Improvements in Armatures for Induction Motors.
Year: 1896

page_text: Date of Application, 11th Feb., 1896-Accepted, 21st Mar., 1896
COMPLETE SPECIFICATION.
Improvements in Armatures for Induction Motors.
I, ABE LINCOLN CUSHMAN, of Concord, in the County of Merrimac, and State of
New Hampshire, United States of America, Electrician, do hereby declare the nature
of this invention, and in what manner the same is to bo performed, to be particularly
described and ascertained, in and by the following statement. :-
My invention relates to armatures for induction motors which combine resistance
coils for securing a good starting torque.
The objects being to provide a good starting torque, and to control the speed and
power of motors of this character in as simple a manner as possible.
To this end my invention consists essentially in providing an armature with coils each
containing one Gerinan silver or high resistance bar, and one copper bar connected in
series, all said bars being active elements in the coils; and means for cutting out the
German silver or high resistance bars.
As far as am aware my present invention differs from any other in which
resistance is employed, for the reason that, my resistance forms part of the regular
armature windings.
The accompanying drawings show an embodiment of my invention: Figure 1, is a
perspective view of my improved armature, showing a portion of the short circuiting
sleeve broken away:
Figure 2, is a broken elevation of the laminated core in which are shown the grooves
to receive the coils.
Figure 3, is a detached broken plan view of one of the windings showing means for
cutting out the resistance :
Figure 4, shows the connections for one coil winding at that end in which the
resistance is placed:
Figure 5, is a detached broken elevation of a disk which carries the contact points or
plates for cutting out the resistance:
Figure 6, is a broken elevation of the laminated core showing the connection for one
of the windings at that end opposite to that shown in Figure 4.
Similar reference letters denote corresponding parts throughout the several views.
A, is a laminated core having grooves B-C, in which are placed the coils or
bars Dd and E, which are connected in sets as shown; each pair D-d being
connected with a bar E, distant about one-fourth the circumference of the core, which
forms one coil or winding.
At one end the connection is made as seen in Figures 1 and 3, and 4, and the other
as seen in Figures 3 and 6 and by dotted lines in Figure 1. The coil bar E at one
end, is connected to the coil bar d, by the end connections F-f, the bar F being
composed of copper, and the bar f, of German silver or other high electrical resistance,
and soldered, or otherwise firmly secured, while the opposite end is provided with an
end connection G, which is formed of copper, and connects one end of both bars D-d
with the bars E, direct, thus forming a coil or winding comprising within itself a
resistance, as has been shown.
Now, in order after starting, and having attained the desired speed, to cut out the
resistance, I attach one end of a bar H, to that end of a bar D which is adjacent to
the resistance f, carrying it's free end to a suitable ring or collar %, (composed of
insulating material) to which it may be attached as shown.
The German silver coil or bar d, being connected by the connections f-F and G,
with the coil bars D-E, a resistance is combined with each coil of the armature, and

page_text: to cut out the resistance after starting the motor it is only necessary to bring the
connections F-H at one of each coil, in contact, and a simple means for accomplishing
this is shown in the drawings and consists in the contact points or plugs I, attached
by screws or rivets i to a ring J, formed of some insulating material and carried on a
collar K, which may be mounted and arranged to move horizontally upon the arbor
or shaft L, of the armature.
It is obvious that the free end of the bar H, may be carried to a convenient point
for contact with the bar F in other ways than are shown herein, and so also may the
contact point I, which is shown for making the electrical connection between the
connecting bars F-H, be otherwise arranged, and still retain the essential features
of my invention, hence, in order to avoid complications and to present the important
points of my invention in as clear a manner as possible, I have shown and described
but one means of reducing my invention to practice.
The collar K, may be moved toward and away from the bars F and H,
(automatically if desired) by any suitable means applied to it's groove k, the latter
being shown in Figures 1 and 3.
The general features in the construction of my improved armature may be briefly
expressed as follows:
The core is provided with longitudinal grooves formed deep and shallow alternately,
and coil bars placed therein,--the shallow grooves containing one bar and the deeper
grooves containing two bars, one being of copper and the other of German silver or
any higher resistance-insulated from each other and connected at one end by
copper and at the other by copper and German silver bars as follows: To one end
of the German silver bar d is attached a German silver strip the opposite end of which
is secured to one end of a copper strip F, so as to form a good electrical contact; the
opposite end of the said strip F is connected to the bar E, which forms the circuit
through the German silver bar d, copper strip G, copper bar E, copper strip F, and
German silver strip f, in starting the motor.
When the desired speed has been attained, the German silver bar d and German
silver strip, is cut out of the circuit, which is then formed through the copper
bars D-E, and their copper connections F-G-H, by short-circuiting the
strips F-H by any well known mechanism, or by such as shown at I---J, in
Figure 5.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
I claim is
1. In an armature for induction motors, a coil composed of an active high resistance
portion and two or more low resistance portions, the high resistance portion and one
of the low resistance portions being constantly in series, substantially for the purpose
described.
2. In an armature for induction motors, coils composed of an active high resistance
portion and two low resistance portions, the high resistance portion and one of the
low resistance portions being constantly in series, and a switch so arranged as to
connect the second low resistance portion in multiple with the high resistance
portion.
3. An armature for induction motors having coils or windings composed of active
high resistance portions and low resistance portions, one of the high resistance portions
and one of the low resistance portions being constantly in series, and suitable means
for connecting the low resistance portions in multiple with the high resistance
portions.
Dated this Sixth day of January AD 1896
ABE LINCOLN CUSHMAN.