Various motors have been constructed on this principle, but none have
attained any practical importance. Owing to the low temperature at which
it loses its paramagnetic properties nickel is the best metal for
paramagnetic motors.
In Edison's motor, between the pole pieces of an electro-magnet a
cylinder made up of a bundle of nickel tubes is mounted, so as to be
free to rotate. A screen is placed so as to close or obstruct the tubes
farthest from the poles. On passing hot air or products of combustion of
a fire or gas flame through the tubes, the unscreened ones are heated
most and lose their paramagnetism. The screened tubes are then attracted
and the armature rotates, bringing other tubes under the screen, which
is stationary. Then the attracted tubes are heated while the others
cool, and a continuous rotation is the result.
Fig. 279. EDISON'S PYROMAGNETIC MOTOR.
Pyromagnetic Generator.
A current generator producing electric energy directly from thermal
energy by pyromagnetism.
Edison's pyromagnetic generator has eight electro-magnets, lying on
eight radii of a circle, their poles facing inward and their yokes
vertical. Only two are shown in the cut. On a horizontal iron disc are
mounted eight vertical rolls of corrugated nickel representing
armatures. On each armature a coil of wire, insulated from the nickel by
asbestus is wound. The coils are all in series, and have eight
connections with a commutator as in a drum armature. There are two main
divisions to the commutator. Each connects with an insulated collecting
ring, and the commutator and collecting rings are mounted on a spindle
rotated by power. Below the circle of vertical coils is a horizontal
screen, mounted on the spindle and rotating with it.
A source of heat, or a coal stove is directly below the machine and its
hot products of combustion pass up through the coils, some of which are
screened by the rotating screen. The effect is that the coils are
subjecting to induction owing to the change in permeability of the
nickel cores, according as they are heated, or as they cool when the
screen is interposed. The two commutator segments are in constant
relation to the screen, and current is collected therefrom and by the
collecting rings is taken to the outside circuit.