Improvements in Apparatus for Controlling Electric Motors.
Year: 1896

page_text: Date of Application, 7th Jan., 1896-Accepted, 8th Feb.. 1896
QUILL BULD
DIMTRATION.
[Communicated from abroad by BRADLEY ALLAN FISKE, of Hotel Beresfor.!,
New York, United States of America, Lieutenant United States Navy.]
Improvements in Apparatus for Controlling Electric Motors.
1, HENRY HARRIS LAKE, of the Firm of Haseltine, Lake & Co., Patent
Agents, 45 Southampton Buildings, in the County of Middlesex, do hereby
declare the nature of this invention and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement:-
The invention is an apparatus for controlling an electric motor so that said
motor can be caused to run in one direction or the other at a desired speed, or
stopped instantly-and wherein said control is effected by the movement of a single
hand lever, and without the use of resistances interposed in the armature circuit of
the generator which supplies the rantor.
The accompanying drawing is an electrical diagram.
A and B are the positive and negative conductors communicating with any
suitable electrical generator. C is any motor such as a steam engine. D is a
dynamo actuated by said engine. E is the electric inotor, the operation of which
is to be controlled by my apparatus. 1 and 2, 3 and 4, 5 and 6, 7 and 8 are pairs
of contact plates. F is a switch lever having the parts H and I of conducting
material insulated from one another as shown-and suitably pivoted so as to make
contact with said plates as hereinafter described. 9, 10, 11, 12, and 14, 15
and 16 are fixed contact plates disposed in the path of movement of lever F.
Said lever when in central position makes contact with the plate 9. Between the
plates 9, 10, 11, 12 are interposed resistances 17, 18, 19. The pairs of plates 10
and 14, 11 and 15, and 12 and 16 are connected by wires of low resistance as
shown.
The circuit connections in the apparatus are as follows:
One terminal of the field coil of dynamo D is connected by wire 20 to one main
conductor as A. The other terminal is connected by wire 22 to contact plate 12.
The main conductor B is connected by wire 21 to the end G of the switch lever F,
the end being insulated from the part H of said lever. When the end G of
lever F is in contact with any plate as 9, 10, 11, 12, 14, 15, 16 then circuit is
completed from the field coil of dynamo D through one or more or none of the
resistances 17, 18, 19. In this way the said field coil is at all times energized from
the main conductors A, B or line; but this is not essential inasmuch as if desired
said coil may be energized from any other electrical source.
The brush terminals 23, 24 of dynamo D are connected to contact plates 1
and 7.
The terminals of the field coil of the electric motor E are connected by wires 25
and 26 to the main conductors A, B. The armature terminals 27 and 28 of said
motor are connected to contact plates 2 and 3.
Contact plates 1 and 4 are connected together; so also are contact plates 3
and 5, 6 and 7, and 2 and 8. Contact plate 3 is connected also to a separate fixed
contact plate 29. The contact plate 2 is elongated so that the part Hof lever F
when said lever is in central position as represented, makes contact with it.
When the lever F is in the central position shown, the motor is at rest since

page_text: circuit is closed between the brushes 27, 28 from plate 3 to plate 29, throng
part Hof lever F and plate 2; and the circuit also between the brushes of the
dynamo is open.
Assume that it is desired to start the motor to rotate to the right. Lever F is
moved to the right so as to bridge the contact plates 1 and 2 by its arm H and 5
and 6 by its arm I. Circuit is then established as follows:
From brush 23 of dynamo D to plate 7, to plate 6, arm I on lever F, plate 5
plate 3, brush 28 of armature of motor E and through the armature coil to the
other brush 27, to plate 2, arma Hun lever F, plate 1, plate 4 and so to the
other brush 24 of dynamo D. The field coil of the motor E being energized
from the main conductors A, B or any other source and a current from brush 28
to brush 27 being established in the armature coil, the armature rotates (say) to
the right.
If it be desired to cause the motor to turn to the left, the lever F is moved to
bridge the contact plates 7 and 8 by arm H and 3 and 4 by arm 1; circuit is then
established as follows:
From brush 23 of dynamo, to plate 7, armm H on lever F, plate 8, plate 2,
brush 27 of motor E, through the armature coil to brush 28, plate 3, arm I on
lever F, plate 4 and so to brush 24 of dynamo. The current is then established in
the armature coil from brush 27 to brusli 28-and said armature then rotates in the
reverse direction.
The object of the contact plates and resistances 17, 18, 19 interposed in the field
circuit of the dynamo D is to graduate the speed of rotation of the motor E. Thus
assume that the lever F being moved to the right, still remains on plate 9. The
circuit from the dynamo will continue to proceed through all of the resistances 17,
18 19 to said plate 9, to end G and so to conductor B. If the end G be still
further moved to the right to make contact with plate 14, then only resistances 17, 18
will be in circuit, and when finally said end makes contact with plate 16 none of the
said resistances will be in circuit. The same result happens when the lever is moved
to the left, all of the resistances being in circuit so long as it is in contact with
plate 9 and none when it is in contact with plate 12.
Hence the further the switch lever F is moved from the central position in one
direction or the other, the less is the resistance interposed in the field circuit of the
dynamo D, the greater the strength of current energizing said coil and the greater
the E.M.F. of the current generated by the dynamo and delivered to the motor E
and hence the greater the speed of the motor.
Therefore the movement of the lever F in one direction or the other determines
the direction of rotation of the armature of the motor E, while the extent of move-
ment of said lever at the same time determines the speed of said rotation. The
final result is complete control of the motor by means of the single lever F. If that
lever be moved to the right, the motor rotates (say) to the right-and the further
the lever is moved the faster the motor runs-so also if the lever be moved to the
left and to stop the motor instantly, the lever F is shifted to its central position
as shown, when armature circuit of dynamo is broken and the circuit between the
motor brushes 27 and 28 is closed.
In place of the arrangement of contact plates and resistances shown in Fig. 1,
I may use that shown in Fig. 2. Here instead of a single elongated contact plate 9,
two contact plates 9 and 13 are used. When the end G of lever F touches either
of these plates, all of the resistances are in circuit, but when it is in its central
position as shown the field circuit in the dynamo is broken.
It will be observed that I use no resistances in the armature circuit of the dynamo
or motor, and hence expend none of the energy of the current generated by the
dynamo in overcoming the heavy resistances which ordinarily would be required to
reduce or vary the E.M.F. applied at the brushes 27 and 28. Nor do I require
two independent devices one to vary the E.M.F. of the current and the other to
reverse the current in the motor-both results being simultaneously accomplished
by the simple movement of the lever F. The contact plates 1, 2, 3, 4, 5, 6, 7, 8

page_text: are made long enough so that the lever will touch them when placed on contact
plates 9 to 16, except when in its central position.
I find it advantageous in some cases to carry the armature circuit of dynamo D
around the field, thus rendering the dynamo compound wound. In the arrangement
shown in Fig. 1 the field of dynamo D is always in circuit with the main conductors,
or other source of electricity, so that said field is always in energized state. The
advantage of this is that the magnetic lag and impedance in the field coil, which
occurs on the establishment of circuit therein, are lessened, and the dynamo is ready
at any instant to deliver an effective current.
It will further be observed that the reversal of the current occurs when the
resistances 17, 18, 19 are in circuit, and always when the voltage is low, so that the
danger of burning contacts or other injury incident to the sudden reversal of
the high E.M.F. is greatly diminished.
Having now particularly described and ascertained the nature of the said inven-
tion, and in what manner the same is to be performed, as communicated to me
by my foreign correspondent, I declare that what I claim is:-
1. In combination with a dynamo and an electric motor actuated thereby, an
apparatus for controlling said motor, having a reversing switch disposed in the
armature circuit of said dynamo and combined with a rheostat to regulate the
strength of the dynamo field.
2. The apparatus for controlling an electric motor, constructed and arranged
substantially as herein shown and described.
Dated this 7th day of January 1896.
HASELTINE, LAKE & Co.,
45 Southampton Buildings, London, W.C., Agents for the Applicant.