Improvements in Alternate Current Motors.
Year: 1888

page_text: Date of Application, 18th Dec., 1888
Complete Specification Left, 14th Sept., 1889-Accepted. 26th Oct.. 1889
PROVISIONAL SPECIFICATION.
Improvements in Alternate Current Motors.
I, ERNEST WILSON, of 2 Rose Mount, Church Lane, Charlton, S.E., in the
County of Kent, Electrical Engineer, do hereby declare the nature of this invention
to be as follows:-
When two alternate currents of the same intensity having a difference in phase
of 90° are suitably superposed at right angles to one another they produce a revolving
field of magnetism capable of acting as a revolving permanent magnet.
There are several arrangements by which two alternate currents as above
described can be made to produce a revolving field of magnetism, as may be under-
stood on reference to the accompanying diagrams in all of which P P represent
the terminals for one of the currents and S S the terminals for the other.
(a) Figure 1 represents a known arrangement of two circuits one for each
current at right angles to one another; multiple sets of such circuits might be
employed.
(6) Figure 2 also represents a known arrangement of four coils or bobbins, a
pair for each current.
(c) Figure 3 represents a novel arrangement of two complete circuits wound on
one another, one circuit for each current.
(d) Figure 4 also represents a new arrangement in which one complete circuit
takes both currents.
In constructing an electric motor I apply any of these arrangements or combina-
tions of them to produce two concentric revolving fields of magnetism. The one
field I term the "Armature Field " because it is induced by the two alternate
currents passing round the armature (or moveable) coils of the motor. The other I
term simply the "Field " because it is induced by the same two alternate currents
passing round the field (or stationary) coils of the motor.
Both these fields have the same angular velocity and they may or may not he of
the same strength. If they coincided in polarity there would be no force tending to
cause rotation, but if one of them is made to lag, say a few degrees, behind the
other, there is a tendency for the armature to rotate.
I may take for example case (d) shewn in Figure 4, and arrange the two fields for
a motor such as is indicated diagrammatically by Figure 5. The inner circuit
represents the armature coils and the onter circuit represents the field coils. The
armature and commutator may be of the ordinary type used in continuous current
machines with four brushes applied to the commutator in correspondence with the
points P.P. S.S. respectively. Under these conditions the two fields would revolve
with their poles diametrically coinciding, and no rotation would be produced. But if
the brushes are moved round into a position such as is shewn in Fig. 6, there will be
a magnetic attraction between the two fields, or the two fields will tend to coincide
with one another, and in so doing the armature will be caused to rotate in the
direction of pull.
The direction of rotation can be reversed by moving the brushes over to the other
side of the middle position of Figure 5, or by reversing the direction of one of the
alternate currents.
The two alternate currents employed can be made to have the required phase
difference by various well known methods. When this is done in the generator
itself, the motor may be operated at half the potential on the three wire system by
connecting the motor circuits in the proper order to three terminals making the
same lead common to both circuits.
The phase of the alternate currents may be modified in order to vary the angular
velocity of the two fields, and where a tendency to synchronism is desired,

page_text: coils closed on themselves could in addition to the above arrangement be wound on
the armature or field or on both.
In order that a motor such as I have described may work with a single alternate
current circuit, one of the alternate currents can be obtained from the other hy
induction. For this purpose there may be a duplicate set of coils on the armature
or on the field or on both, with suitable resistances so as to supply the second
alternate current as in a transformer, and this induced alternate current may be sent
round the armaturo and field coils respectively, thereby causing the two required
revolving fields of magnetism. According to another arrangement, I produce the
two revolving fields of magnetism by employing, besides the coils that are in
the circuit, additional coils closed on themselves, arranged in suitable positions on the
ring or on the armature or on both. These coils by the induction on them have the
effect of throwing back the positions which the poles would otherwise assume, but
when the induced currents in them subside, they permit the poles to advance in their
regular course.
More than two revolving fields of magnetism may be employed. For instance,
when the armature is of the Gramme Ring Type, there may be besides the outer
field coils, other field coils placed inside the armature with the connections such
that the alternate currents pass round the three sets of coils, those of the outer
field, those of the armature, and those of the inner field, giving three concentric
revolving fields of magnetism. The outer and inner revolving fields coinciding in
polarity would both tend to pull the armature round. A greater number of revolving
fields of magnetism could be thus combined.
When only two revolving fields of magnetism are employed, the motor may be
constructed in the following manner.
The field coils are wound either on an outer
ring or on pieces of this ring which project radially towards the armature, this ring
being made or built up preferably of wire or laminated iron. "The armature may be
of the Siemens Drum Type or of the Gramme Ring Type arranged to revolve
inside the ring and provided with a commutator as in ordinary continuous current
dynamo machines, having four brushes bearing at equal distances apart on the com-
mutator, and capable of being all shifted round on the commutator, still maintaining
their relative intervals.
In the case where I employ induced coils closed on themselves as above described,
to throw back the positions of the poles, only two opposite brushes are necessary.
The two alternate currents, circulating in the coils of the field or outer ring and
in the armature, produce as described, two revolving fields of magnetism. They
may be made to coincide diametrically or to have an angular lead either by shifting
the brushes on the commutator, or by shifting the outside ring relatively to the
brushes; and thus the armature may be made to remain at rest or to rotate in either
direction.
A motor thus arranged can work on an ordinary alternate current circuit. It is
self starting and can be stopped almost immediately without breaking circuit by
making the two fields coincide in their polarity, and it can be worked in either
direction according as the brushes are moved to the right or to the left of the
point where the two fields coincide in polarity..
Dated this 17th dex of De 1000
ABEL & IMRAY,
Agents for the Applicant.
COMPLETE
SPECIFICATION.
Improvements in Alternate Current Motors.
I, ERNEST WILSON of 2 Rose Mount, Church Lane, Charlton S.E. in the County
of Kent, Electrical Engineer, 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 :-
When two alternate currents of the same intensity having a difference in phase

page_text: of 90° are suitably superposed at right angles to one another they produce a revolving
field of magnetism capable of acting as a revolving permanent magnet.
There are several arrangements by which two alternate currents as above described
can be made to produce a revolving field of magnetism, as may be understood on
reference to the diagrams Figs. 1 to 6 inclusive accompanying my Provisional
Specification, and the six additional figures 7 to 12 inclusive filed herewith.
In the diagrams Figs. 1 to 6 PP represent the terminals for one of the currents and
SS the terminals for the other.
(a) Fig. 1 represents a known arrangement of two circuits one for each current
at right angles to one another; multiple sets of such circuits might be employed.
(b) Fig. 2 also represents a known arrangement of four coils or bobbins, a pair
for each current.
(c) Fig. 3 represents a novel arrangement of two complete circuits wound on one
another, one circuit for each current.
(d) Fig. 4 also represents a new arrangement in which one complete circuit takes
both currents.
In constructing an electric motor I apply any of these arrangements or combina-
tions of them to produce two concentric revolving fields of magnetism. The one
field I term the "Armature Field," because it is induced by the two alternate currents
passing round the armature (or moveable) coils of the motor. The other I term
simply the "Field " because it is induced by the same two alternate currents
passing round the field (or stationary) coils of the motor.
Both these fields have the same angular velocity and they may or may not be of the
same strength. If they coincide in polarity there would he no force tending to
cause rotation, but if one of them is made to lag, say a few degrees behind the
other, there is a tendency for the armature to rotate. I may take for example
case (d) shewn in Fig. 4, and arrange the two fields for a motor such as is indicated
diagrammatically by Fig. 5. The inner circuit represents the armature coils and
the outer circuit represents the field coils. The armature and commutator may be
of the ordinary type used in continuous current machines with four brushes, applied
to the commutator in correspondence with the points PP. SS respectively. Under
these conditions the two fields would revolve with their poles diametrically coinciding,
and no rotation would be produced. But if the brushes are moved round into a
position such as is shewn in Fig. 6, there will be a magnetic attraction between the
two fields, or the two fields will tend to coincide with one another, and in so doing
the armature will be caused to rotate in the direction of pull.
The direction of rotation can be reversed by. moving the brushes over to the other
side of the middle position of Fig. 5, or by reversing the direction of one of the
alternate currents.
The two alternate currents employed can be made to have the required phase
difference by various well known methods. When this is done in the generator itself,
the motor may be operated at half the potential on the three wire system by
connecting the motor circuits in the proper order to three terminals making the same
lead common to both circuits.
The phase of the alternate currents may be modified in order to vary the angular
velocity of the two fields, and where a tendency to synchronism is desired, coils
closed on themselves could in addition to the above arrangement be wound on the
armature or field or on both.
'
In order that a motor such as I have described may work with a single alternate
current circuit, one of the alternate currents can be obtained from the other by
induction.
For this purpose there may be a duplicate set of coils on the armature or on the
field or on both with suitable resistances so as to supply the second alternate current
as in a transformer, and this induced alternate current may be sent round the
armature and field coils respectively, thereby causing the two required revolving
fields of magnetism. According to another arrangement produce the two
revolving fields of magnetism by employing besides the coils that are in the circuit

page_text: additional coils closed in themselves, arranged in suitable positions on the ring or
on the armature or on both. These coils by the induction on them. have the effect
of throwing back the positions which the poles would otherwise assume, but when
the induced currents in them subside they permit the poles to advance in their
regular course.
-
More than two revolving fields of magnetism may be employed. For instance,
when the armature is of the Gramme Ring Type, there may be besides the outer
field coils, other field coils placed inside the armature with the connections such that
the alternate currents pass round the three sets of coils, those of the outer field,
those of the armature, and those of the inner field, giving three concentric revolving
fields of magnetism. The outer and inner revolving fields coinciding in
polarity would both tend to pull the armature round. A greater number
of revolving fields of magnetism could be thus combined. When only two
revolving fields of magnetism are employed, the motor may be constructed in the
following manner. The field coils are wound either on an outer ring or on
pieces of this ring which project radially towards the armature, this ring being made
or built up preferably of iron wire or laminated iron. The armature may be of the
Siemens Drum Type or of the Gramme Ring Type arranged to revolve inside the
ring and provided with a commutator as in ordinary continuous current dynamo
machines, having four brushes bearing at equal distances apart on the commutator,
and capable of being all shifted round on the commutator, still maintaining their
relative intervals.
In the case where I employ induced coils closed on themselves as above
described, to throw back the positions of the poles, only two opposite brushes are
necessary.
The two alternate currents, circulating in the coils of the field or outer ring and in
the armaturo, produce as described two revolving fields of magnetism. They may be
made to coincide diametrically or to have an angular lead either by shifting the
brushes on the commutator, or by shifting the outside ring relatively to the
brushes; and thus the armature may be made to remain at rest or to rotate in either
direction.
A motor thus arranged can work on an ordinary alternate current circuit. It is
self starting and can be stopped also immediately without breaking circuit by making
the two fields coincide in their polarity, and it can be worked in either direction
according as the brushes are moved to the right or to the left of the point where the
two fields coincide in polarity.
Fig. 7 is a side view and Figs. 8 and 9 are respectively front and back views of a
motor wound as in the case (c) above referred to. Each of the electro magret
bobbins B is wound on a projecting core D with two independent circuits, repre-
sented diagrammatically in Figs. 10, 11 and 12. The armature is also wound with
two circuits the commutators C₁ and C₂ are connected to them respectively as in the
ordinary Siemens Drum Armature. The two segments S₁ and S, carry the brush
holders as in ordinary machines, these segments having circular slots for the purpose
of adjusting the relative distance between the brushes.
Although only 4 bobbins B are shewn, there may be any greater number.
When the motor is to be worked on two alternate current circuits as bereinbefore
described the coils are connected as indicated in Fig. 10. A₁ and A.. indicate the
two alternators supplying currents which differ in phase by. a quarter period. In
this case the brushes on the commutators C₁ C, are adjusted so that those of the one
circuit are at right angles to those of the other.
When the motor is to be worked on an alternate current circuit as bereinbefore
described, the coils are connected as indicated by Figs. 11 and 12. The brushes are
in this case moved towards one another until they occupy the most effective position.
The external resistances R₁ R, and R, are determined by experiment. In Fig. 11
and 12 the circuit or circuits in connection with the alternator A may be termed the
Primary." The other circuit which is not in connection with the alternator may be
termed the "Secondary" because the currents are induced in it as in a transformer.
$6

page_text: Having now particularly described and ascertained the nature of this inven
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. An alternate current electric motor the movement of which is produced as
herein described by two concentric magnetic fields that are caused to revolve by the
excitation due to superposed currents of different phase.
2. In an alternate current motor such as is above referred to, winding the field and
armature coils each with one complete circuit having a pair of terminals at right
angles to another pair, or either or both sets of coils with two complete circuits
having the terminals of the one at right angles to those of the other.
3. In an alternate current motor such as is above referred to in substitution for one
of the primary circuits connected to the leads, a circuit closed upon itself and
arranged so as to have secondary alternating currents induced in it from the
primary.
Dated this 13th day of September 1889.
ABEL & IMRAY,
Agents for the Applicant.