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

page_text: Date of Application, 11th Mar., 1893-Accepted, 15th Apr., 1893
COMPLETE SPECIFICATION.
Improvements in and relating to Alternating Current Electric
Motors.
We, ROBERT LUNDELL and EDWARD HIBBERD JOHNSON, both of
Number 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 particularly to improvements in that type of alternating
current motors designed to run in synchronism with well known forms of alternating
current generators.
To this end it consists in the novel method of and means for bringing about such
synchronism as hereinafter fully described.
For a full, clear and exact understanding of the invention such as will enable
others skilled in the art to which it most nearly relates to construct and use the
same, reference is had to the following description and to the accompanying
drawings, in which :-
:-
Figure 1 is a diagrammatic view of the entire apparatus showing also the switch
and circuit connections to the current mains.
Figure 2 is a sectional view taken through the body of the motor on the line x—x,
Figure 1.
Figure 3 is a part side elevational view of the motor illustrating the armature in
an advanced position from that shown in Figure 1.
Figure 4 is a similar view showing the armature in a third or still further
advanced position from that shown in Figure 3.
Figure 5 is a diagrammatic view illustrating the current phases and is also
designed to aid in describing the magnetic changes which take place in the field
magnet cores as the armature passes through the several positions under the
changes of current phase attributable to the entire structure.
Prior to this invention various well known methods and apparatus for
synchronizing alternating current motors and generators had been devised.
Electrical and mechanical motors had been utilized to rotate the armature of the
motor until it reached the point of absolute synchronism, after which the power
thus applied was discontinued.
Electrical impulses have been transmitted over the line to such motors by
various methods, and utilized to the same end.
Currents of divided phase had been used locally to establish a rotary magnetic
field in the field magnet poles by the presence of choke coils, resistances,
condensers, &c., the retarded or advanced phase currents thus utilized being
discontinued after synchronism was reached. In the invention herein described
the generic principle of divided current phases established locally or at or near the
motor itself is made use of by causing one set of such phases to set up magnetism
in the field magnet poles of the field magnet and the second or retarded set to so
vary the relative magnetic effect of the first or established magnetic conditions
that the magnetic equilibrium is disturbed in said poles and kept so continuously
disturbed, until the armature assumes a velocity of rotation in synchronism with
the rotary magnetic field of the field magnet poles.
This is accomplished by successively increasing the magnetic effect in the field
magnet poles on one side of said poles and in advance of the armature poles as they
rotate or tend to rotate and by simultaneously decreasing or nullifying the like
effect on the rear side of these poles.

page_text: Referring now to the drawings in detail in all of which like letters of reference
represent like parts wherever used.
F is a laminated ring like field magnet core having internally projecting
poles N N, SS, &c., split or divided in order to afford space for overlapping
synchronizing coils M' M. The armature A has also a laminated core provided
with lateral grooves, notches or holes in its face located at equal distances apart so
as to divide the face into ten pole pieces to correspond with the like number of
field poles.
In these grooves are located conductors E E of non-magnetic material and low
conductivity, their ends being connected together at the ends of the core by
similar conducting rings R R so that the entire system constitutes a multiple arc
low resistance set of conductors closed on themselves and lying near the face of the
armature.
This armature is bound together firmly by these conductors and is supported by
a spider S adapted to receive an axis not shown.
B and B are binding posts connected directly to the current mains not shown
but running to a distant point where the generator is located.
Sw is a switch arm pivotally connected to the binding post B₁ and having on
its rear or outer side a projection or lug l and e, e', e² are contact points with which
this conducting switch arm is adapted to contact; the lug only resting on the
contacte when the switch arm is in the position shown in dotted lines.
C² is a converter of well known form constructed so as to give as great a magnetic
lag as possible to the secondary current phases for a reason which will be described
in connection with the description of the mode of operation.
The primary coil P is connected directly to binding post B and contact by a
conductor w and the secondary coil S₁ by a conductor w² to the contact e² and in
series through a set of field magnet coils M¹ M', &c., and finally by wires w² and w¹
to binding post B'.
The binding posts B and B are also connected directly to the field magnet
coils M, M &c., in series.
These coils, M, M, &c., constitute the primary or power imparting source of
energy and their arrangement and circuit connections individually with the motor
are as is usual in this generic type of motors, the windings being as is indicated so
as to set up the polarities shown and bring about the usual alternating magnetic
field and in the well known way
This invention consists in so disturbing the magnetic equilibrium of these
alternating field poles that the armature which under normal conditions with such
a field would stand still will now when placed under the new condition of affairs
tend to rotate and this tendency continue until synchronism is effected after which
the disturbed condition of affairs may be discontinued and the armature allowed to
rotate in a manner at once appreciable to those skilled in the art. This effect is
brought about by locating and so winding the coils M M' &c., with relation to the
coils M M &c., that the retarded current phases due to the converter C³ will increase
the magnetic effect in advance of the poles a, b, c &c., of the armature and diminish
or nullify the like effect in the rear thereof.
To do this the coils M' M' are wound in reverse direction and about alternate
or overlapping pairs of poles with the coils M, M, &c., as shown in Figure 1.
The operation is as follows :-
The switch Sw having been placed on contacts e, e¹ and e² the current impulses
find two paths at B and B'.
First by wires w w and field maguet coils M, M, &c., and second by wires w', w',
and the primary coil of converter C².
The direct impulses passing through field magnet coils M, M, &c., set up the
usual alternating magnetic field, and current phases flow resembling C on opposite
sides of the line of no potentials L L, Figure 5.
The impulses induced in the converter C³ therefore set up in the secondary coil Si
conductors and synchronizing coils M, M &c., a secondary set of impulses

page_text: differing in phase an amount dependent upon the inefficiency of the converter and
corresponding to the phases indicated at C in dotted lines, see Figure 5.
For a clear understanding of the magnetic changes which take place for a
complete current phase through the coils M M and a corresponding divided or
secondary phase in the coils M' M', reference is had to Figures 1, 3 and 4 in
connection with Figure 5, the polarities indicated upon the poles of the field
magnet cores opposite the corresponding armature poles a, b, and c as indicated in
Figure 1 agree with the current phase indicated in Figure 5 on the curve C at
the ordinate one. At this time the divided or induced phase corresponding to the
curve C has just commenced to exist and at the next instant of time when the
potential of the two phases is substantially equal as indicated at the ordinate
three, the united effect of the ampere turns through the coils M due to the current
phase C and the induced or retarded current phase C¹ in the coils M¹ is such that
the polar conditions of the corresponding parts assume the relation shown in
Figure 3; that is to say, the south pole to the right and in advance of the tooth a
has been strengthened, while the corresponding south pole in the tooth to the left
has been weakened, thereby causing the armature to advance to the position shown
in Figure 3 and the magnetic lines of force to assume the direction shown at m.
At the next instant of time the secondary or induced phase has assumed the
position shown by the ordinate four on the curve C¹ and this secondary phase
exerts the entire magnetizing influence of the field poles while no influence is
exerted by the primary impulse, as will be clear on examination of Figure 5, the
curve at this time crossing the line L L of no potential. This last condition causes
the armature to advance to the position shown in Figure 4 so that the tooth a is
now directly beneath the poles S S as there shown.
It will of course be understood that for the reverse phase and its corresponding
divided or secondary phase below the line L L of no potentials a repetition of
results will follow, and hence the armature will continue to rotate.
The armature therefore follows this continned advanced distortion or magnetic
disturbance and after it has reached the point of synchronism the switch is turned
to the position shown in dotted lines Figure 1, the converter cut out and the motor
allowed to run as synchronous motors usually do.
The drawing shows a ten pole motor. Suppose the generator to be a well
known Westinghouse sixteen pole machine and running at 1,000 revolutions per
minute, thus giving 1,600 alternations. It will be apparent that synchronism will
be attained when the armature reaches a speed of 1,000 revolutions per minute.
The relative proportions of the windings or ampere turns of the coils M M
and M M will of course be such as the necessities of the case demand, such
matters being within the skill of any electrician versed in the building of this type
of apparatus.
The switch Sw and circuit connections are preferably enclosed in a box or
casing closely adjacent to the motor, it being desirable to have the operation of the
motor under control of the user thereof although this apparatus may be located
at a distance if desired.
It is to be understood that more than one transformer may be used in the
manner herein shown and described, it being understood that when additional
transformers are used the field magnet poles would be again divided into corre-
spondingly greater numbers of teeth and the transformers adapted to give
proportionate varying lag. Other devices than transformers for varying the
current phases may also be used, such for instance as choke coils, condensers and
the like, in which event the windings of the synchronizing coils with relation to
the main coils M M would be arranged to suit the polarities of the divided phase
currents.
The usual well known starting resistance coils for varying the electro-motive
force of the current supply would be used in connection with the switch and its
operative connections to the apparatus above disclosed.
It is believed to be broadly new to utilize alternating currents of different phase

page_text: to intensify the field inagnet poles of an alternating current motor at one or more
points and to simultaneously weaken or nullify the magnetism thereof at one or
more different points so that an armature under the influence of such magnetic
distortion will tend to rotate and the claims hereinafter made are commensurate
with the application of this generic principle regardless of the means used.
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 synchronizing an alternating current electric motor
with an alternating current generator to which it is electrically connected consisting
in intensifying the field magnet poles at various points and in simultaneously
diminishing or nullifying the magnetism thercof at other points whereby the
armature is subjected to a distorted magnetic influence.
2. The described method of synchronizing an alternating current electric motor
with its connected source of current supply consisting in setting up divided current
phases, then causing one set of such phases to magnetize the field magnet cores
and the other to alternately strengthen and weaken the effect of the first set
whereby magnetic distortion ensues and the armature is set in motion.
3. The described method of causing the armature of an alternating current
electric motor to move, consisting in subjecting its magnetic poles to the influence
of two sets of current phases which alternately strengthen and weaken the field
magnet poles in advance of them.
4. The described method of causing the armature or movable part of an
alternating current electric motor to be set in motion under the influence of
alternating currents of electricity consisting in dividing the propelling currents
into currents of double phase utilizing one set thereof to magnetize the field
magnet poles and the other to alternately strengthen and weaken the effect of the
first set, thereby creating a distorted magnetic field tending to continuously advance
the armature.
5. An alternating current electric motor having its field magnet cores wound
with differential coils in combination with means for setting up and conveying to
the sets of coils currents of differing phase, substantially as described.
6. An alternating current electric motor having two sets of differentially wound
field magnet coils in combination with means for setting up two sets of current
phases and circuit connections for conveying one set of phases through one set of
coils and the other set of such phases through the remaining coils, substantially as
described.
7. An alternating current electric motor having one set of field magnet coils
wound in one direction around each field magnet pole and the other set of such
coils wound in the same direction around one half of each pole and in a reverse
direction around the remaining half of each pole, substantially as shown and
described.
8. An alternating current electric motor having its field magnet coils in circuit
with a source of current supply and a second or independent set of synchronizing
coils in circuit with the secondary of a converter the primary of which is in circuit
with the same source of current supply, substantially as described.
9. An alternating current electric motor a converter a source of alternating
current supply and circuit connections between the source of supply, the converter
and the motor, whereby the secondary or induced currents are utilized in starting
the motor, substantially as described.
10. A source of alternating electric currents an alternating current electric
motor operatively connected thereto, a converter having its primary connected to
the same source of current supply and its secondary to the motor, whereby the
induced impulses may be utilized for starting the motor, substantially as described.
11. An alternating current electric motor having an armature provided with a
given number of poles and a field magnet provided with a like number of poles

page_text: divided each into two or more parts or projections, substantially as shown and
described.
12. An alternating current electric motor having an armature provided with a
given number of poles and a field magnet provided with a like number of poles
divided at the ends next the armature core in combination with two sets of field
magnet cores which overlap each other, substantially as shown and described.
Dated this 11th day of March 1893.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicants.