Dynamo, Direct Current.
A dynamo giving a current of unvarying direction, as distinguished from
an alternator or alternating current dynamo.
Dynamo, Disc.
A dynamo with a disc armature, such as Pacinotti's disc, q. v. (See also
Disc, Armature.) The field magnets are disposed so that the disc rotates
close to their poles, and the poles face or are opposite to the side or
sides of the disc. The active leads of wire are those situated on the
face or faces of the disc.
Fig. 138. POLECHKO'S DISC DYNAMO.
Dynamo-electric Machine.
A machine driven by power, generally steam power, and converting the
mechanical energy expended on driving it into electrical energy of the
current form. The parts of the ordinary dynamo may be summarized as
follows: First, A circuit as complete as possible of iron. Such circuit
is composed partly of the cores of an electro-magnet or of several
electro-magnets, and partly of the cylindrical or ring-shaped core of an
armature which fits as closely as practicable between the magnet ends or
poles which are shaped so as to partly embrace it. Second, of coils of
insulated wire wound upon the field-magnet cores. When these coils are
excited the field-magnets develop polarity and the circuit just spoken
of becomes a magnetic circuit, interrupted only by the air gaps between
the poles and armatures. Thirdly, of coils of insulated wire upon the
armature core. These coils when rotated in the magnetic field cut
magnetic lines of force and develop electro-motive force.