Dynamo, Iron Clad.
A dynamo in which the iron of the field magnet is of such shape as to
enclose the field magnet coils as well as the armature.
Dynamometer.
A device or apparatus for measuring force applied, or rate of
expenditure of energy by, or work done in a given time by a machine. A
common spring balance can be used as a force dynamometer, viz: to
determine how hard a man is pulling and the like. The steam engine
indicator represents an energy-dynamometer of the graphic type, the
instrument marking an area whence, with the aid of the fixed factors of
the engine, the work done may be determined. Prony's Brake, q. v., is a
type of the friction dynamometer, also of the energy type. In the latter
type during the experiment the whole power must be turned on or be
expended on the dynamometer.
Dynamo, Motor.
A motor dynamo is a machine for (a) converting a continuous current at
any voltage to a continuous current of different strength at a different
voltage or for (b) transforming a continuous current into an alternating
one, and vice versa.
For the first type see Transformer, Continuous Current; for the second
type see Transformer, Alternating Current.
Dynamo, Multipolar.
A dynamo having a number of field magnet poles, not merely a single
north and a single south pole. The field magnet is sometimes of a
generally circular shape with the poles arranged radially within it, the
armature revolving between the ends.
Dynamo, Non-polar.
A name given by Prof. George Forbes to a dynamo invented by him. In it a
cylinder of iron rotates within a perfectly self-contained iron-clad
field magnet. The current is taken off by brushes bearing near the
periphery, at two extremities of a diameter. A machine with a disc 18
inches in diameter was said to give 3,117 amperes, with 5.8 volts E. M.
F. running at 1,500 revolutions per second. The E. M. F. of such
machines varies with the square of the diameter of the disc or cylinder.
Dynamo, Open Coil.
A dynamo the windings of whose armatures may be grouped in coils, which
are not connected in series, but which have independent terminals. These
terminals are separate divisions of the commutator and so spaced that
the collecting brushes touch each pair belonging to the same coil
simultaneously. As the brushes come in contact with the sections forming
the terminals they take current from the coil in question. This coil is
next succeeded by another one, and so on according to the number of
coils employed.
Dynamo, Ring.
A dynamo the base of whose field magnets is a ring in general shape, or
perhaps an octagon, and with poles projecting inwardly therefrom.