National Republican., 1885-09-26
Orders BY Mail Prompt
ELECTRIC SCIENCE.

Paper No. q, by q. j. Eintner, Princi-
pal Examiner, United Siatos Patent
Onice-Transmission of Power-Eiec-
trio Motors.
II our readers have retained In their mem
ory the description given In paper No. 3 OF
n dynamo machine, they will understand
for all substantial purposes that of the mod
crn electric motor, inasmuch as the two
machines are almost identical In form, the
principal difference being that electric mo.
tors are generally more diminutive IN size,
Tut even this limitation OF degree IN the
machine is only dependent upon the work
expected tlcrcfrOm. On the suppOsitlon,
then, that the device Is understood, we will
pass TO It's mode Of operation.
An electric motor Is put In operation by
passing n current Of electricity through It's
Held magnets and amature, as follows:
Starting from the plus or positive binding
post OF the dynamo generator, the current
goes by conductor or wire to the entering
binding post OF the motor, thence through
the cOnvulutlOns Of wire about one field
magnet, say from right to left, polarlzing
that part which embraces the armature, say
south; thence to the upper commutator
brush and through the armature polarizing
that portion Of the armnture In advance of
tie field magnet just noted north aud the
remaining half OF said armature In adv nee
of the other field magnet SOUTH finally
passing from the armatlre to the lower
cCmmutator brush and through the remain
ing field magnet from left to right to the
outgoing post, thus polarizing this field
magnet north.
The current then returns to the dynamo
iId passes through its field magnets and
almature to the starting point, thus running
In u Cilclc.
Now this action OF polarzing the motor
fCld magnets aud armature sets up mag
Ittic field In the space between the field
magnets and causes the armature To turn
iis upper half toward the first field magnet
and It's lower half toward the second field
magnet. Magnetic action aud reaction
takes place Just rs In the dynamo, before
described, until the armaturo has attained
maximum speed of rotation.
1t will, OF course, be clear, then, that as
the aImature of the motor revOlvcs II Will
tend 10 set up current over the line In q
reverse direction from that set up by the
dynamo furnishing the current, since IL in
turn acts as q dynamo.
This back flow of electricity Is called
Countcr-electro motive force, aud exists
IN all electrical devices which do work or
utilize electrical energy to useful purpose.
If the motor Is an exact duplicate OF the
dynamo, and the latter Is driven at maxi
mum speed for It's capacity, the motor, af-
ter attaining maximum speed, VIII gener-
ate almost rs much counter electricity
as the dynamo, but running through the
circuit as before noted IN an opposite dlrec-
tlon, so that II galyanomcter Is placed IN
the circuit but little current can be detected
When, however, the motor is called upon to
carry q load, rs by connecting the armaturo
shaft with pulley aud belt 10 some ma
chine to be operated, the counter-eectrO
motive force Is overcome or rather the
power developed in the motor armaturc Is
then translated into another kind OF en-
ergy, aud the dynamo furnishes current
then for such purpose, which will be
strongly indicated In the circuit.
Motors are classified Just as are dynamOs,
into series wound, such a. Is ubuye de
ecrlbcd, aud shuut wound, where the field
magnets are onorgized hy "a by-puth or
shunt conductor, while the available work.
ing current Is taken direct 10 the armature
by the commutator brushes,
An essential difference between the two
fOms lies In the fact that the series wound
machine will reverse the direction Of ruta-
tlOn Of its aTmaturc On reversing the dlreC.
tiOn Of the current In the Hue while the
shunt wound machine will always rotate
its immature IN the same direction regard.
less OF tue direction of the current.
Motors have all the peculiar character.
istics OF dynamos concerning the shape aud
winding Of the armaturo aud hcld mag
nets, hence, ali that has been said Ia this
respect upon dynamos In our previous arti'
Gle applies here.
We might remark in passing, however,
that II was the discovery Of the rvacilnuary
principle Of the dynamo which made the
electric motor also q possible success.
The electric motor like the dynamo, Too