REGULATING POLE CONVERTERS

443

between adjacent collector rings, and the current heating thus
a minimum in this coil.

Due to the lag in space, by angle TO, of the. direct-current
m.m.f. behind the alternating current m.m.f., the reversal of the
direct current is reached in time before the reversal of the alter-
nating current in the armature coil; that is, the alternating
current lags behind the direct current by angle, 00 = TO, in the

1!

FIG. 213.—Alternating and direct current in a coil midway between
adjacent collector leads.

armature coil midway between adjacent collector leads, as
shown by Fig. 213, and in an armature coil displaced by angle, T,
from the middle position between adjacent collector leads the
alternating current thus lags behind the direct current by angle
(? + #o), where r is counted positive in the direction of armature
rotation (Fig. 214).

FIG. 214. — Alternating and direct current in a coil at the angle r from the

middle position.

The alternating current in armature coil, T, thus can be ex-
pressed by:

i = /V2 sin (6 - r - 00); (11)

hence, substituting (9):

2 70fc . f - ,> N

sin (0— T — 00),

. TT

n-sm-
n

(12)

and as the direct current in this armature coil is ^ and opposite

A I, f"

Is1 T

I

If