b represents the consumption, a the oscilla-
tion of energy by the pulsation of phase angle, /3. 6 and a thus