Improvements in or relating to Electric Motors.
Year: 1889

page_text: Date of Application, 23rd Feb., 1889
Date of Application, 23rd Feb., 1889
000
1000
PROVISIONAL SPECIFICATION.
Improvements in or relating to Electric Motors.
A communication from abroad by THE WESTINGHOUSE ELECTRIC COMPANY, of
Pittsburgh, Pennsylvania, United States of America.
I WILLIAM PHILLIPS THOMPSON F.C.S. M.I.M.E. of the Agency for Foreign
Patent Solicitors, 6, Lord Street, Liverpool, and 6 Bank Street, Manchester both in
the County of Lancaster, and 323 High Holborn, in the County of Middlesex Civil
Engineer, do hereby declare the nature of this invention to be as follows:-
The invention relates to the class of electric motors designed to be operated by
alternating electric currents, and the object is to provide a motor which will readily
start from a state of rest and gradually increase its speed until it reaches a maximum,
dependent upon the number of alternations per minute in the electric current.
In carrying out the invention the field-magnet, is caused to be excited by currents
transmitted through a suitable commutator and may conveniently be divided into two
different circuits which respectively include the coils applied to the alternate poles of
the field-magnet. The magnetization of the field-magnet is carried to a very high
point of saturation at the commencement and gradually decreased as the motor
gradually increases its speed.
To accomplish this a converter is employed for delivering secondary or induced
currents to the field-magnet circuit, and the effect of this converter may be varied so
as to apply a higher or lower electromotive force to the field as may be required. Two
converters may be used, one of which maintains a suitable potential for the field-
magnets when the motor has reached a proper speed, the other being so connected as
to add its effect to the first before that speed is reached. The adjustment of the
electromotive force of the second converter may be effected in various ways, and
among others by varying the difference of potential on its primary coil by means of a
resistance in shunt thereto. The latter resistance may be also connected in series with
the armature, and when so connected, its gradual reduction increases the armature
current, and at the same time decreases the difference of potential on the field
until it is reduced to that of the first converter.
In the accompanying drawing there is shown in Figure 1. a general organization.
of circuits and apparatus for carrying out one portion of the invention.
Referring to this Figure, A' represents a suitable source of alternating electric.
currents. Conductors and L² are led from the respective poles of this generator.
In the conductor a leading from the conductor L₁ to the conductor L2, there is
included the primary coil pl of a converter C. The secondary coil s¹ of this con-
verter is connected at one terminal with a conductor a² leading to the field-magnet
coils of the motor. The conductor a² divides at a point a³ into branches at and a³.
The branch a leads through the coils e¹, e³, e5 and e7, which alternate in position with
the coils e2, et, eo, and es. These are applied to the alternate poles f of the field-
magnet E of the motor. The coils e², e, etcetera, are included in the branch conductor a³.
The conductor at leading from the field-magnet is connected with a brush h¹
applied to a circuit-changing commutator H¹ upon the shaft of the armature K of the
motor. The conductor a, leading from the field-magnet, is connected with a corre-
sponding brush h² applied to the commutator. A brush k applied to the commutator H
makes alternate contact with the plates against which the brushes h¹ and h²
respectively.rest. This brush is connected by a conductor a through the secondary
coil 82 of a converter 02, thence back to the remaining terminal of the secondary coil s¹
of the converter C¹. It will be seen thus that the secondary circuits of the con-
verters C and C² are completed alternately through the conductors at and a³, thus
causing the poles of the field-magnet to be alternately vitalized.

page_text: The primary circuit of the converter C2 is connected in a shunt upon a resistance R
included in a conductor 62 leading from the line L2 to a contact brush n², applied to
the contact ring m² upon the armature of the motor. A second ring m¹ upon this shaft
is provided with a second brush n¹ which is connected by a line 6¹ with the line L.
The rings m¹ and m² are respectively connected with the terminals 1 and 2 of the
armature coils. More or less of the resistance R may be included between the
terminals of the primary coils p² of the converter C, by means of a lever 1 or in any
other convenient manner.
When the machine is to be started, the resistance R is included in shunt upon the
converter C², so that the maximum difference of potential is applied to the coil p².
The current induced in the secondary coil 82 is added to the current which is being
induced at the same time in the secondary coil s¹ of the converter C₁ and the
combined currents serve to raise the field-magnet E to a point of high saturation.
The armature is meanwhile supplied with currents through the conductors b¹ and b².
As the rotation of the armature increases in rapidity the resistance may be gradually
cut out and this will cause the difference of potential at the terminals of the primary
coil p² to be diminished, and consequently the effect of the coil will be diminished
until finally, when the resistance R has been completely short-circuited, the converter
has no further effect. The converter C¹ then operates alone at a proper electromotive
force to maintain the field at its proper value. The speed of the armature has mean-
while been increasing until it has reached synchronism with the alternations of current
upon the circuit, and consequently the successive currents through the alternate field-
magnet coils will be in the same direction, and the motor is then working under proper
conditions.
In carrying out the second application of the invention, it is designed to apply in-
dependent electromotive forces to the armature and the field-magnet coils, and to
control the potentials as may be required during the increasing speed of the armature
in a somewhat different way. Electric currents are supplied to the armature through
a converter reducing the potential of the current upon the main line, in case it is too
great to be handled conveniently. Such a converter serves also to vary the potential
applied to the armature in a manner similar to that which would be accomplished by
the use of a rheostat. A second converter supplies the current to the field-magnet
coils, and this is so proportioned that the lowest potential it can yield is suitable
for the operation of the motor, after it has attained a proper speed and the flow
of current has become continuous in direction by reason of a commutating device
carried upon the shaft of the armature.
This portion of the invention will be described more in detail in connection
with Figure 2 of the drawings.
Referring to this Figure, A¹ represents a suitable source of alternating, pulsatory
or intermittent electric currents. L1 and L2 represent conductors leading from the
respective poles thereof. The primary coil of a converter C¹, of any suitable character,
is connected by conductors 1 and 2 between the conductors L1 and L2. The secondary
coil of this converter is connected at one terminal with a conductor 4, leading through
the current rectifying device H to the field-magnet coils e¹, e², etcetera, of the motor.
A conductor 3 also leading to the device H, may be placed in connection with
different points in the length of the secondary coil of the converter C', by means of a
switch S. This switch may be placed in contact with switch points t¹, t², t³, 14,
connected with different points of the length of the secondary coil.
The brushes 1 and 2 with which the conductors 4 and 3 are connected, are con-
tinually in contact with the conducting plates h¹, h2, of the device H. Two brushes ³
and which are respectively connected with the terminals of the field-magnet
coils, make contact with these plates alternately. When therefore, the armature is
revolving in synchronism with the reversals in the currents supplied thereto, the
current delivered to the field-magnet coils e', e², e³, e, will be continuous in direction.
The currents for the armature K of the motor are supplied through a second
converter C2. The primary coil of this converter is connected between the cou-
ductors Land L2, by conductors 5 and 6. The secondary coil of the converter, whose

page_text: active length is adjustable by means of a switch S' applied to points u¹, u², u³, has its
respective terminals connected with brushes n¹ and n² resting upon contact rings m¹
and m². These rings are respectively connected with the terminals of the armature coils.
Alternating currents will therefore be continuously supplied to the armature coils.
Currents having potentials independent of each other are thus supplied to the
armature and field-magnet coils, and these are independently controllable. The con-
verter C² is introduced for the purpose of reducing the potential of the current upon
the supply circuit in case that it is too high to be handled conveniently and also to
vary the potential of the current upon the armature in the same manner as would be
accomplished by the use of a rheostat. This exception, however, should be noticed;
by means of the converter, approximately the saine difference of potential will be
supplied to the armature even under considerable variation of current as the armature
acquires speed, whereas in the case of a rheostat, it is evident that as the current
increases the difference of potential would be decreased by reason of the greater
difference of potential included in the rheostat itself.
The converter C¹, through which current is supplied to the field-magnet is so pro-
portioned that the lowest electromotive force which it can produce will be suitable for
operation after the armature has attained a proper speed and the field-magnet current
becomes continuous in direction. It should be noted that the current in the field is
alternating as well as that in the armature, at all speeds except that of synchronism,
the commutator acting simply to reverse the relative directions of the two currents at
a given instant, until the speed is attained.
It is evident that the relative positions of the arinature and field may be reversed,
so that the armature remains stationary and is traversed by the alternating current,
while the field revolves and is supplied by a commutated current or periodically
changed alternating current as described. Such transposition is well known and has
been frequently employed.
Dated this 22nd day of February 1889.
COMPLETE SPECIFICATION.
Improvements in or relating to Electric Motors.
A communication from abroad by THE WESTINGHOUSE ELECTRIC COMPANY, of
Pittsburgh, Pennsylvania, United States of America.
I, WILLIAM PHILLIPS THOMPSON F.C.S. M.I.M.E. of the Agency for Foreign
Patent Solicitors 6, Lord Street, Liverpool and 6, Bank Street, Manchester both in
the County of Lancaster and 323 High Holborn in the County of Middlesex Civil
Engineer do hereby declare the nature of this invention and in what manner the
same is to be perforined, to be particularly described and ascertained in and by the
following statement:--
The invention relates to the class of electric motors designed to be operated by
alternating electric currents, and the object is to provide a motor which will readily
start from a state of rest and gradually increase its speed until it reaches a maximum,
dependent upon the number of alternations per minute in the electric current.
In carrying out the invention the field-magnet is caused to be excited by currents
transmitted through a suitable commutator and may conveniently be divided into two
different circuits which respectively include the coils applied to the alternate poles of
the field-magnet. The magnetization of the field-magnet is carried to a very high
point of saturation at the commencement and gradually decreased as the motor
gradually increases its speed.
To accomplish this, a converter is employed for delivering secondary or induced
currents to the field-magnet circuit, and the effect of this converter may be varied so
as to apply a higher or lower electromotive force to the field as may be required.
Two converters may be used, one of which maintains a suitable potential for the
field-magnets when the motor has reached a proper speed, the other being so con-

page_text: nected as to add its effect to the first before that speed is reached.
The adjustment
of the electromotive force of the second converter may be effected in various ways,
and among others by varying the difference of potential on its primary coil by means
of a resistance in shunt thereto. The latter resistance may be also connected in series
with the armature, and when so connected, its gradual reduction increases the armature
current, and at the same time decreases the difference of potential on the field until it
is reduced to that of the first converter.
In the drawing filed with the Provisional Specification, there is shown, in Figure 1,
a general organisation of circuits and apparatus for carrying out one portion of the
.invention.
The
Referring to this Figure, A' represents a suitable source of alternating electric
currents. Conductors 1 and L2 are led from the respective poles of this generator.
In the conductor a¹, leading from the conductor L₁ to the conductor L2, there is
included the primary coil p₁ of a converter C. The secondary coil s¹ of this converter
is connected at one terminal with a conductor a² leading to the field-magnet coils of
the motor. The conductor a² divides at a point a into branches a¹ and a³. The
branch a leads through the coils e¹, e³, e and e7, which alternate in position with the
coils e, e, e and es. These are applied to the alternate poles f of the field-magnet E of
the motor. The coils e², et, etcetera, are included in the branch conductor e.
conductor a leading from the field-magnet is connected with a brush h¹ applied to a
circuit-changing commutator H¹ upon the shaft of the armature K of the motor.
The conductor a, leading from the field-magnet is connected with a corresponding
brush h² applied to the commutator. A brush k applied to the commutator H makes
alternate contact with the plates against which the brushes h¹ and h² respectively rest.
This brush is connected by a conductor a through the secondary coil 82 of a con-
verter C², thence back to the remaining terminal of the secondary coil st of the con-
verter C¹. It will be seen thus that the secondary circuits of the converters C¹ and C²
are completed alternately through the conductors at and a³, thus causing the poles of
the field-magnet to be alternately vitalized.
The primary circuit of the converter C² is connected in a shunt upon a resistance R
included in a conductor 62 leading from the line L2 to a contact brush n²,
applied to the contact ring m² upon the armature of the motor. A second ring m¹
upon this shaft is provided with a second brush n¹ which is connected by a line 6¹
with the line L¹. The rings m¹ and m² are respectively connected with the terminals 1
and 2 of..the armature coils. More or less of the resistance R may be included
between the terminals of the primary coils p² of the converter C², by means of a
leyer or in any other convenient manner.
When the machine is to be started, the resistance R is included in shunt upon the
converter C², so that the maximum difference of potential is applied to the coil p².
The current induced in the secondary coil s² is added to the current which is being
induced at the same time in the secondary coil s¹ of the converter C, and the combined
currents serve to raise the field-magnet E to a point of high saturation. The
armature is meanwhile supplied with currents through the conductors 1 and 62. As the
rotation of the armature increases in rapidity, the resistance may be gradually cut out
and this will cause the difference of potential at the terminals of the primary coil p²
to be diminished, and consequently the effect, of the coil will be diminished until
finally, when the resistance R has been completely short-circuited, the converter has
no further effect. The converter C¹ then operates alone at a proper electromotive
force to maintain the field at its proper value. The speed of the armature has mean-
while been increasing until it has reached synchronism with the alternations of
current upon the circuit, and consequently the successive currents through the
alternate field-maguet coils will be in the same direction, and the motor is then
working under proper conditions.
In carrying out the second application of the invention, it is designed to apply
independent electromotive forces to the armature and the field-magnet coils, and
to control the potentials as may be required during the increasing speed of the
armature in a somewhat different way. Electric currents are supplied to the

page_text: armature through a converter reducing the potential of the current upon the main
line, in case it is too great to be handled conveniently. Such a converter serves
also to vary the potential applied to the armature in a manner similar to that
which would be accomplished by the use of a rheostat. A second converter
supplies the current to the field-magnet coils, and this is so proportioned that the
lowest potential it can yield is suitable for the operation of the motor, after it has
attained a proper speed and the flow of current has become continuous in direction
by reason of a commutating device carried upon the shaft of the armature.
This portion of the invention will be described more in detail in connection
with Figure 2 of the drawings.
Referring to this Figure, A' represents a suitable source of alternating, pulsatory
or intermittent electric currents. L1 and L2 represent conductors leading from the
respective poles thereof. The primary coil of a converter C¹, of any suitable
character, is connected by conductors 1 and 2 between the conductors I and I².
The secondary coil of this converter is connected at one terminal with a conductor 4,
leading through the current rectifying device H to the field-magnet coils e¹, e²,
etcetera, of the motor. A conductor 3 also leading to the device H, may be placed
in connection with different points in the length of the secondary coil of the con-
verter C¹, by means of a switch S¹. This switch may be placed in contact with
switch-points t¹, t², t³, t¹, connected with different points of the length of the
secondary coil.
The brushes and 2 with which the conductors 4 and 3 are connected, are
continually in contact with the conducting plates h¹, h², of the device H. Two
brushes 3 and 4 which are respectively connected with the terminals of the field-
magnet coils, make contact with these plates alternately. When therefore, the
armature is revolving in synchronism with the reversals in the currents supplied
'thereto, the current delivered to the field-magnet coils e¹, e², e³, et, will be continuous
in direction.
The currents for the armature K of the motor are supplied through a second
converter C². The primary coil of this converter is connected between the con-
ductors Land L', by conductors 5 and 6. The secondary coil of the con-
verter, whose active length is adjustable by means of a switch S2 applied to
points u¹, u², u³, has its respective terminals connected with brushes n¹ and n² resting
upon contact rings m¹ and m². These rings are respectively connected with the
terminals of the armature coils. Alternating currents will therefore be continuously
supplied to the armature coils.
Currents having potentials independent of each other are thus supplied to the
armature and field-magnet coils, and these are independently controllable. The
converter C2 is introduced for the purpose of reducing the potential of the
current upon the supply circuit in case that it is too high to be handled conveniently
and also to vary the potential of the current upon the armature in the same
manner as would be accomplished by the use of a rheostat. This exception, how-
ever, should be noticed; by means of the converter, approximately the same difference
of potential will be supplied to the armature even under considerable variation of
current as the armature acquires speed, whereas in the case of a rheostat, it is
evident that as the current increases the difference of potential would be decreased
by reason of the greater difference of potential included in the rheostat itself.
The converter C¹, through which current is supplied to the field-magnet, is so
proportioned that the lowest electromotive force which it can produce will be suitable
for operation after the armature has attained a proper speed. and the field-magnet
current becomes continuous in direction. It should be noted that the current in
the field is alternating as well as that in the armature, at all speeds except that
of synchronism, the commutator acting simply to reverse the relative directions of
the two currents at a given instant, until the speed is attained.
It is evident that the relative positions of the armature and field may be reversed, so
that the armature remains stationary and is traversed by the alternating current, while
the field revolves and is supplied by a commutated current or periodically changed

page_text: alternating current as describe.l. Such transposition is well known and has been
frequently employed.
Having now particularly described and ascertained the nature of the said
invention, and in what manner the same is to be performed, as communicated
to me by my foreign correspondents, I declare that what I claim is :-
1. The combination with the field-magnet of an electric motor, and a source of
current therefor, of a converter having its primary coils supplied with alternating
electric currents and its secondary coil connected to assist the field-magnet current,
and means for supplying more or less current to the primary coil of the converter.
2. The combination with the field-magnet coils of an electric motor, of a converter
having its secondary circuit connected through said coils, a second converter assisting,
in effect, the first named converter, and connections through the armature of the
motor independent of the field-magnet connections.
3. The combination with the field-magnet coils of an electric motor, of a converter
having its secondary circuit connected through said coils, a second converter assisting, in
effect, the first named converter, connections through the armature of the motor inde-
pendent of the field-magnet connections, and means for cutting the primary coil
of the second converter out of circuit.
4. The combination with the field-magnet coils of an electric motor and the
armature applied thereto, of a converter supplying currents to the field-magnet
coils, a circuit transforming commutator through which the secondary circuit of
said converter is completed, an artificial resistance included in the circuit of the
armature, means for including more or less of said resistance in circuit, and a
second converter having its primary coil connected in shunt upon said resistance
and its secondary coil in series with the secondary coil of the first named converter,
substantially as described.
5. The combination with the field-magnet of an electric motor having multiple
poles, of branch conductors including the coils applied to the alternate poles, a
commutator upon the armature-shaft of the motor, means for completing the
circuit-connections through said branch circuits alternately, and a source of alternating
electric currents supplying said branch circuits.
6. The hereinbefore described method of operating motors by alternating electric
currents which consists in raising the field-magnets to a point of high magnetic
saturation while the field-magnet coils are traversed by alternating electric currents
and the motor is at rest or moving slowly, and in gradually decreasing the saturation
of the field-magnets as the motor acquires speed, substantially as described.
7. The combination with the field-magnet and armature of an electric motor, of a
converter having its primary coil supplied with alternating, intermittent or pulsatory
electric currents and its secondary coil connected with the armature coils, a second
converter having its primary coil connected with a source of alternating, inter-
mittent or pulsatory electric currents, and its secondary coil connected with the
field-magnet coils of the motor.
8. The combination with the field-magnet and armature of an electric motor, of a
converter having its primary coil supplied with alternating, intermittent or pulsatory
electric currents and its secondary coil connected with the armature coils, a second
converter having its primary coil connected with a source of alternating, inter-
mittent or pulsatory electric currents, a rectifying commutator upon the armature
shaft of the motor and circuit-connections from the secondary coil of the second
converter through said rectifying commutator with the field-magnet coils.
.9. The combination with the field-magnet and armature of an electric motor, of a
converter having its primary coil supplied with alternating, intermittent or pulsatory
electric currents, and its secondary coil connected with the armature coil, a second
converter having its primary coil connected with a source of alternating, inter-
mittent or pulsatory electric currents and its secondary coil connected with the field-
magnet coils of the motor, and means for varying the ratio of conversion of one of
said converters.

page_text: 10. The combination with the field-magnet and armature of an electric motor, of a
converter having its primary coil supplied with alternating, intermittent or pulsatory
electric currents and its secondary coil connected with the armature coils, a second
converter having its primary coil connected with a source of alternating, intermittent
or pulsatory electric currents, a rectifying commutator upon the armature shaft of the
motor, circuit-connections from the secondary coil of the second converter through
said rectifying commutator with the field-magnet coils, and means for varying the
ratio of conversion of both of said converters.
11. The combination with a source of alternating, intermittent or pulsatory
electric currents and a circuit therefor, of an electric converter having its primary
coil connected in said circuit, a revolving armature having its coils connected in the
circuit of the secondary coil of the converter, a second converter connected with said
source of currents, a field-magnet applied to the armature included in the secondary
circuits of the second converter, and a rectifying commutator interposed in said
secondary circuit between the field-magnet and the converter.
Dated this 22nd day of November 1889.
WM. P. THOMPSON & Co.,
Agents for the Applicant.