tu ,

!l;

it ;i

t . M

.1;

442 ELECTRICAL APPARATUS

or, introducing for simplicity the abbreviation:

(1 _L_ t\ ('I _L ^>.\ n/->o _

A? -
it is:

T =

yj. -T ^z; u^a T« , ,

"cos^ .""' (8)

(9)

242. Let, in Fig. 212, A'OA represent the center line of the

magnetic field structure. __ ^

The resultant magnetic field flux, Oi>, then leads OA by angle

The resultant m.m.f. of the alternating power current, /i, is O/i,

B

Ii

FIG. 212.—Diagram of variable ratio converter.

at right angles to 0$, and the resultant m.m.f. of the alternating
reactive current, /2, is 0/2, in opposition to 0<£, while the total
alternating current, /, is 01, lagging by angle Bi behind OJi-

The m.m.f. of direct-current armature reaction is in the direc-
tion of the brushes, thus lagging by angle rb behind the position
OB, where BOA = 90°, and given by 0/0. __

The angle by which the direct-current m.m.f., O/o, lags in space
behind the total alternating m.m.f., O/, thus is, by Fig. 212:

TO = 01 - Ta - Tb. (10)

If the alternating m.m.f. in a converter coincides with the
direct-current m.m.f., the alternating current and the direct cur-
rent are in phase with each other in the armature coil midway

M f