REGULATING POLE CONVERTERS

427

The direct-current armature reaction, #, however, appears in the
position of the brushes, or shifted against quadrature position
by angle r; that is, the direct-current armature reaction is not in
opposition to the alternating-current armature reaction, but
differs therefrom by angle r, and so can be resolved into two
components, a component in opposition to the alternating-cur-
rent armature reaction, $o, that is, in quadrature position with
the resultant magnetic flux:

$" = S cos r = 9r0,

that is, equal and opposite to the alternating-current armature
reaction, and thus neutralizing the same; and a component in
quadrature position with the alternating-current armature reac-
tion, #0, or in phase with the resultant magnetic flux, that is,
magnetizing or demagnetizing:

& = $ sin r = ^o tan r;

that is, in the variable-ratio converter the alternating-current
armature reaction at unity power-factor is neutralized by a
component of the direct-current armature reaction, but a result-
ant armature reaction, $', remains, in the direction of the resultant
magnetic field, that is, shifted by angle (90 — T.) against the
position of brushes. This armature reaction is magnetizing or
demagnetizing, depending on the direction of the shift of the
field, T.

It can be resolved into two components, one at right angles
with the brushes:

CF'i = #' cos r = #0 sin T,
and one, in line with the brushes:

= 9r sin2 r = #0 sin r tan T,

as shown diagrammatically in Figs. 202 and 203.
There exists thus a resultant armature reaction in the direc-
tion of the brushes, and thus harmful for commutation, just as
in the direct-current generator, except that this armature reac-
tion in the direction of the brushes is only %\ = ^ sin2 r, that is,
sin2 T of the value of that of a direct-current generator.
The value of ^'2 can also be derived directly, as the difference
between the direct-current armature reaction, #, and the com-