IMPROVEMENTS IN ELECTRIC MOTORS AND DYNAMO ELECTRIC MACHINES
Year: 1883

page_text: LETTERS PATENT to Sydney Pitt of Sutton in the County of Surrey, for an
⚫ Invention of "IMPROVEMENTS IN ELECTRIC MOTORS AND DYNAMO ELECTRIC
MACHINES Communicated to me from abroad by Francis Bacon Crocker,
Charles Gordon Curtis and Schuyler Skaats Wheeler all of the City of New
York United States of America
COMPLETE SPECIFICATION filed by the said Sydney Pitt at the Office of
the Commissioners of Patents on the 31st January 1883.
SYDNEY PITT of Sutton in the County of Surrey. "IMPROVEMENTS IN ELECTRIC-
MOTORS AND DYNAMO-ELECTRIC MACHINES "
Communicated to me from abroad by
Francis Bacon Crocker, Charles Gordon Curtis and Schuyler Skaats Wheeler all of
the City of New York United States of America
This invention relates to all such electric motors or other electro dynamic
machines as are actuated by (electric currents supplied to them from unlimited
sources of) electrical energy, that is to say from sources from which currents of
greater or less strength may be derived, according to the amount of power which
it is desired to have developed by the motor, and the object of the invention is to
provide means whereby the power or speed developed by such motors may be
increased or diminished in the most efficient and economical manner.
It is well known that if the electro motive force of such an electric current, or
more properly speaking the electro motive force of the electric generator remain
constant, the strength of the current or the amount of force in the form of electrical
energy which flows through the motor is determined by the electrical resistance of
the circuit (including the resistance of the motor) in which the motor is placed, and
may be increased or diminished at pleasure by altering the said resistance, and
since the power developed by the motor depends upon the strength of current
flowing through it, advantage has heretofore been taken of this fact to regulate the
power of motors by cutting into or out of the circuit more or less auxiliary
resistance in the well known manner Such a method is objectionable, and
materially interferes with the efficiency of the apparatus, for the reason that,
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whenever any such electrical resistance external to the motor is introduced into the
circuit, electrical energy is absorbed by it and transformed into heat without pro-
ducing any useful electro dynamic effect in the motor, and when this external or
"dead
resistance which is thus introduced for the purpose of increasing the
resistance of the circuit, becomes any thing like as great as the resistance of the
motor itself, as it must become in order to reduce the power of the motor materially,
it absorbs a very considerable portion of the total energy in the circuit, and to that
extent impairs the efficiency of the system.
The invention is designed to secure the desired variation in the power or speed
of the motor without entailing this loss of efficiency, not by varying the electrical
resistance of the circuit external to the motor, but by altering the resistance of
that part of the circuit which is comprised in the motor and which produces the
useful electro dynamic effect therein, by which means the strength of current
flowing through the motor may be regulated so as to secure the desired power or
speed without involving the introduction into the circuit of any "dead" resistance
which absorbs the electrical energy without adding any thing to the power of the
motor; the greater part of the resistance in circuit being by the invention confined
to the electro-dynamic coils of the motor in which the electrical energy is trans-
formed into mechanical energy, and where while the motor is working, it occasions
comparatively no loss.
The invention therefore broadly stated consists.
1st In so constructing the field magnets of the electric motor that their internal
resistance may be varied at pleasure.
2nd In so constructing the armature that its internal resistance may be varied
and;
3rd In so combining the armature with the field magnets that the total internal
resistance of the machine as a whole may be varied
The several methods which are employed for accomplishing these objects
consist,
1st In winding the coils of the field magnets, or the coils of the armature of the
electric motor, or both, each with two or more independent wires or conductors
and in connecting the ends of these wires to a circuit-controlling switch by means
of which, one, two, three or more of the said wires may be readily connected in
multiple arc and placed in circuit with the current-supplying conductors.
2nd In connecting the free ends of the said wires or conductors to a circuit
controlling switch of a different construction by means of which the said wires
may be readily connected and the actuating current made to pass through them
"
"
either in "multiple arc or " in groups or "in series" thereby rendering it
possible to regulate the internal electrical resistance of the motor and consequently
the intensity of the current flowing through it, without the introduction into the
circuit of any injurious dead" resistance as more particularly hereinafter set
forth.
"
"
3rd In arranging the connections of the several separate coils or helices which
compose the field magnets in combination with a switch whereby the said several
or in multiple
coils may be connected in circuit either in " series" in "groups
are by which means also the internal resistance is rendered capable of variation
and
4th In so arranging the connections of the armature and field magnets of the
motor in combination with a switch that they may be connected and the actuating
current made to flow through them either in "series or in "multiple arc ALS
"
"
desired whereby the internal resistance of the motor as a whole is changed.
The invention is especially designed to be applied to such electric motors as are
supplied with actuating currents by the well known multiple arc or derived circuit
system of current supplying conductors throughout which a constant electro motive
force is maintained, and in which each motor, whenever operated, is placed in an
independent branch or derived circuit, the resistance of which derived circuit deter-
mines the amount of current which is obtained through each motor. For example

page_text: the invention is especially applicable to the motors of electric locomotives which
require their power to be capable of great reduction after having got under way
and which would otherwise involve the use of a large amount of "dead" resistance
in circuit during the greater portion of the time.
In the accompanying Drawings, Figure 1 represents in elevation an electric-
motor or a dynamo electric machine constructed and provided with a circuit
controlling switch for varying its internal resistance according to the first described
method.
Figure 2 represents in elevation an electric motor or a dynamo-machine similarly
constructed and provided with a peculiar switch for varying its internal resistance
according to the second described method.
Figure 3 is a plan of the latter switch.
Figure 4 represents the invention as applied to the armature of an electric motor
or a dynamo-machine.
Figure 5 represents in elevation an electric motor or a dynamo machine provided
with a switch similar to that shewn in Figures 2 and 3 whereby the several bobbins
of the machine may be connected to the main conductors according to the third
method.
Figure 6 represents in elevation an electric motor or a dynamo machine arranged
to be operated according to the fourth method.
In Figure 1 A represents the armature and F. F. the field magnets of an electric
motor which may be of any well known form of construction. Each of the field
coils is composed of four separate wires or conductors B. C. D. E. which are wound
upon the iron cores one upon another, in such a manner that the wire B forms the
first or inner layer or layers; the wire C, the next layer or layers D, the next, and
so on, the layers extending as usual, the whole length of the coils and the separate
wires being respectively connected at one end to the metallic studs or points
B. C'. D' and E' of the switch S. and at the other end to one of the current
supplying conductors P.
By turning the metal sector or switch S. which is in electrical connection with
the other main conductor N so as to connect it with one two three or all of the
terminals B. C. D'. E. of the field magnet coils at once, the actuating current
may be made to pass through one or more of the wires of the motor in multiple
arc " and so made to produce a stronger or weaker electro magnetic effect, as
desired.
The drawing represents only one of the field coils wound with four separate
wires as just explained, but the other field coil is intended to be wound in a
precisely similar manner with four separate wires having their ends electrically
connected with the corresponding ends of those of the first coil so that the four
separate circuits thus formed lead through both field coils one after the other.
Since the supply of current from the main conductors is practically unlimited
and since the amount of current which passes through each motor depends upon
the resistance of that motor, the effect of adding another of the multiple arc circuits
to one already in connection with the main conductors is practically to double the
power of the motor by doubling the amount of current which passes through it.
This holds true for any number of circuits and therefore when all four circuits
are connected to the main conductors in multiple arc the motive power is
quadrupled.
The reason for winding on only one circuit B at a time, instead of simply
winding the four circuits all together, is in order to have the first circuit wound
the nearest to, the second further from, the next still further, and so on from the
iron core, so as to bring the electric current into the closest possible proximity to
the core, and thereby secure the maximum electro magnetic effect, and hence the
highest efficiency when less than all of the coils are in circuit. If instead of
separately winding the four circuits in this way, I were to wind them all together,
I should have a very bad disposition of the circuits, when the current is only sent
through one two or any number less than all of them, because the wire or wires,

page_text: through which the current passes, and which produce the usual effect are separated
and kept at a distance from the core of the magnet by wires which are lying idle
whereas, if each of the four circuits forms an entire layer, or two or more con-
secutive layers of the coil, whenever we use less than all the circuits to excite the
magnet, I employ those nearest to the cores, and I shall then always have the wires
through which the current passes producing their maximum electro magnetic
effect.
It is obvious that the iron cores of the field magnets may be wound with any
desired number of separate wires or conductors instead of with only four, as repre-
sented and that these wires may be all wound on together side by side instead of
in layers or in any other desired manner. It is also evident that wires of different
sizes may be employed.
Figure 4 shews the application of the same general method to the armature A
of the electric motor or the dynamo-machine, in which the winding of the separate
circuits is not shewn, but is similar to that already described, the first circuit being
wound nearest the core, the second further from it and so on, and each being
separately connected to the strips or points of the commutators G. H. I. J. in the
usual manner precisely as though the other circuits did not exist. It is clear that
by turning the switch S. which is electrically connected with the main conductor N,
one two three or more of the armature circuits may be connected in multiple arc
and so made to increase the range or scope of variation of the motive power, in
addition to that derived from the similar arrangement of the field magnets above
described. After passing through the armature circuits the current emerges by the
commutator brushes reunites and then passes to the field magnet circuits, and then
to the other main conductor.
Figure 2 represents the second method of altering the internal resistance of the
motor, which consists in changing the electrical arrangement in circuit of the
separate wires with which the field magnets are wound. The wires or circuits
themselves are wound upon the magnet cores precisely as in Figure 1 described
above; but instead of varying the power of the motor by sending the actuating
current through one two, three or more of the circuits, as I do in the method shewn
in Figure 1, I secure this variation of power by connecting the field coil circuits in
"series" or in " multiple arc" or in combination of series and multiple are con-
nections, generally called " groups." In Figure 2 I have represented the field
magnets wound with four circuits and in such a case three arrangements or combi-
nations of circuits are possible. First, the four circuits may be connected in
series thus forming a single continuous conductor whose length is equal to the
sum of the four circuits and whose electrical resistance is equal to four times that
of one circuit; second they may be connected in two sets or groups of two circuits
cach, the current passing first through one pair and then through the other, the
result being a double conductor of twice the length of, and having the resistance equal
to that of one circuit; third the four circuits may be connected in multiple arc
thus forming a quadruple conductor, having the length and one fourth the resistance
of one circuit. In order to make these changes in the electrical arrangement
whenever desired according to the invention, I employ a circuit controlling
switch S, of peculiar construction. This switch consists of a revolving cylinder or
drum T formed of some insulating material, into the convex surface of which are
set specially shaped metallic pieces or strips a. b. c. d. &c. and which is provided
with a handle U by which it may be readily turned (see also plan Figure 3).
Against the surface of this drum press eight metallic springs or brushes 1, 2, 3, 4,
5, 6, 7, 8, to which are electrically connected the eight terminals of the four wires
constituting the field magnet-coils of the motor, as clearly indicated. The main
conductors P and N from which the electric current for operating the motor is
derived, are respectively connected permanently to the spring brushes 1 and 8.
We have seen above, that the four circuits may be arranged in three ways:
First, to connect them in "multiple arc" which may be done by turning the
switch-drum T, so as to bring the metal strip a under and in contact with the

page_text: brushes 1, 2, 3 and 4, and the metal strip under and in contact with the brushes
5, 6, 7, and 8 in which case the current enters from the main conductor P and
divides one quarter thereof flowing through each of the four circuits B, C, D, E,
by passing through the strip a then back by the brushes 5, 6, 7, 8, to the strip b,
and by the brush 8 to the return conductor M, thus completing the circuit.
Second, the circuits may be connected in two sets or 'groups" of two each;
this is accomplished by turning the drum T further round so as to bring the
strip under and in contact with the brushes 1 and 2, the strip d under the
brushes 3, 4, 5, 6, and the strip e under the brushes 7 and 8, in which case the
current enters from the main conductor P, flows to the strip c, and then traverses
the field-coil circuits B and C, thence through the brushes 5 and 6 to the strip d,
thence through brushes 3 and 4 and through the circuits D and E then through
the brushes 7 and 8 to the strip e, and thence by the brush 8 to the return main
conductor N.
Third, the four circuits may be connected in " series," and this may be done by
turning the drum T, further around so as to bring the metallic plate h under and
in contact with the brushes 2 and 6, the plate g under the brushes 3 and 5, and the
plate under the brushes 4 and 7, under which arrangement the current enters
from the main conductor P, and first traverses the circuit B (the brush 1 resting
upon the insulating surface of the drum) thence by the brush 6, plate h, brush 2,
through the circuit G, thence to the brush 5, plate g, brush 3 through the circuit D
thence by the brush 7, plate f, brush 4, and finally through the circuit E and
thence by the brush 8 to the main conductor N.
In Figure 2 the armature A is represented as being permanently connected in
circuit in "multiple arc " with the field magnets, in the well known manner, and
in Figure 1 it is represented as being connected in "series" with the field inagnets,
in the also well known manner, but as far as this invention is concerned, the
armature may be connected in both cases either in multiple arc or in series with
the field magnets according as it is desired to bring the current flowing through
the armature under the control of the switch S or to operate the armature on an
independent circuit, and thereby obtain a greater range of control over the field
magnets. It is obvious that the last described method of altering the internal
resistance of the field magnet coils, (illustrated in Figure 2) may also be applied
to the coils of the armature when constructed and provided with separate circuits
as represented in Figure 4 in which case it is only necessary to substitute the
switch shown in Figures 2 and 3, for that shown in Figure 4; but I do not intend
to confine myself to any particular method of varying the internal electrical
resistance of the armature, in order to vary the power or speed of the motor. It
is to be observed that in order to avoid reversing the polarities developed in the
field magnets by any of the circuits wound upon them, the current must be made
to traverse the said circuits always in the same direction whatever the electrical
arrangement of these circuits may be, and this result, the switch shown in Figures
2 and 3 is designed to secure.
In Figure 5, B, C, D, E represent the separate field magnet coils and A the
armature of an electric motor or a dynamo machine.
I have here represented a motor having field magnets composed of four separate
coils, helices, or bobbins, and in such a case as we have seen before three arrange.
ments of these coils in circuit, may be made, according to this invention by means
of a switch similar to that shown in Figures 2 and 3.
First, the four coils may be connected in "series" which is done by turning
the drum T, so as to bring the metallic strips j, k, l, under the brushes 2, 3, 4, 5, 6
and 7; by which the four field coils are connected in "series" to the current
supplying conductors, as will be readily understood from the drawing.
By turning the drum T, farther around so as to bring the next set of connecting
strips m, p, and n, under the brushes, the four field coils are connected in circuit
in two groups of two each, and by turning the drum T still farther around so as to
bring the next set of connecting plates O. S. under the brushes, the four coils are

page_text: connected in circuit in "multiple arc." The path of the current in each case being
clearly discernable from the drawing.
"
In Figure 6, F, F, are the field-magnet coils, and A the armature of an electric
motor of any well known form of construction. The switch S consists of two
parallel swinging switches or bars L and M connected together by a link of some
insulating material, as shown, and of the stationary contact points or studs Q
and O; and the connections are arranged as shown, so that when the switch is
turned upward and the bar L is in contact with the stud O, the path of the current
is as follows: From the main conductor P, through wire i, field magnet coils F F
and wire m, to switch L, thence by wire o through the armature A thence
through wire q, back to the return conductor N, the current in this case passing
through the armature and field magnets "in series," that is in succession and
therefore the resistance of the motor is equal to the sum of the resistance of the
armature and field magnets. When the switch S, is turned downward the bar L
makes connection to the stud G and the bar M makes connection to the stud O
and the path of the current is as follows:-From conductor P to the point R
where the current splits, part passing by wire l, through field coils F, F, wire m,
switch bar L and point Q, to return conductor N, and part passing through
switch bar M. point 0, wire o through the armature A and thence by wire q to
return conductor N, the armature and field-magnets being thus connected in
circuit in "multiple arc," in which case the total resistance of the motor is equal to
the product of the separate resistances of the armature and field-magnets, divided
by their sum.
For example, if the resistance of the field-magnets be equal to that
of the armature, the total resistance of the motor, when connected in "multiple
arc," is one fourth as great, and consequently four times as much current will
flow through it, as if the armature and field-magnets were connected in "series."
It is to be observed that the switch S, is so arranged that the actuating current
always passes through the armature and field-magnets in the same direction,
whether they are connected in "multiple arc or " in series," so that the direction
of rotation of the armature A is not reversed by the operation of the switch S.
In all the methods heretofore described in which either the field magnet cores or
armatures are wound multiply with or are composed of a number of separate wires
or circuits, it is obvious that any number of such wires or circuits may be employed
instead of only four as shown; that such wires or conductors may be of any
desired form, and size, or sizes, and that various combinations or grouping of these
wires or conductors in circuit, either in multiple arc, or in groups, or in series
connection may be made by means of circuit-controlling switches similar to those
herein shown, in order to vary the internal resistance of the motor, without
departing from the invention. The invention not only enables the clectro-dynamic
effect produced by the actuating current upon either the armature or the field
magnets to be varied, at will, by increasing or diminishing the amount of electrical
energy flowing through them, so as to alter to any desired degree the power
developed by the motor without introducing into the circuit any "dead" resistance
external to the motor, or without employing any other inefficient means for
accomplishing the same object; but the invention also secures the important result
of enabling the speed of the motor to be greatly increased, at the same time that
an increase in the power developed in a given time, or in other words, the horse
power of the machine is obtained. An electric motor or electro-dynamic machine
is at the same time a dynamo-electric machine, that is to say, the machine not only
absorbs the current passed through it as a motor, and converts it in mechanical
power, but, owing to the fact that the armature is being revolved under the
influence of the field magnets, it also acts as a dynamo-machine and generates a
current of opposite polarity, technically termed a counter electromotive force,
which more or less neutralizes the direct current and so reduces the power
developed. As the strength of this reverse current or counter electro-motive force, 5
which thus diminishes the strength of the direct current increases with the speed
of the armature, and with the intensity of the magnetic field, as is well known, it

page_text: is evident that, in order to obtain a higher speed without reducing the power of
the motor, it is necessary to increase the power of the armature, and at the same
time to diminish the power of the field magnets, so as to avoid generating an
increased counter electromotive force, and thereby reducing the power of the
machine as a motor.
Hence, when a higher speed is required, some of the electric current actuating
the field magnets should be transferred to the armature, and its electro-dynamic
strength thereby increased and these changes in the relative strengths of the field
and armature are secured by this invention in the most efficient manner, with the
greatest possible economy in the total electrical energy consumed.
It is evident that the methods heretofore described of increasing or diminishing
the electro-magnetic strength of the field of force electro-magnets of an electric
motor or electro-dynamic machine are equally applicable to the field magnets of a
dynamo-electric machine, for the purpose of altering the intensity of the field of
force in which the armature is revolved, and thereby changing the electro-motive
force of the machine, at pleasure, with the greatest possible economy in the electric
current employed to maintain the magnetic-field.
By means of the first described method of varying the internal resistance of the
armature, it is also possible to arrange any dynamo-electric machine so that the
amount of electricity or force in the form of electric current, generated by it, may be
increased or diminished at pleasure, without changing the electro-motive force of
the current produced, and by means of the secondly described method of varying
the internal resistance of the armature, the reverse effect may be obtained, that
is, the electro motive force of the machine, or of the current generated, may be
increased or diminished at pleasure without interrupting the operation of the
machine.
The Invention may be applied to any form of electric motor or of dynamo-
electric machine, and the field magnets and armature or the parts of the machine
which perform equivalent functions, may be constructed, arranged and combined
in any of the many well known ways, for converting electrical energy into
mechanical energy which are best adapted to the work to be done, and the objects
to be attained in each particular case.
What I claim as the Invention and desire to secure by Letters Patent, is :-
First. The method, substantially as herein described, of regulating the power or
speed of an electric motor while it is in operation, by varying its internal electrical
resistance, that is, the resistance of that part of the circuit which is comprised
within the machine and which produces the useful electro-dynamic effect therein.
Second. The method of varying the power of an electric motor, or of a dynamo-
electric machine by altering the internal electrical resistance of its armature, while
it is in operation.
Third. An electric motor or a dynamo electric machine, having its field-magnet
cores, or its armature core, or both, each wound with two or more separately
insulated wires or conductors, substantially as described, said conductors having
one set of their free ends electrically connected together and to one of the current-
supplying conductors, and their other free ends separately connected to a circuit-
controlling switch whereby one, two, three, or more of said field-magnet or armature
conductors may be connected to the other current-supplying conductor in multiple
arc, substantially as and for the purpose set forth.
Fourth. An electric motor or a dynamo-electric machine having its field-magnet
cores, or its armature core, or both, each wound with two or more separately
insulated wires or conductors so that each conductor forms one or more layers,
substantially as described, said conductors having one set of their free ends
electrically connected together and to one of the current-supplying conductors, and
their other free end separately connected to a circuit-controlling switch, whereby
one, two, three, or more of said field-magnet or armature conductors may be
connected to the other current-supplying conductor in multiple arc, in the order of
their proximity to the core, substantially as and for the purpose set forth.

page_text: Fifth. An electric motor, or a dynamo-electric machine, having its field-magnet
cores, or its armature core, or cores, or both, each wound with two or more
separately insulated wires or conductors, in combination with a switch whereby
said wires may be connected with the current-supplying conductors either in series,
in groups or in multiple arc.
Sixth. The combination with an electric motor, or a dynamo-electric machine,
consisting of an armature and field-magnets, of a switch arranged to connect the
circuit of the armature and the circuit of the field-magnets to the current supplying
conductors either in series or in multiple arc, substantially as described.
Seventh. The combination with the separate coils, helices or bobbins, composing
the field-magnets of an electric-motor or dynamo-electric machine, of a switch,
whereby the said coils may be connected in circuit with the current supplying
conductors, either in series, or in groups, or in multiple arc, substantially as
'described.
Eighth. An electric motor having its field magnet cores, or its armature core, or
cores, or both each wound with two or more separately-insulated wires or
conductors, substantially as described, in combination with the switch S whereby
the said wires may be connected with the current supplying conductors, either in
series or in groups or in multiple arc, substantially as described.
Ninth. The combination with the separate coils, helices or bobbins, composing
the field magnets of an electric motor, of the switch S whereby the said coils may
be connected in circuit with the current-supplying conductors, either in series or in
groups, or in multiple arc, substantially as described.
Tenth. The method, substantially as herein described, of regulating the power or
speed of an electric motor by varying its internal electrical resistance, that is, that
part of the circuit which is comprised within the machine, and which produces
the useful electro-dynamic effect therein, without changing the construction of the
machine.
Eleventh. The method of varying the power of an electric motor by altering
the internal electrical resistance of its moving armature, without altering its
construction. ;
In witness whereof I the said Sydney Pitt have hereunto set my hand
and seal this thirtieth day of January in the year of our Lord One
thousand eight hundred and eighty three.