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.