CHAPTER XXIII
REVIEW
£53. In reviewing the numerous types of apparatus, methods
of construction and of operation, discussed in the preceding,
an alphabetical list of them is given in the following, comprising
name, .definition, principal characteristics, advantages and dis-
advantages, and the paragraph in which they are discussed.
Alexanderson High-frequency Inductor Alternator.—159.
Comprises an inductor disk of very many teeth, revolving at very
high speed between two radial armatures. Used for producing
very high frequencies, from 20,000 to 200,000 cycles per second.
Amortisseur.—Squirrel-cage winding in the pole faces of the
synchronous machine, proposed by Leblanc to oppose the hunt-
ing tendency, and extensively used.
Amplifier.—161. An apparatus to intensify telephone and
radio telephone currents. High-frequency inductor alternator
excited by the telephone current, usually by armature reaction
through capacity. The generated current is then rectified, be-
fore transmission in long-distance telephony, after transmission
ir> radio telephony.
Arc Machines.—138. Constant-current generators, usually
direct-current, with rectifying commutators. The last and most
extensively used arc machines were:
Brush Arc Machine.—141-144. A quarter-phase constant-
current alternator with rectifying commutators.
Thomson-Houston Arc Machine.—141-144. A three-phase
Y-connected constant-current alternator with rectifying commu-
tator.
The development of alternating-current series arc lighting by
constant-current transformers greatly reduced the importance
of the arc machine, and when in the magnetite lamp arc
lighting returned to direct current, the development of the
mercury-arc rectifier superseded the arc machine.
Asynchronous Motor.—Name used for all those types of
alternating-current (single-phase or polyphase) motors or motor
couples, which approach a definite synchronous speed at no-load,
and slip below this speed with increasing load.