Improvements in Single Phase and Multiphase Alternate Current Motors.
Year: 1898

page_text: Date of Application, 11th Jan., 1898
1000
PROVISIONAL SPECIFICATION.
Improvements in Single Phase and Multiphase Alternate Current
Motors.
I, LLEWELYN BIRCHALL ATKINSON, of Western Mail Buildings, Saint Mary Street,
Cardiff, in the County of Glamorgan Civil Engineer, do hereby declare the nature
of this invention to be as follows:-
This invention relates to improvements in single phase alternate current motors
and has for its object the construction of a motor having a good starting power
with moderate starting current capable of being regulated as to speed and a
further part of my invention consists in means whereby a high power factor may
be attained.
My invention is more particularly applicable to certain classes of induction
motors and is as to part an extension of certain improvements for which Letters
Patent No. 15174/1895 have already been granted to me.
In the above mentioned patent means are described for starting a single phase
induction motor by having brushes pressing on the collector of the armature and
closed on themselves so as to short circuit the armature relatively to the inducing
axis only whilst to provide a magnetic field in which the armature may revolve
coils are provided connected in series with the inducing winding.
My further improvement consists in connecting the brushes and so short circuit-
ing the armature through these coils so that the magnetic field is produced by
and in phase with the armature current instead of the primary current.
further part of my invention relates to the prevention of sparking at the brushes
which is effected as follows:
A
The sparking at the brushes of alternating current motors with commutators
arises for the most part from the fact that the brushes short circuit armature
coils through which an alternating flux is passing. In the motor as constructed
according to my invention the short circuited coil is rotating in a magnetic field
(the inducing field) and by proportioning this magnetic field so that it has a proper
strength relative to the speed and to the strength of the motor field which is sett-
ing up induced currents in the short circuited coil the E.M. forces due to induction
and to rotation may be balanced when no sparking results the respective inducing
and motor field being in proper phase to effect this result. Where the motor
has to start constantly under load and it is desirable to use brushes of copper or
of low resistance there is a weakening of the motor field, due to the current in the
coil short circuited under the brush and this I largely avoid by the following
construction. The armature is wound with two circuits connected to alternate
collector sections. There are two sets of brushes at each point of collection
insulated from one another. These are connected each to the brush of opposite
pressure belonging to the same circuit on the armature. either directly or through
one of the magnet exciting coils described. By making the brushes of not greater
width than the width of a section on the collector the coils on the armature are
not directly short circuited by the brushes but only through intermediate sections

page_text: or coils depending on how far apart on the collector these separate bushes are
set and hence the induced currents are rendered comparatively small and their
detrimental effect obviated. The brushes may be made with carbon or high
resistence points which do short circuit but the principle remains the same.
A motor constructed according to the foregoing description, will start with the
full load on and gives the same tuming moment per ampere supplied at start-
ing, as when running, but a further part of my improvement relates to reducing
the current at starting or reducing the speed by the use of an auto-transformer, or
a regulating transformer, or by embodying the latter in the construction of the
motor itself. This I carry out as follows, When the motor is running at the
normal speed there is a current supplied at the line pressure; when the motor is
not running, or running slowly, a much smaller line pressure will give the same
current.
To
By use of an auto-transformer or regulating transformer between the line and
the motor, the pressure on the motor may be reduced using the full line pressure,
and the same armature current will be produced with a smaller line current.
regulate the speed, the same method may be adopted, by regulating the pressure
in the motor to give the armature current required at the pressure required. In
place of using an external regulating transformer or auto-transformer the same
result may be obtained by winding the inducing winding with a symmetrical two
path closed winding, wand by varying the point of connection of the supply circuit,
so that the inducing axis may be moved relatively to the axis of the short circuit
ing brushes. By this means the resultant E.M.F. in the armature windings may
have any value between zero and the full value with the same results as before
described.
A further part of my invention relates to a method of improving the power
factor of the motor. The principle on which this is based is as follows:-
The E.M.F. of supply and the current supplied are not in phase, because there
is always an idle or magnetising current, one fourth of a period behind the true
working current.
If the phase of the induced current in the armature can be made to lead on
the phase of the induced E.M.F. the inducing current may be made to coincide
in phase with the applied E.M.F. the induced current then furnishing the idle or
magnetising component. This result may be produced as is known by con-
densers, but I produce it by supplying a magnetic field in which the armature
rotates, and having no inductive effect on the armature; the said field (which may
be termed a compensating field) being in phase one fourth of a period behind the
phase of the supply E.M.F. As this field also involves the supply of an idle current
it is necessary to speed the motor in manner as follows:
In an induction motor with a motor field of the same magnitude as the inducing
field, when the speed of the motor is such that a point in the armature passes one
pair of poles in the periodic time the motor is said to be running at the synchronous
speed. In the motor constructed according to my invention if the inducing
field, the motor field, and the compensating field are all of the same magnitude, the
motor must run at three times the synchronous speed, when the power factor will
be unity with other proportions, other speeds must be used.
Although the methods described of starting and working the motors are those to
which this invention especially relates. it will be understood that the methods
may relate to starting only, and that when started the motor may have all its
armature coils short circuited and the brushes removed, or the brush circuit
opened, or have its coils short circuited in groups through slip rings or otherwise
when the motor will run as an ordinary monophase motor in manner well under-
stood or it may have an independent winding on the armature as on an ordinary
synchronous generator or motor, adopted for connection to the source of supply,
and the winding on the armature with brushes may be connected to the magnet-
ising coils which will then be excited by a continuous current, and the motor
will run as a synchronous motor; or without an independent winding by use of

page_text: slip rings, connected to opposite points on the armature the motor may be made
to run as a synchronous motor, acting as a rotary converter to magnetise the field
magnets with a continuous current.
It will be understood that although for the most part the foregoing description
applies to motors having single pairs of poles the description caeteris paribus will
apply to motors having multiple pairs of poles.
In order to reduce as far as possible the magnetic leakage between the inducing
and induced circuits, the inducing and induced circuits must be made as far as
Fossible to be geometrically coincident, and this I effect as follows:
Where the winding of the armature is of the ordinary type which may be termed
diametral, the induced circuit forms a regularly distributed sheet of currents over
the whole pole face, and the inducing winding must be either of the same type
as the armature winding that is a two-path distributed winding or of the class
described and claimed in my Specification of British Letters Patent No. 15174/1895
and there termed a spiral non crossing distributed winding..
Where it is preferred to make the inducing winding of a type where the coils
on each axis are contained in one or two holes surrounding the pole face, I make
the winding of the armature a chord winding and this gives a current distribution
on the armature corresponding to that on the inducing system.
Although I prefer to regulate the speed of the motor by varying the terminal
pressure as described or by varying the effective induced E.M.F. of the armature
in manner described, as by these means, the power factor is best maintained, and
the speed may be regulated by varying the strength of the motor field by increas-
ing or diminishing the number of turns of the magnetising coils, or by shunting
the same, or by rocking the brushes from the vertical axis so as to allow the current
in the armature coils to add to or diminish the effective ampere turns motor field
axis.
Improvements in Single Phase and Multiphase Alternate Current
Motors.
I, LLEWELYN BIRCHALL ATKINSON, of Western Mail Buildings, St. Mary Street,
Cardiff, in the County of Glamorgan, Civil Engineer, do hereby declare the nature
of this invention and in what manner the same is to be performed to be particu-
larly described and ascertained in and by the following statement:-
-
This invention relates to improvements in single phase alternate current motors,
and has for its object the construction of a motor having a good starting power
with moderate current capable of being regulated as to speed and
further part of my invention consists in means whereby a high power factor may
be attained.
a
My invention is more particularly applicable to certain classes of induction
motors, and is as to part an extension of certain improvements for which Letters
Patent No. 15174 of 1895 have already been granted to me.
In the above mentioned patent means are described for starting a single phase
induction motor, by having brushes, pressing on the collector of the armature, and
closed on themselves so as to short circuit the armature relatively to the inducing

page_text: axis only, whilst to provide a magnetic field in which the armature may revolve,
coils are provided connected in series with the inducing winding.
My further improvement consists, in connecting the brushes and so short circuit-
ing the armature through these coils, so that the magnetic field is produced by
and in phase with the armature current instead of the primary current. A
further part of my invention relates to the prevention of sparking at the brushes
which is effected as follows:-
The sparking at the brushes of alternating current motors with commutators
arises, for the most part, from the fact that the brushes short circuit armature
coils through which an alternating flux is passing. In the motor, as constructed
according to my invention, the short circuited coil is rotating in a magnetic field
(the inducing field), and by proportioning this magnetic field so that it has a proper
strength relative to the speed and to the strength of the motor field, which is set-
ting up induced currents in the short circuited coil, the E.M. forces, due to induction
and to rotation, may be balanced, when no sparking results, the respective inducing
and motor fields being in proper phase to effect this result. Where the motor
has to start constantly under load, and it is desirable to use brushes of copper or
of low resistance, there is a weakening of the motor field, due to the current in the
coil, short circuited under the brush, and this I largely avoid by the following
construction. The armature is wound with two circuits connected to alternate
collector sections. There are two sets of brushes at each point of collection,
insulated from one another. These are connected each to the brush of opposite
pressure, belonging to the same circuit on the armature, either directly or through
one of the magnet exciting coils described. By making the brushes of not greater
width than the width of a section on the collector, the coils on the armature are
not directly short circuited by the brushes, but only through intermediate sections
or coils, depending on how far apart on the collector these separate brushes are
set, and hence the induced currents are rendered comparatively small and their
detrimental effect obviated. The brushes may be made with carbon or high
resistance points, which do short circuit, but the principle remains the same."
A motor constructed according to the foregoing description, will start with the
full load on, and gives the same turning moment per ampere supplied at start-
ing, as when running, but a further part of my improvement relates to reducing
the current at starting or reducing the speed by the use of an auto-transformer, or
a regulating transformer, or by embodying the latter in the construction of the
motor itself. This I carry out as follows:-
-
When the motor is running at the normal speed there is a certain current_sup-
plied at the line pressure; when the motor is not running, or running slowly, a
much smaller line pressure will give the same current.
By use of an auto-transformer, or regulating transformer, between the line and
the motor, the pressure on the motor may be reduced using the full line pressure,
and the same armature current will be produced with a smaller line current. To
regulate the speed, the same method may be adopted, by regulating the pressure
in the motor to give the armature current required at the pressure required. In
place of using an external regulating transformer or auto-transformer, the same
result may be obtained by winding the inducing winding with a symmetrical two-
path closed winding, and by varying the point of connection of the supply circuit,
so that the inducing axis may be moved relatively to the axis of the short circuit,
ing brushes. By this means the resultant E.M.F. in the armature windings may
have any value between zero and the full value, with the same results as before
described.
A further part of my invention relates to a method of improving the power
factor of the motor. The principle on which this is based is as follows:-
The E.M.F. of supply, and the current supplied, are not in phase, because there
is always an idle or magnetising current, one fourth of a period behind the true
working current.
If the phase of the induced current in the armature can be made to lead on

page_text: the phase of the induced E.M.F. the inducing current may be made to coincide
in phase with the applied E.M.F. the induced current then furnishing the idle or
magnetising component. This result may be produced, as is known, by con-
densers, but I produce it by supplying a magnetic field in which the armature
rotates, and having no inductive effect on the armature, the said field (which may
be termed a compensating field) being in phase one fourth of a period behind the
phase of the supply E.M.F. As this field also involves the supply of an idle current
it is necessary to speed the motor in manner as follows:-
In an induction motor' with a motor field of the same magnitude as the inducing
field, when the speed of the motor is such that a point in the armature passes one
pair of poles in the periodic time, the motor is said to be running at the synchronous
speed. In the motor, constructed according to my invention, if the inducing
field is of the same magnitude as the motor field with the compensating field, the
motor must run at three times the synchronous speed, when the power factor will
he unity with other proportions, other speeds must be used.
Although the method described of starting and working the motors are those to
which this invention especially relates, it will be understood that the methods
may relate to starting only, and that when started the motor may have all its
armature coils short circuited, and the brushes removed; or the brush circuit
opened or have its coils short circuited in groups through slip rings or otherwise,
when the motor will run as an ordinary monophase motor in manner well under-
stood or it may have an independent winding on the armature as on an ordinary
synchronous generator or motor, adopted for connection to the source of supply,
and the winding on the armature with brushes may be connected to the magnet-
ising coils, which will then be excited by a continuous current, and the motor
will run as a synchronous motor: or without an independent winding by use of
slip rings, connected to opposite points on the armature, the motor may be made
to run as a synchronous motor, acting as a rotary converter to magnetise the field
magnets with a continuous current.
It will be understood that although, for the most part the foregoing description
applies to motors having single pairs of poles, the description cæteris paribus will
apply to motors having multiple pairs of poles.
In order to reduce as far as possible the magnetic leakage between the inducing
and induced circuits, the inducing and induced circuits must be made as far as
possible to be geometrically coincident, and this I effect as follows:-
Where the winding of the armature is of the ordinary type which may he termed
diametral, the induced circuit forms a regularly distributed sheet of currents over
the whole pole face, and the inducing winding must be either of the same fyne
as the armature winding, that is a two-nath distributed winding. or of the class
described and claimed in my Specification of British Letters Patent No. 15174
of 1895. and there termed a spiral non-crossing distributed winding.
Where it is preferred to make the inducing winding of a type where the coils
on each axis are contained in one or two holes surrounding the pole face. I make
the winding of the armature a chord winding. and this gives a current distribution
on the armature corresponding to that on the inducing system.
Although I prefer to regulate the speed of the motor by varving the terminal
pressure as described, or by varving the effective induced E.M.F. of the armature
in manner described, as by these means.-the power factor is best maintained, and
the speed may be regulated by varving the strength of the motor field. by increas-
ing or diminishing the number of turns of the magnetising coils, or by shunting
the same, or by rocking the brushes from the vertical axis so as to allow the current
in the armature coils to add to or diminish the effective ampere turns in the motor
feld axis.
!
ד'
And in order that my invention may be the better understood. I now proceed to
describe the same in reference to the accompanying drawings and to the letters
and figures marked thereon. Like letters refer to like parts in the various figures.
Figure 1 shows in diagrammatic form the motor constructed according to my

page_text: present invention, where A A is the inducing axis and B B the axis of the motor
field. The armature winding is a continuous one of any of the usual types, and the
inducing winding is preferably a spiral non-crossing winding, as described in
Letters Patent No. 15174 of 1895.
On the axis of B B are the magnetising coils which may be wound to enclose
the whole area to be magnetised; that is this winding need not be a distributed one.
Figure 2 shews my improved method of connecting the brushes pressing on the
collector through the magnetizing windings on the axis B B, so that the armature
circuit is closed through them.
Figure 3, shews in diagram the armature wound with two separate circuits con-
nected to alternate collector sections, and divided brushes h h h¹ h¹ and separate
connecting circuits for preventing the short circuiting of the coils under the brush.
The brushes may be on adjacent sections of the collector as shewn in Figure 3,
or may be separated by one or more clear sections with the same object in view.
Figure 4, shews the arrangement for connecting the motor to an auto-trans-
former m for the purpose of diminishing the applied pressure and supply current,
by varying the point of application of the connections of the motor to those of the
auto-transformer.
Figure 5 shews the connection of the motor to a regulating transformer t. The
supply is connected to S, S, the primary of the transformer, the motor a, a, to the
secondary of the transformer. By varying the angular position of the secondary,
the pressure applied to a a is varied, thus regulating the speed and power of the
motor.
Figure 6 shews the construction of the motor with a continuous winding (a) on
the inducing system, so that by varying the position of attachment of the supply
connections, the inducing axis A A may be varied in position as A A and thus
the resultant E.M.F. on the armature winding be varied bb are the motor field
magnetizing coils.
Figure 7 shews in a distorted diagram the relative connections of coils forming
the compensating field C, C, the motor field B, B, and inducing field A, A, on the
motor for the purpose of controlling the phase of the armature current, and of the
inducing current relative to the supply E.M.F. The coils on C C are connected to
the supply main with those on A, A. The coils on B, B, are in series with the
armature as before. The fields C C, & B B, though shown here alongside one
another for diagrammatic identification actually in practice coincide & lie at right
angles to the field A, A.
Figure 8 shews the arrangement of the motor with slip rings V V V and
brushes f f f to short circuit the whole armature, to enable it to be worked as a
motophase motor, the circuit bb being opened by the switch r.
Figure 9 shews the arrangement of the motor with slip rings V, V, to which the
supply is led, running as a synchronous motor, with continuous winding acting as
rotary converter to supply continuous current to the magnetizing coils b₁ the
circuit a a¹ being disconnected.
Figure 10 shews the arrangement of chord winding on the armature and
Fig. 11 shews one coil of the inducing winding developed, these arrangements being
for the purpose of reducing the magnetic leakage as described.
Having now particularly described and ascertained the nature of this
invention and in what manner the same is to be performed I declare that what
I claim is:
1st. A single phase alternate current motor, having in combination, an inducing
system, an armature with commutator, short circuited relative to the axis of this
system by brushes, a motor field excited by coils in series with the armature and
brushes, substantially as described and illustrated in Figures 1 and 2.
2nd. A single phase alternate current motor as claimed in Claim 1 in which the
induced E.M.F., in the coil, short circuited under the brush, is balanced by the
E.M.F. due to rotation in the inducing field, substantially as described.
لمان سالامات

page_text: 3rd. A single phase alternate current motor, as claimed in Claims 1 and 2,
having a double winding on the armature, in combination with two series of
brushes separately and independently connected or short circuited, so as to avoid
short circuiting of the armature coil and the brush, substantially as described and
illustrated in Figure 3.
4th. In alternate current motors as claimed in Claims 1 and 2, in combination
with inducing and motor fields, a compensating field, in which the armature rotates
for the purpose of controlling the phase of the armature current, so as to increase
the power factor, substantially as described and illustrated in Figure 7.
5th. The combination with a motor as described of an auto-transformer or regu-
lating transformer, for the purpose of regulating the speed and power without use
of resistances, substantially as described and illustrated in Figures 4 and 5.
6th. A motor, as claimed in Claims 1 and 2, having an inducing winding of the
closed type so arranged as to enable the point of supply to be varied, for the pur-
pose of varying the induced E.M.F. in the armature, substantially as described
and illustrated in Figure 6.
7th. In a motor as claimed in Claims 1 and 2 the combination with the armature
as described, of slip rings and brushes, adapted to short circuit the armature, with
means for disconnecting the magnetizing circuit, so as to allow the motor to run
as a monophase motor, as described and illustrated in Figure 8.
8th. In a motor as described, the combination with the armature winding as
described, of a separate polar winding on the armature, adapted to be connected
to the source of supply, and means for utilizing the starting winding, as a generat-
ing winding for continuous currents, magnetizing the motor and forming a
synchronous motor, substantially as described.
9th. In a motor as described, the combination with the armature winding as
described, of slip rings connected to points on the winding, adapted to be con-
nected to the source of supply, and acting as a synchronous motor, also as a
rotary converter to magnetize the machine with the continuous current, substan-
tially as described and illustrated in Figure 9.
10th. In a motor as claimed in Claims 1 and 2, the combination of a distributed
winding on the inducing circuit with a distributed closed winding on the induced
or armature circuit, and with a distributive or isolated magnetizing winding, as
described and illustrated in Figure 1.
11th. In a motor as claimed in Claims 1 and 2 the combination of a partially
distributed winding on the inducing circuit, with a closed chord winding on the
induced or armature circuit, as described and illustrated in Figures 10 and 11.
12th. The construction of multipolar motors embodying the parts and functions
claimed in Claims 1 to 11.
FELL & JAMES,
1, Queen Victoria Street, London, E.C., Agents for the Applicant.