National Republican., 1885-08-04
ELECTRICITY.

In our last paper we described, some.
what at length, the magnetic machine
and its mode Of operation, defining also
the Amperian theory and its bearing
upon this class of electrical generators.
Having, then, n correct knowledge Of
these matters, little difficulty need be
apprehended in understanding the dy
namo and its principle of action; for
the two classes of machines are entirely
analogous, particularly in respect to the
generation Of electrical currents by the |
carrying of conduclors at right angles TO |
the lines of magnetic force in magnetic |
field. The only essential difference be.
tween these two classes Of electrical gem
orators lies in the method of producing |
the magnetic field, and in this simple |
difference is found the solution of the
greatest problem in the art of generating
electricity economically.
In the magnetic machine, as will be
remembered, the field magnets, or the
magnets in whose proximity the arma
ture revolves, ara steel or permanent
magnets, presenting opposing poles to.
ward each other, thereby surrounding
the armature with strong magnetic
field.
In the dynamo these field magnets are
electro magnets formed by winding a
core or cores Of the purest soft iron with
insulated wire.
Let US suppose, for our purpose, there
is only one field magnet; let it be Of
horseshoe shape, of iron identically in
shape and construction with that de-
scribed in our last paper as constituting
the field for magnetic machine. Start
ing then with an insulated wire from
binding post located at IL point on our
left, let us wind this wire in layers about
the left leg Of this horseshoe of iron un.
Ill n sufficient number of turns have been
placed upon it to entirely magnetic
this leg, when current of electricity is
set up in the wire. Now carry this wire
from the last layer to the upper commu-
tator or conducting brush of the arma-
ture, which armature, as iR the magnetic
machine, is journaled between the two
legs of this field magnet. Now start
with similar insulated wire from the
lower commutator brush, and wind the
right leg in n reverse direction Herewith
until the same amount of wire as was
placed upon the first leg has been used,
and pass thence to binding post on the
right. Now connect this binding post
with wire and an electric light, motor,
or other translatiDg device, and finally
with the frst.named binding post, and
our machine is ready for action.
On rotating the armature, which, for
simplicity sake, we will assume to be Of
the Siemen's II type, before described,
the residual magnetism in the core
thereoftonds to polarze the field magnet,
one end north and the other south. This
polarization sets up light magnetic
field, having, as in the magnetic machine,
magnetic lines of force through which
the armaturc travels. Now, this action
of the armalure creates current of elec
triciiy through it's coils which further
polarizes it, causing it to still further
polarize the field magnet, the poles o
which in turn react and further polariat
the armature.
This action and reaction between th,
urmature and the poles of the ficl,
magnet continues until both are thor
oughly saturated magnelically, and whel
this occurs the machine ia working mt it
full capacity.
1t is to be understood, OF course, tha
this action takes place only on closure q
the external or working circuit, so tina
the electricity can pass throughout th
entire circuit and produce the effect
enumerated.
Let us trace now the course of this Gil
cult under the supposition that the ms
chine is working at full capacity. Star
ing from the left hand binding post, rs
convenient starting point, it goes theme
by the insulated wire from left to rigf
around the left end of the field magne
tendingto create a south polarity therein
aud on leaving the field magnet coil
poes TO upper commutator brush an
thence through the convoluions of VIII
on the armature, tending to produce
north polarity in the upper half an
south polarity in the lower half there'
during the first half revolution. Fro
the armature it passes out through Il
lower commutator brush and thence toll
right hand end Of the field magnet arour
it from right to left, tending to produt
north polarity therein. Finally 1t go
to the right hand binding post and them
to the light, motor, or work to be doI
under electric influence, and finally
the starting point.
At each half revolution Of the arm
ture the commutator brushes communal
or straighten the current, so that it {
ways passes in the same direction, u,
ahe field magnet poles are always polt
tzed in the same way.
This is the simplest form of dynGr
and is known as the series wound N
chine, being very effective machine
circuits where ~ constant electro'moti
force is desired, or in other words, whe
there is but littlN change in the work
be done, and wAere high tension cl
rents are needed, as in arc light circui
For circuits where great variation tai
place, as in incaudescent systems OF lig
ing, where consumers are constan
turning out and putting in light s,there
varying the. external circuit, what
known as u shunt wound machine
used. In this machine the exterior
working current goes directly from
commutator brushes of the armature
rhe work, and returns, while the II
magnets are engerized by derived
shunt crcuit, taken also from the arm
ture at the eommutators.
Regulating devices are placed in
shunt or field circuit for varying the
pacity of the machine, in accordal
with the demands indicated by the 81
of n light at the machine.
The dynamo is vastly more economi
in its generativc capacity than the M
neto, and for this reason it is possible
economically prodace light and trans'
rOwer by electricity. This economy
,,eoeraton ia due to two or three thin
CHIEF among which may be named W
yye will term the difficulty of overcom
the magnetic inertia Of the permain
moppeis in the magnetic, and agalr
the fact Tint it il not possible to etfet
ally magnetic piece of steel so as
< A,,nnriuu purIpnIg