398 ELECTRICAL APPARATUS

1. Armature and field connected in. series with each other.
That is :

#! -f coE» = $ = e,, (67)

where :

Co = reduction factor of field winding to armature; that is,

f „ . field turns
ratio of effective armature turns'

It follows herefrom:

/o = co/i. (68)

2. The e.m.f. impressed upon the compensating winding is
given, and is in phase with the e.rn.f., €1, which is impressed upon
field plus armature :

lh = e*. (69)

That is, j^2 is supplied by the same transformer or compensator
as ei, in series or in shunt therewith.

3. No rotor-exciting circuit is used:

/» = 0, (70)

and therefore:

4. No rotor-exciting brushes; or brushes in quadrature posi-
tion with the main-armature brushes, eire used, and so:

I* = 0, (71)

that is, the armature carries only one set of brushes, which give
the short-circuit current, /4.

• Since the compensating circuit, 62, is an independent circuit,
it can be assumed as of the same number of effective turns as
the armature, that is, «2 is the e.m.f . impressed upon the com-
pensating circuit, reduced to the armature circuit. (The actual
e.ni.f. impressed upon the compensating circuit thus would be:

. • /* • compensating turns \

Co62, where Ca = ratio effective ~~~~ -- 7 -- -, ....... -

9 armature turns J

220. Substituting (68) into (1), (2), (3), and (5), and (1) and
(2) into (67), gives the three motor equations:

ei = 2x/i + Z' (h - h) - JS2 (co/! ™ /

^ = Z*h + Z' (J2 - /i), (73)
0 = W4 +Z(J<- co/0 - j&Z' (/! - /2) . (74)