Improvements in Alternating Current Motors.
Year: 1898

page_text: Date of Application, 1st Mar., 1898-Accepted, 20th May, 1898
COMPLETE SPECIFICATION.
Improvements in Alternating Current Motors.
I, WILLIAM STANLEY, of Dawes Avenue, Pittsfield, in the County of Berkshire,
State of Massachusetts, United States of America, Electrical Engineer, do hereby
declare the nature of this invention and in what manner the same is to be per-
formed to be particularly described and ascertained in and by the following
statement:
My invention relates to a novel type of induction motor, to be operated by phase-
differing alternating currents. It is constructed with a single primary element
or field-magnet structure, and a single secondary core wound with closed coils,
and hence differs from known motors of the two-field type, the primary member
and secondary circuit or circuits are so arranged that a magnetic flux of given
phase relation induces current in the secondary and this current is acted upon
dynamically by magnetism of a different phase to produce torque in the manner
more fully explained hereafter.
In the accompanying drawing, Figs. 1, 2, 3, 4 and 5 illustrate a number of
modified forms in which the invention may be embodied.
In Fig. 1, the fixed poles N, S, and connecting yoke a, form part of a magnetic
circuit for magnetism of one phase while poles N 1, S1, N and yokes b and c
form part of an independent magnetic circuit for magnetism of a different phase.
The secondary member is inductively related to all the phase-differing primary
fields and the wire is so disposed that the current induced by the action of one
field is acted upon dynamically by one or more of the fields of different phase.
The motor here illustrated is assumed be of the two-phase type, and hence
the poles N, S, may be wound with coils in one branch de, of a quarter-phase
supply circuit, and the poles N 1, S1, N with coils in the second branch of the
circuit fg. Any other desired means, however, may be employed for maintaining
the phase differing magnetic fluxes, many suitable arrangements being now known
to engineers. The magnetic circuit through the poles N 1, $1 N is preferably
divided, as shown, so that three pole faces are presented to the secondary element
in order to permit a more symmetrical disposition of the secondary conductors.
In this case the entire flux passes through the pole $1 and one half of the flux
through each of the poles N 1 N", so that the total flux is symmetrically disposed
with reference to the secondary circuits when the latter are arranged as shown.
The secondary member of the motor B consists of a single core and coils wound
thereon in any well known manner providing closed electric circuits. In the
diagram three coils are shown, numbered 1, 2, and 3. With the motor at rest
and the parts in the position shown, the coil 1 receives the flux through poles N
and S and is in the position of maximum induction with reference to these poles,
while the current thus induced in flowing through that part of its circuit which
is adjacent to pole $1 is acted upon by the phase-differing magnetism dynamically
to produce torque. In the same way the fluxes threading the coils 2 and 3 from
poles N 1, S1, generate currents which are acted upon dynamically by the
poles N, S, and the parts are all so arranged that the torque effects produced by
the different currents and magnetic fluxes are cumulative. The motor will there-

page_text: fore be subjected to a starting torque, and will start and run under load. After
the motor has started from a position of rest, the actions become more complex
than those explained above, as each coil is subjected to induction due to the varia-
tions in the primary fluxes, and also to induction due to the fact that in its rotation
it cuts the line of force emanating from the pole pieces. The result is, that the
machine tends to run up to synchronism only, and reaches that speed only in the
theoretical case in which there is no load of any nature and no losses. In practice,
the motor "slips" slightly from synchronous speed, the amount of the slip depend-
ing on various causes, as the amount of the load and the resistance of the armature
or induced winding.
I have shown in this instance the secondary member wound with three coils,
in order to clearly illustrate the essential features of the invention, but in practice
the number and connection of the secondary coils are capable of many modifica-
tions, as will be readily understood. In full lines independent cores for the phase-
differing magnetic circuits are indicated, but in dotted lines I have shown that the
cores may be united in a common ring. In many cases the latter will be prefer-
able from a mechanical standpoint. So far as the operation of the motor is con-
cerned, either construction may be employed.
In Fig. 2 an arrangement is shown very similar to that already described, except
that the poles in each phase group are multiplied, multiplying the magnetic
fluxes correspondingly. In this case the poles N, S; N°, S°, carry magnetism of
one phase for which there are three paths, and the poles N¹, S¹, Ni, Su, Su, form
the second group in which the magnetism is displaced by a quarter of a period.
These last polar faces are divided into five parts, rather than four, for the same
reason as has been already explained in connection with Fig. 1, the different
groups of poles may, as before, have independent yokes, or a common yoke, as
indicated in dotted lines. Magnetic fluxes having the proper difference of phase
are also maintained in the two groups of poles in any desired way. If fed from
a quarter phase generator, one branch of the supply circuit would include magne-
tizing coils maintaining, at that portion of each period when both of the alternating
currents are positive, north poles at N, N°, and south poles at S, So, while the
second group of poles would have windings receiving currents of the second phase,
and maintaining, at the instant considered, polarities as indicated in the drawing.
Each of these poles alternate in sign, as the supply currents alternate but the poles
marked N of each group are always of the opposite sign from the poles marked S
of the same group.
In this arrangement the secondary member is shown as having seven coils.
With the parts as shown in the diagram it will be seen that coils 1, 2, and 3 have
current and electromotive force induced in them by the poles N, S, Nº, Sº, while
the other half of each of these circuits is acted upon dynamically by magnetism
of different phase from the second group of poles to produce torque. In the same
way coils 4, 5, 6 and 7 are in a position where currents are generated by the
poles N 1, $1 N", S", S", and these currents are acted upon dynamically by
the first group of poles.
In Fig. 3 another form of the invention is shown with the poles grouped in a
different manner. Instead of collecting all the magnetic circuits of each phase
together as in Figs. 1 and 2 each primary magnetic circuit stands by itself and
circuits of the different phases are alternated.
Thus each pair of poles marked N, S, forms a complete magnetic circuit and
the magnetism of all these circuits is of one phase, while the poles marked N 1, S1,
form magnetic circuits, all of which are of a second phase, and alternate with the
first named. In this case, the yokes forming part of each circuit may be indepen-
dent or connected, as indicated in dotted lines, so as to form a common yoke for
all the poles, in the manner now customary in building multipolar alternating
machines. I have shown in this figure a secondary winding of the drum type in
sufficient detail to show how it will be arranged in a commercial machine
Starting, for example, from the point 1, the circuit extends lengthwise of the

page_text: secondary core, then across the end, as indicated in dotted lines, and forward over
the core to observer's end at the point 2, then across to point 3, then back to the
rear end of the core, and so on, as will be understood by engineers, from the
diagram. The wire at the points 1, 2, 3, and 4, forming half of the circuit, is
acted upon by magnetism of one phase from the poles N, S, to generate current,
while the wires at points 5, 6, 7, and 8, forming the other half of the circuit, stand
in such relation to the poles N 1, S1, that the currents thus induced are acted
upon dynamically to produce torque. As the motor moves forward the action is
reversed, current being induced by the magnetism of poles N1 S1 and these
currents being acted upon dynamically by the poles N, S. I have shown in this
instance only a single secondary circuit, but in practice the winding may be of
any desired character.
In Fig. 4, another modification is shown, in which the poles are grouped as in
Fig. 3, but the magnetic circuit made by the poles N 1, S1, S", is divided in much
the same manner as in Figs. 1 and 2, and for a similar purpose. In this case
the poles marked N, S, are of one phase, and the poles N1, S1, S", of a second
phase. With the secondary winding standing as shown, it is apparent that the
wire at points 1 and 2 receives the induction from the poles N, S, generating
currents which are acted upon dynamically by the poles of the second phase.
Fig. 5 illustrates a form somewhat allied to that shown in Fig. 2, but having a
symmetrical disposition of the field about the armature or secondary member.
The polar projections marked N, S, N, S, represent fluxes of one phase, while
those marked N¹, S', N¹, S¹, indicate fluxes of a different phase. The secondary
winding of this construction is acted upon inductively by one set of fluxes in one
part, while at the same time in another part it is acted upon dynamically by the
other set of fluxes, thus producing torque and consequent rotation of the secondary
member.
It will be seen that the magnetic fluxes in the various forms of my improved
motor shown and described are essentially complanar, that is to say, they present
themselves to the induced member in a common plane, which allows the structure
of the motor to be much simplified. The essential features of my invention reside
in the generation of a plurality of complanar fluxes, each of a simple periodic or
alternating character and fixed in space, each such as might be produced by a
single phase alternating current acting alone on a magnetic circuit, and subjecting
te the influence of these fluxes, dephased among themselves in their time relation,
an induced or secondary member capable of reacting upon them to produce torque.
I also regard it as new, and part of my present invention, to provide a coil, as for
example the coil 1 in Fig. 1, which on one side is in such relation to a magnetic
field as to have current induced in it by the action of such field, and on its other
side is in such relation to another magnetic field as to react thereon to produce
torque.
Another novel feature lies in the use of adjacent or contiguous poles of opposite
signs excited so as to develop magnetism of the same phase, while at the same time
there are presented to the induced member in the same plane one or more magnetic
fluxes of a different phase.
I have illustrated the invention herein as applied only to a multiphase motor
of one type, to wit: a two-phase motor. The application of the invention to other
multphase motors will however be readily understood by electricians.
Having now particularly described and ascertained the nature of my inven-
tion and in what manner the same is to be performed, I declare that what I
claim is:-
1. In a multiphase motor, an inducing member provided with a set of contiguous
polar faces of one magnetic phase, and a set of polar faces of a different magnetic
phase presented to the induced member so that the resulting fluxes are complanar,
each of said sets containing poles of opposite signs, substantially as described.
2. An alternating current motor comprising in combination a single primary

page_text: 1
structure with means for maintaining therein a plurality of simple, complanar,
dephased, nonintersecting, periodic magnetic fields, each fixed in space, and a
secondary member in inductive relation to said primary structure and capable of
relative rotation, substantially as described.
3. In an alternating current motor, a single primary member wound and con-
nected to develop a plurality of dephased magnetic fluxes, in combination with a
secondary member having a core and closed coils or circuits, one or more, arranged
upon the core so that different portions of the same coil or circuit occupy distorted
or unsymmetrical positions with reference to the path of the dephased magnetic
fluxes, such that one portion of any given circuit will be acted upon inductively
by a flux of given phase to generate current, while, simultaneously, another portion
of the same circuit will be in a position to be acted upon dynamically by a flux
of different phase to produce torque.
4. In an alternating current motor, an inducing member provided with a
plurality of polar faces, comprising at least one of each sign, adjacent to each
other and excited in the same magnetic phase with the othe polar faces excited in
a different magnetic phase the polar faces being so placed with relation to each
other that their fluxes are complanar, in combination with an induced member
capable of rotation relatively to said polar faces, substantially as described.
5. An alternating current motor comprising in combination a single primary
member having sets of polar faces, exciting coils inducing non-intersecting,
complanar, dephased magnetic fluxes, each of which is fixed in space and passes
through its own set of polar faces, and a secondary member in inductive relation
to the primary member having a single core and closed coils or circuits, one or
more arranged upon the core, so that different portions of the circuits occupy dis-
torted or unsymmetrical positions with. reference to the different sets of polar
faces, such that one portion of any given circuit will be acted upon inductively
by a flux of given phase to generate current, while simultaneously, another portion
of the same circuit will be in a position to be acted upon dynamically by a flux
of different phase to produce torque, substantially as described.
6. In an alternating current motor, the combination of a multiphase inducing
member, and a secondary member so wound that when one side of any particular
coil or circuit is under an inducing pole of one phase, its other side occupies a
position between two contiguous inducing poles of opposite sign of a different
phase, substantially as described.
Dated this 1st day of March 1898
FELL & JAMES,
Agents for the Applicant.