f I

388

ELECTRICAL APPARATUS

As seen, for S == 1, or at synchronism, J4 = 0, that is, the
short-circuit current under the commutator brushes of the re-
pulsion motor disappears at synchronism, as was to be expected,
since the armature coils revolve synchronously in a rotating field.

215. The e.m.f. of rotation, that is, the e.m.f. generated in the
rotor by its rotation through the magnetic field, which e.m.f.,
with the current in the respective circuit, produces the torque
and so gives the power developed by the motor, is:

Main circuit:

o/*-/4). (25)

Brush short-circuit:

int _ /CCV/ fj 7 \ fOA\

Q 4 = J&£ (./!"" f 2/« (."VJ

Substituting (18), (23), (24) into (25) and (26), and rearrang-
ing, gives:

Main Circuit E.m.f. of Rotation:

(28)
(29)

Brush Short-circuit E.m.f. of Rotation:

— coX4);

or, neglecting smaller terms:

K

The Power produced by the main armature circuit is:

Pi = Lff'i, JJ1,
hence, substituting (22) and (27):

Pi-

L

Let:

Xj -X

•4);

rn = [ZK]
be the absolute value of the complex product, ZK, and:

(30)

(31)

(32)

III