Improvements in and relating to Alternating Current Electric Motors.
Year: 1893

page_text: Date of Application, 11th Mar., 1893-Accepted. 22nd Apr., 1893
COMPLETE SPECIFICATION.
Improvements in and relating to Alternating Current Electric
Motors.
We, ROBERT LUNDELL and EDWARD HIBBERD JOHNSON, both of No. 44
Broad Street, New York City, New York, United States of America, Electricians,
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 :-
This invention relates especially to that type of apparatus known in the art as
alternating current electric motors, and it has for its objects,
First The construction of a motor of this type which shall be self-starting either
with or without a load:
Second-The regulation of the magnetic torque or pull upon the rotary or
movable part in accordance with the demands upon that part in the application of
power:
Third The provision of means for reversing the direction of the rotary or movable
part as desired:
Fourth The accomplishment of any and all of the results which are necessarily
attributable to the methods of operation and apparatus hereinafter described.
The aforesaid objects are accomplished by the practice of the methods and with
the aid of the improved apparatus hereinafter described and fully illustrated in the
accompanying drawings in which
Figure 1 represents a side elevational view of a motor embodying the principles
of this invention, the field coils of said motor being connected directly in circuit
with a pair of current mains.
Figure 2 is a plan view thereof, the field coils and cores being shown in section.
Figures 3 and 4 are diagrammatic views of the same machine illustrating respec-
tively the operative condition of affairs in the armature circuit attributable to
different locations of the current collecting brushes.
It is a well-known fact that if an electric conductor be closed upon itself and
located in the magnetic field of the core of an electro-magnet through the coils of
which alternating currents of electricity are passed, this closed circuit will tend to
be repelled from the pole of the magnet so long as it remains in a plane parallel
with that pole or at right angles to the magnetic lines of force and also that if said
closed conductor be slightly tilted, in any direction it will immediately tend to set
up a motion about the axis around which it is tilted and to place itself in a plane
parallel with the axis of the core or coincident with the magnetic lines of force
emanating therefrom. In other words the instant that this closed circuit is tilted
about a given axis, the magnetic lines of force act inductively upon the conductor
and a certain amount of energy is consumed in causing the conductor to change its
angular position with relation to the magnet pole. Upon the application of this
generic principle the invention is based.
We are aware that it is not broadly new with us to utilize the inductive effects of
one or more stationary field magnet coils upon a rotary armature provided with
short circuit connections between the opposite ends of any single coil or single pair
of coils in such manner that the armature is caused to rotate under the application
of induced currents upon such coil or coils and that as the armature rotates said
coil or coils will tend to be placed in a plane parallel with or coincident with the
magnetic lines of force. Although the invention involves the application of this
generic principle, we make no claim broad enough to include such a structure or
mode of operation.
This invention will be fully understood by reference to the accompanying
drawings in all of which like letters of reference represent like parts wherever used.

page_text: ww are current mains runuing to a distant alternating current generator not
shown, said mains being connected directly by a conductor w¹ to the field magnet
coils F F of this improved motor, C being the laminated field magnet core thereof
having inwardly projecting pole pieces PP.
A is the armature made of laminated toothed discs carried by the axis A¹ and
wound as shown, after the manner of a Gramme armature, each section of which is
connected to an individual commutator strip in the usual way.
B B are stationary current collecting brushes permanently secured in alignment
with the central or axial line of the field magnet poles P P as shown in Figure 1,
their inner ends resting directly upon the commutator, while their outer ends are
connected to shunt circuits S S of low resistance, which in turn are connected to
the outer ends of a pair of independent movable current collecting brushes B₁ B₁
carried by the usual form of brush rocker or holder, not shown, but adapted to
permit of the rotation of said brushes into any position. These movable brushes B₁ B₁
and their rocker or carrier are located just outside the fixed brushes B B so that
they may be rotated to any desired position and in either direction at will, as will
be apparent on inspection of Figure 2.
The operation of the apparatus is as follows:
Suppose the brushes B B' in Figures 1 and 2 be shifted to the left until they
are parallel with or in the same plane with the brushes B B. Under this condition
of affairs if an alternating current is set up in the mains war and the field coils F
through the conductor w, the armature A would not rotate inasmuch as the inductive
effect upon all of the coils on both sides is identical, none of them being short
circuited. Should the brushes B¹ B now however be shifted forward in the
direction towards which they appear in Figures 1 and 2, the instant that they rest
upon the next commutator sections in advance of those upon which the stationary
brushes B and B are resting, the first coil of the armature A on the left above the
brush B will be short circuited through the low resistance conductor S¹ and in like
manner that coil of the armature on the right below the corresponding brush B
will be short circuited through the low resistance coil S.
By virtue of these two short circuited coils therefore, there is at once set up in the
armature A, a tendency to rotate from right to left. As the brushes B' B' are
advanced in the direction shown in Figures 1 and 2 the successive coils of the
armature A above the left hand brush B and the like coils below the right hand
brush B will be short circuited through the low resistance conductors S' and S,
thus placing an increased number of short circuited coils under the influence of the
field poles PP, a maximum effect being reached when those brushes stand
approximately at right angles to the brushes B B. By rotating the brushes B¹ B₁
in the reverse direction from the starting point it is apparent that the armature
will rotate in the opposite direction, thus furnishing a ready and efficient means of
changing the direction of the applied power.
We have illustrated in Figures 3 and 4 the relative torque effects due respectively
to the location of the movable brushes in the first instance at a point about thirty
degrees from the stationary brushes, and in the second instance at a point ninety
degrees distant from said brushes, the relative effects being indicated by the shaded
surfaces upon the armatures A, those shaded portions representing also the actual
proportion of armature coils which are short circuited by the brushes B B, B¹ B
through the coils S and S¹ for the positions above indicated.
It will be understood therefore that by this method of setting up an increasing
inductive field in the armature through the agency of short circuited coils, we are
enabled to vary the magnetic pull or torque in accordance with the demand or load,
and also that we obtain a self starting armature in which the means of applying
the inductive effects are adapted not only to vary the current supply in accordance
with the load to be moved but also to avoid damaging effects upon the machine
itself by virtue of the choke coil action of the motor which is obvious in view of
the nature of its construction.
We do not limit ourselves to any special structure of armature such as that

page_text: herein shown and described. In fact we should prefer to use what is known as a
cylindrical or barrel type of armature core with laminated toothed discs, as with
such a core a more perfect magnetic circuit would be maintained between the field
poles.
We have herein illustrated and described the structure as having an armature of
the Gramme type for the reason that the circuit connections can be much more
easily illustrated with such a type of armature.
Nor do we limit ourselves to the special form of two pole motor herein shown and
described, it being apparent that the novel principle hereinbefore described may be
practised equally as well with multipolar machines. With machines of the multi-
polar type however there would be required two pairs of brushes for each pair of
poles, unless the armature be of the well known cross-connected type in which event
there need be only two pair of brushes for any number of poles."
In fact existing well known types of electric motors may be adapted to practice
the novel methods herein described and still not depart materially from the generic
application of the novel principle hereinafter claimed by us. In other words the
claims are to be construed broadly as embracing the application of the principles
herein before ennunciated to existing types of electric motors without regard to their
individual structure.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed, we declare that what we
claim is :-
1. The described method of operating an alternating current electric motor con-
sisting in varying the inductive effect upon the armature by short circuiting the
armature coils in sequence until the desired torque or pull is attained.
2. The described method of causing the armature of an alternating current
motor to start unaided, consisting in short circuiting certain of the coils thereof in
sequence until the desired speed and torque is reached.
3. The described method of regulating the magnetic conditions of the rotary
part of an alternating current electric motor in accordance with the speed or load
consisting in setting up increased magnetic effects in the rotary part as the speed or
load is increased.
4. The described method of regulating an alternating current motor consisting
in maintaining the magnetic effect of the field constant and in varying the magnetic
effect of the rotary part to accord with the speed or load.
5. The described method of operating an alternating current electric motor con-
sisting in shunting the armature coils in sequence on opposite sides adjacent to the
opposite field poles.
6. The described method of operating an alternating current electric motor con-
sisting in maintaining the field magnet effects constant and in varying the secondary
or induced effects of the same on the rotary or movable part by short circuiting in
sequence the coils of the rotary or movable part as they approach the axial line of
the field magnet coils.
7. An alternating current motor having its field magnet coils in a closed circuit
and a rotary or movable part provided with a series of independent coils having
their ends united to a commutator in combination with means for shunting the coils
in sequence, substantially as described.
8. An alternating current motor provided with a pair of stationary inducing field
coils and a movable or rotary armature provided with a series of coils having their
free ends attached to a current collecting device in combination with a fixed and a
movable pair of current collecting brushes and shunt circuits connecting said
brushes as described.
9. An alternating current motor having a fixed field magnet and a rotary or
movable part with independent coils connected to a current connecting device in
combination with a fixed and a movable current collecting brush and a conductor
joining said brushes as described.

page_text: 10. An alternating current motor having a pair of current collecting brushes,
one fixed and the other movable with a conductor connecting said brushes; the
movable brush lying in a different plane from and adapted to be rotated past the
fixed brush as described.
11. The described method of reversing the direction of rotation of the armature
in an alternating current motor consisting in shifting the current collecting brushes
to different positions with relation to the inducing magnetic field.
12. In an alternating current motor two fixed and two movable brushes connected
in pairs, the movable brushes being located in a plane substantially parallel with
the fixed brushes and adapted to rotate past them in either direction at will,
substantially as described.
13. An alternating current motor having stationary and movable current
collecting brushes bearing on a commutating device, the movable brushes having
rotation about the fixed brushes in either direction at will, substantially as
described.
14. An alternating current motor having two or more field magnet poles, a
rotary armature having a series of coils connected to a common current collector, a
single pair of fixed current collecting brushes and a like pair of movable current
collecting brushes and shunt conductors joining said fixed and movable brushes in
pairs as described.
15. An alternating current motor having two or more inducing or field magnet
poles, a rotary armature having a magnetic core surrounded by a series of secondary
coils connected to a common current collecting device, a pair of fixed or stationary
current collecting brushes located in alignment with the axial centre of each pair of
inducing poles and a corresponding pair of movable current collecting brushes for
each pair of poles, said fixed and movable brushes being connected together in pairs
as described.
Dated this 11th day of March 1893
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicants.