Fig. 27. OPEN COIL RING ARMATURE.
47 STANDARD ELECTRICAL DICTIONARY.
Armature, Pivoted.
An armature for an electro-magnet mounted on a pivot, which is at right
angles to the yoke or parallel with the legs of the magnet, so as to be
free to rotate. When the magnet is excited the armature is drawn into
line or approximately so with its base or yoke. The system is used in
some telegraph apparatus.
Armature Pockets.
Spaces or recesses in armatures provided for the reception of the coils.
Armature, Polarized.
An armature made of steel or having a steel core to which permanent
magnetism has been imparted. Such are used in some forms of magneto
current generators, and in telegraphic instruments. (See Relay,
Polarized.)
Armature, Pole.
An armature having coils wound on separate poles projecting radially all
around the periphery of its central hub or disc, or projecting
internally from a ring-like frame, their ends facing the field magnet.
Synonym--Radial Armature.
Armature, Quantity.
An armature of a dynamo or motor wound for current of large quantity.
The term is now but little used.
Armature-Reactions.
When an armature is running in an active dynamo a series of
reactions is established, the more important of which are:
I. A tendency to cross-magnetize the armature.
II. A tendency to spark at the brushes.
III. A tendency for the armature current to demagnetize on account of
the lead which has to be given to the brushes.
IV. Variations in the neutral points as more or less current is taken
from the machine.
V. Heating of armature, both core and conductors, and of pole pieces,
which heating is due to Foucault currents.
Armature, Revolving, Page's.
An early form of motor. The field is produced by a permanent magnet.
Above its poles is a soft iron armature wound with a coil of insulated
wire. A two-part commutator with contact springs conveys the current to
the coil. The whole is so arranged that the polarity of the armature, as
induced by the coil, through which a current is passed, is reversed as
its ends sweep by the poles of the magnet. Then it is repelled from the
poles and swings through 180° to have its polarity reversed and to go
through the next 180°, and so on. Thus it rotates at a very high rate of
speed.
In the cut showing the elevation A, B, is the armature; f, g, the
springs or brushes; h, the commutator with its sections o, i. In the
section of the commutator W, W, designate the springs or brushes, A, the
vertical spindle carrying the armature and commutator, and S, S, the
commutator sections.
48 STANDARD ELECTRICAL DICTIONARY.
Fig. 28. PAGE'S REVOLVING ARMATURE.
Fig. 29. SECTION OF COMMUTATOR OF PAGE'S REVOLVING ARMATURE.
W, W, Brushes; A, Spindle; S, S, Armature Segments.
Armature, Ring.
An armature whose core is in the shape of a ring, as the Gramme Ring
Armature. (See Figs. 23 & 27.)
49 STANDARD ELECTRICAL DICTIONARY.
Armature, Rolling.
(a) An armature for a permanent horseshoe magnet consisting of a
straight cylinder of soft iron on which a heavy wheel is mounted. When
the legs of the magnet are inclined downward and the bar is laid across
them it rolls down to the poles, across their ends, and back up the
under side. It is merely a magnetic toy or illustrative experiment.
Synonym--Wheel Armature.
(b) Another form consists of little bars of iron with brass discs
attached to the ends. On placing two of these together and bringing the
poles of a magnet near them, as shown, they become magnetized with like
polarity by induction and repel each other, rolling away in opposite
directions.
Fig. 30. ROLLING OR WHEEL ARMATURE.
Fig. 31. ROLLING ARMATURES.
Armature, Shuttle.
The original Siemens' armature, now discarded. The core was long and
narrow, and its cross section was nearly of the section of an H. The
grooves were wound full of wire, so that the whole formed almost a
perfect cylinder, long and narrow comparatively. (See Winding Shuttle.)
Synonym--Siemens' Old Armature--Girder Armature--H Armature.
Fig. 32. SHUTTLE OR H ARMATURE.
Armature, Spherical.
An armature of a dynamo which is wound on a spherical core, so as to be
almost a sphere. It is employed in the Thomson-Houston dynamo, being
enclosed in a cavity nearly fitting it, formed by the pole pieces.
Armature, Stranded Conductor.
A substitute for bar-armatures in which stranded copper wire conductors
are substituted for the solid bar conductors, to avoid Foucault
currents. (See Armature, Bar.)
50 STANDARD ELECTRICAL DICTIONARY.
Armature, Unipolar.
An armature of a unipolar dynamo. (See Dynamo Unipolar.)
Armor of Cable.
The metal covering, often of heavy wire, surrounding a telegraph or
electric cable subjected to severe usage, as in submarine cables.
Synonym--Armature of Cable.
Arm, Rocker.
An arm extending from a rocker of a dynamo or motor, to which arm one of
the brushes is attached. (See Rocker.) Ordinarily there are two arms,
one for each brush.
Articulate Speech.
Speech involving the sounds of words. It is a definition which has
acquired importance in the Bell telephone litigations, one contention,
concerning the Bell telephone patent, holding that the patentee did not
intend his telephone to transmit articulations, but only sound and
music.
Astatic. adj.
Having no magnetic directive tendency due to the earth's magnetism.
Examples are given under Astatic Needle; Circuit, Astatic; and
Galvanometer Astatic.