SINGLE-PHASE COMMUTA TOR MOTORS 385

10. Rotor-excited series motor with conductive compensation:

e = Ei + c2#2 + c3#3; /2 = c2/i; 73 = c3/i; /o = 0.

11. Rotor-excited series motor with inductive compensation:

e = #1 + c3$3; #2 = 0; /o = 0; J3 = c3/!.

Numerous other combinations can be made and have been
proposed.

All of these motors have series characteristics, that is, a speed
increasing with decrease of load. _ __

(1) to (8) contain only one set of
brushes on the armature; (9) to (11)
two sets of brushes in quadrature.

Motors with shunt characteristic,
that is, a speed which does not vary

greatly with the load, and reaches such FlG 187

a definite limiting value at no-load

that the motor can be considered a constant-speed motor, can
also be derived from the above equations. For instance:
Compensated shunt motor (Fig. 187) :

#1 = 0; c2#2 = c8#8 = e; /0 - 0.
In general, a series characteristic results, if the field-exciting
circuit and the armature energy circuit are connected in series
with each other directly or inductively, or related to each other
so that the currents in the two circuits are more or less propor-
tional to each other. Shunt characteristic results, if the voltage
impressed upon the armature energy circuit, and the field excita-
tion, or rather the magnetic field flux, whether produced or in-
duced by the internal reactions of the motor, are constant, or,
more generally, proportional to each other.
Repulsion Motor
As illustration of the application of these general equations,
paragraph 212, may be considered the theory of the repylsion
motor (5), in Fig. 186.
214. Assuming in the following the armature of the repulsion
motor as short-circuited upon itself, and applying to the motor
the equations (1) to (6), the four conditions characteristic of the
repulsion motor are: