I

460

ELECTRICAL APPARATUS

Brush Arc Machine.—(See "Arc Machines.")
Compound Alternator.—138. Alternator with rectifying com-
mutator, connected in series to the armature, either con-
ductively, or inductively through transformer, and exciting a,
series field winding by the rectified current. The limitation of
the power, which can be rectified, and the need of readjusting the
brushes with a change of the inductivity of the load, has made such
compounding unsuitable for the modern high-power alterna-
tors.
Condenser Motor.—77. Single-phase induction motor with
condenser in tertiary circuit on stator, for producing starting
torque and high power-factor. The space angle between pri-
mary and tertiary stator circuit usually is 45° to 60°, and often a
three-phase motor is used, with single-phase supply on one phase,
and condenser on a second phase. With the small amount of
capacity, sufficient for power-factor compensation, usually the
starting torque is small, unless a starting resistance is used, but
the torque efficiency is high.
Concatenation.—III, 28. Chain connection, tandem connec-
tion, cascade connection. Is the connection of the secondary of
an induction machine with a second machine. The second
machine may be:
1. An Induction Machine.—The couple then is asynchronous.
Hereto belong:
The induction frequency converter or general alternating-current
transformer, XII, 103. It transforms between alternating-cur-
rent systems of different frequency, and has over the induction-
motor generator set the advantage of higher efficiency and lesser
capacity, but the disadvantage of not being standard.
The concatenated couple of induction motors, 9, 28, 111. It
permits multispeed operation. It has the disadvantage against
the multispeed motor, that two motors are required; but where
two or more motors are used, as in induction-motor railroading,
it has the advantage of greater simplicity.
The internally concatenated motor (Hunt motor}, 36. It is
more efficient than the concatenated couple or the multispeed
motor, but limited in design to certain speeds and speed ratios.
2. A Synchronous Machine.—The couple then is synchronous.
Hereto belong:
The synchronous frequency converter, XII, 103. It has a defi-
nite frequency ratio, while that of the induction frequency con-