IMPROVEMENTS IN MEANS FOR REGULATING ELECTRO-DYNAMIC, MOTORS
Year: 1884

page_text: I THOMAS JOHN HANDFORD of 42 Southampton Buildings in the County of
Middlesex Patent. Agent do hereby declare the nature of the said invention for
"IMPROVEMENTS IN MEANS FOR REGULATING ELECTRO-DYNAMIC, MOTORS" a com-
munication to me from abroad by Frank Julian Sprague, of New York in the
County and State of New York United States of America Electrician to be as
follows:-
The object of this Invention is to regulate the speed of Electro-dynamic motors
and the available power derived therefrom, and to readily reverse the motion of
the same.
This regulation is accomplished by dividing the coils of the field magnet of
the machine into sections, placing the armature in a shunt around a variable
number of such sections, and providing means for varying the number of such
sections around which the armature is shunted the said armature remaining in
series with the rest of the sections.
Thus the difference of potential between the terminals of the armature circuit is
varied, and the speed and power of the motor is thereby regulated. The same
commutator by which these connections are changed may be so arranged as to be
used also to reverse the current through the armature coils in order to change the
direction of rotation of the motor.
In combination with the coils divided into sections I may employ also supple-
mental field coils connected in series or in parallel circuit with the armature, and
whose connections are not varied. Or I may use in combination with the coils
divided into sections certain independent field coils connected directly with the
supplying circuit and which may have independent current regulating devices
connected with them such for example as a multiple contact switch or range of
break circuit switchies the depression of any of which cuts out a certain number
of the coils. On such supplemental coils and independent coils may be used
together in combination, with the coils divided into sections as hereinbefore
referred to.
In the simplest form of my invention one end of the armature circuit is
connected with a contact arm arranged to travel over a range of contact blocks,
thereby making electrical connection with different sections of the field coils.
The other end of the armature circuit is connected with one end of the series of
field coils, such connection being made at the junction of such series with the
supplying circuit or at any other convenient point.

page_text: As the arm moves over the successive contacts the armature is shunted around
a greater or less number of the sections of field coils and the difference of potential
between the terminals of the armature circuit is varied to the desired extent.
When it is required to reverse the current in the armature without reversing the
connections, the field magnet sections are connected to a circular range of contact
pieces, and a double arm is used the two parts of which are insulated from
each other and bear on opposite blocks of the contact range The two arms are
connected respectively to the two terminals of the armature circuit, and as the
arms are made to travel around the contact range the difference of potential
between the armature terminals is reduced from the maximum to zero, then the
circuit is reversed and then if the movement is continued in the same direction, the
difference of potential increases again.
The connections are made: the first and last sections of the field coils respec-
tively to single and opposite blocks of the range: the next adjacent sections have
each a double connection to the two blocks on either side of the blocks first
connected, the next sections to the next pairs of blocks, and so on until the
connections meet on the two opposite sides of the range.
Or the field coil sections may be divided into two sets or series and connected
respectively to the blocks of two ranges of contact pieces. Upon each range
travels an arm and the two arms are connected respectively to the two terminals
of the armature circuit the armature being thus in a shunt between the series of
field coil sections.
The armature current may be changed and reversed by moving the arms along
the contact ranges. The movements of the contact arms may be accomplished by
hand or automatically by means of mechanism controlled by variations in. the
speed of the motor.
I employ in preference as an automatic arrangement a suitable primary governor
operated by changes in speed and secondary mechanical apparatus thrown into
action by the movements of said governor the said secondary mechanism operating
the contact arms.
A convenient form consists of a centrifugal governor on or connected with the
armature shaft of the motor, whose movement in one or the other direction sets
in motion a train of gearing which is connected with the contact arm or arms
controlling the circuit. Or two opposite bevel wheels may be employed one
connected with the motor shaft the other with a separate source of power of
constant speed. The bevel wheels act to move a shaft or spindle in opposite
directions which shaft or spindle carries the contact arm or arms. Variations in
the speed of 'the motor above and below the speed of the opposing constant power
cause the shaft to move and the contact arms to vary the circuits in the proper
direction.
Or other equivalent automatic means may be used to operate the arm or arms as
for example the tightening or loosing of a brake, the throwing into action of an
arm baving reciprocating motion, or the actuation of an air, water, steam or
electric motor as will be well understood.
It is obvious that the automatic means or devices may also be used to vary
adjustable resistances or otherwise to affect circuits for regulating motors.
It is also evident that the principle of my Invention is equally applicable to a
system of three or more conductors as to two conductors and with motors connected
in series or otherwise.

page_text: I THOMAS JOHN HANDFORD of 42 Southampton Buildings in the County of
Middlesex, Patent Agent, do hereby declare the nature of this invention for
"IMPROVEMENTS IN MEANS FOR REGULATING ELECTRO-DYNAMIC MOTORS" and
in what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement:-
The object of the said invention is to regulate the speed of electro-dynamic
motors and the available power derived therefrom and to readily reverse the motion
of the same.
This regulation is accomplished by dividing the coils of the field magnet of the
machine into sections, placing the armature in a shunt around a variable number.
of such sections, and providing a suitable commutator for varying the number of
such sections around which the armature is shunted the said armature remaining
in series with the rest of the sections. Thus the difference of potential between
the terminals of the armature circuit is varied and the speed and power of the
motor are thereby regulated.
The same commutator by which the circuits are controlled may also be used if
desired to reverse the current in the armature circuit.
The principle of the said invention and the different arrangements employed in
carrying out the same are illustrated in the accompanying sheet of drawings the
same letters of reference indicating corresponding parts in all the figures.
Figures 1, 2, and 3 are diagrams illustrating the principle of the invention.
Figures 4, 5, 6, 7, 8, 9, 10, 11, 12, 12ª, 14 and 15, are diagrams showing motors
embodying the said invention and variously wound and connected.
Figures 13 and 16, illustrate automatic regulating arrangements.
The generator which supplies current to the motor is shown in figures 1 and 4
only. In the other figures it is understood that the main conductors extend to and
from such a generator.
In figure 1, D' is the generator and C, C', are main conductors extending
therefrom. A derived circuit p p' extends across the said main conductors. The
current energizing the field of the generator may be ignored. It is evident that a
current will flow over the circuit p p¹ proportioned to the difference of potentials
at its terminals and inversely proportional to its resistance.
Now if it is desired to use current at the point p' and to vary such current, we
must be able to vary the resistance of the shunt circuit pp, p², or vary the
difference of potential between the terminals p and p2. If the point p* be moved
along p, p¹, the difference of potential may be varied to any desired extent and
consequently the current obtained at p may be varied from the maximum to zero.
Instead of moving one terminal p³ to p³ both terminals can be made to approach
each other, and after passing to recede from each other. If this is done the current
in p pp, will decrease gradually to zero, then begin to increase, but flowing now
in the opposite direction, so that the maximum and minimum currents with change
of direction can be attained without making or breaking any circuit and in a
perfectly progressive manner.
In Figure 2, this arrangement is shown where the conductor p, p³ pl' and the
shunt p p p are in the main circuit, that is a series arrangement. Precisely the
same effect can be produced as described in reference to Figure 1, if the terminals p
be made to approach or recede from p¹, or if p³ p¹ be made to approach, pass and
recede from each other,

page_text: In figure 3 an arrangement embodying the principle of the Wheatstone Bridge is
illustrated.
Let a p' and p b p¹ be two circuits and a ba shunt circuit between them-
If a b has the dotted position pp¹, the maximum current will flow as indicated.
As a approaches the position a¹ and b that of 61, the current in b diminishes, and
when occupying the position a¹ 61, that is with equal ratios of resistance in the two
parts of the conductors p a p¹ and p b p¹ no current at all flows. As a passes a
to a and b passes 61 to 6%, the current again flows in a b as indicated in 6, a³, that
is in the opposite direction to what it had before and as a' comes to p' and b² to p
the maximum reverse current is attained. Here too there has been a perfectly
progressive change of strength and direction of current in the shunt conductor.
If any other independent circuit joined p, p¹, the current in these independent
circuits would be independent of the change in the circuit considered provided p
and p remained at the same difference of potentials. There would be a change in
the currents flowing in the different parts of the conductors p a p' and p b p¹ but
it is just now unnecessary to enter into what would be an elaborate mathematical
consideration of this.
The relative changes in all these circuits would depend upon the difference of
potentials existing at the mains C, C, and the resistance of the several circuits. If
for any reason a counter electro motive force were set up in the shunt circuit the
currents flowing in the several parts would be materially modified but the current
in the shunt more than in the direct circuits.
It will be noticed that the variation of currents in the shunt circuit was attained
without the introduction of any resistance into the shunt circuit proper, or the
throwing in or out of any resistance at all.
In embodying this principle in the regulation of an electro dynamic motor the
field circuit of the motor takes the place of the circuit p p³ p¹, of figures 1 and 2, or
two field circuits the place of the conductors p a p¹ and p b p¹ of figure 3; and the
armature circuit takes the place of the shunt circuit p p p³ in figure 1; p¹, p* p³ in
figure 2, or a b, a¹ b¹ or a b³ of figure 3. These field circuits may if necessary be
supplemented by others which may be connected with the armature circuit or may
receive the current directly from the mains.
I have shown in the drawings a number of different modifications embodying
the same principle and which I will proceed to describe in detail.
Referring to figure 4, D¹ is any suitable generator and C, C¹ are main conductors.
The motor D derives current through the circuit e d from these main conductors.
F is a range of field coils divided into sections and F' a supplemental set of
coils. A is the armature, and n n¹ the commutator brushes. R is a range of
contact blocks and is a pivoted contact arm travelling thereon.
Current entering at e divides at e¹³, part passing direct to d through the coils F
and the rest through the sectional coils F to c where it again divides, part
passing on to d and the rest to contact block c¹, arm l, brush n, armature A and
brush n¹ to d.
It will be readily seen that the armature is in series with all the sections F to the
right of the dividing point c in the drawing, and in shunt relation to the sections F
on the left of that point. Now by moving the arm 7 the dividing point is changed,
the number of sections around which the armature is shunted is varied, and hence
the difference of potential between the armature circuit terminals is changed. The
motor is thus regulated without breaking circuit and without the use of an
adjustable resistance or other apparatus wasteful of energy In this arrangement
the coils F¹ on the lower limb of the magnet are also in shunt relation to the
armature.
In the modification shown in figure 5 all the field magnet coils F are divided into
sections. Current entering at e divides at c. Part passes on through all the rest of
the coils F to d. The remaining current passes through contact c¹ and arm to the
armature and thence to d. By moving the arm 7 the same effect is produced as in
the previous instance,

page_text: In figure 6 supplemental field coils F¹ are employed placed in series with the
armature. From dividing point c, part of the current passes through contact c¹ to
the armature and thence through coils F¹ to d. The rest of the current after
passing through the remaining field coil sections goes direct to d.
In figure 7 connection is made direct from the arm to supplemental coils F1 and
direct from the armature to point d, the supplemental coils being thus placed in
parallel circuit to the armature.
Figure 8 is on the Wheatstone Bridge principle set forth in connection with
figure 3. The armature is in a shunt between two ranges of sectional field coils, F, F,
and in parallel circuit with supplemental field coils F¹.
Current enters at e divides at s whence it has two paths direct to d over the two
Bectional ranges of field coils F F-At point c however part of the current is
shunted off, due to whatever difference of potentials exists between c and c³. This
shunted current passes over cc¹l and g (the arms and are of course insulated
from each other) where it divides, part passing. over n, A, and n¹, to g¹ and the
other part over h, F¹ and h³, to g¹ whence the united parts flow over to c³ on the
second range.
Arms and determine not only the difference of potential existing but also
which terminals shall be the highest. If passing the zero point it would be
necessary to shift terminals h h¹.
Figure 9 represents a Wheatstone Bridge arrangement the same as in Figure 8.
with the exception that instead of the armature being in parallel circuit with the
supplemental field coils the current after leaving 7 passes through the armature
coils and supplemental field coils in series over the path n A n¹ h¹ F¹ h to l¹-The
armis perform the same function as in Figure 8, and the same necessity arises for
changing the connections h h¹ if changing the direction of current. Of course this
change can be automatic.
Figure 10 represents a simple Wheatstone Bridge arrangement without any
supplemental coils; the whole of the shunted current passes through the armature
over the path 1, n, A, n¹, to l'. The arms, as before, determine the potential and
direction of rotation.
In all the arrangements thus far shown and described, it is necessary to reverse
the connections in order to change the direction of motion of the motor armature.
I will now describe an arrangement by means of which the current can be reversed
as well as varied by the same commutator.
Figure 11 represents such an arrangement. In this figure all the field coils F F
are divided into sections These sections are connected in the following manner to
the circular range of contact pieces R¹. The first or connection nearest the main C,
The next
is joined to one block o: likewise the last one to the opposite block o*.
connection on bight c, is joined to the two adjacent blocks o¹ o¹ on either side of o;
likewise the next to the last connection or bight to the corresponding blocks on the
opposite side. The next succeeding bight, the third, is joined to the next adjacent
blocks on either side, o³, o³, and so on. As the arms are rotated the actual points
in electrical connection with land l'approach each other. When on o and o" the
maximum difference of potential exists. At right angles to this position there is no.
difference and as the arms are rotated in the same direction, the potential is reversed
and increases in difference till when a half revolution is completed, the maximum
reverse potentials exists at 1, 1, and so on. As shown the current enters at e
passes around F, F, and out at d, but at ca part is shunted off and passes
over c, o¹, l, n, A, n¹, l, o¹, c³ to d.
,
It is evident that supplemental coils may be introduced into the armature,
circuit, in series or in parallel circuit with the armature coils as shown in
Figures 8 and 9.
In the form illustrated in figure 12 an additional element appears, viz
independent field coils f. f, which are connected directly with the supplying
circuit and are not varied by the commutator. This figure is otherwise similar to.

page_text: figure. 11.
It is evident, of course that these independent coils may be used in
connection with any of the arrangements shown in the preceding figures.
Figure 12 shows these independent coils ff, and also supplemental coils F¹ in
series with the armature.
Many other modifications of field coils may be made and other forms of field
magnets used, but it is not thought necessary to describe them in detail. The
number of convolutions in each of the sections the resistances et cetera may be such
as to give the best electrical arrangements, and hence are not necessarily equal-
Hence it follows that high and low resistance coils may be used in series, and the
low resistance ones only be sectional if so desired.
The one common principle in all these modifications is the employment of a
range of sectional field coils and the variation or reversing by progressive steps by
means of a suitable commutator of the difference of potential existing at the
terminals of the armature circuit and consequently the current flowing therein, by
electrically connecting such terminals to different parts of the sectional field coils;
and one or more armature or armatures circuits as well as one or more ranges or
sets of field coils can evidently be used.
'
Whilst varying the potentials and current in the armature and fields as
proposed, it may be requisite to vary the strength of the field magnets in-
dependently.
Figure 14 illustrates a method of accomplishing this where the sectional
arrangement is the same as in Figure 11-The method proposed is to wind a part
of the field magnets with several distinct coils joined in parallel circuit. These
coils may be wound together or separately They are shewn in the figure as
separate ff1, f11, ƒ¹, ƒ ƒ
At one terminal they are joined permanently d² d³. At the other by a multiple
contact switch or by a range of break circuit switches, the depression of any of
which cuts out all the coils to the right of it. In the figure, three of the sets are
cut out by depressing the switch as shown. This of course may be used with any
of the modifications of field coils described.
The modifications described have been shown applied to a system of two
conductors. It is evident that the same principles are applicable to a system of
three or more conductors and with even a greater variety of local arrangements.
Figure 15 shows two such arrangements. Two motors are joined in series, C
and C¹ being the main supply conductors and C" a third conductor which may or
may not be in action, it being rather a safety or balance conductor than a main
supply.
The upper of the two motors has a sectional range of field coils F, F, supplied
from the external mains C, C'. One terminal of the armature circuit is joined to
the middle conductor and the other end to the arm in contact with R. By this
arrangement the movement of 7 not only changes the amount of the difference of
potential at the terminals, of the armature circuit, but reverses it, the position of
zero potential being when the arm is on the middle block.
In the lower motor, the same arrangement of circuits obtains as explained with
reference to Figure 12, except that the range is between the two extreme
conductors C, C, and the independent circuit between one of the extremes C¹, and
the middle one C-Any of the arrangements previously described for a system of
two conductors may be used with either of the two sets of conductors of a system
of three conductors such as is shewn in Figure 15.
It should be observed that the Invention is more particularly applicable to
electric locomotives its primary object being to secure full control of the armature
current under all circumstances whether the lomomotive is at rest or in motion.
The regulation may be readily effected by hand as required; or a constant speed
of the motor may be maintained by automatically changing the relation between
the number of field coils in series' and in shunt relation to the armature.
Figures 13, and 16 represent two modifications of automatic mechanism adapted
for this purpose cate
'

page_text: In Figure 13, D is the motor: F F field magnet coils wound in sections the
bights being connected to the range of contact pieces R; iji a centrifugal governor
with removable collar u, the governor receiving motion from the armature A,
through belt w and bevel wheels kk. The belts vv communicate motion to two
toothed wheels q q¹ mounted in the frame S.
This frame supports another wheel q³ and an arm r carrying another small
wheel q which engages ³ and is connected by an adjustable joint r¹ to the
collar u
According as u rises or falls the arm is carried up or down and q³ engaging q
or q communicates motion in one way or the other to q³ and thence to the
adjustable arm 7; this motion continues until the speed is restored to the normal,
when q is left free. A tangent screw T allows an independent setting of the
arm l
In figure 16, M, M¹, are two opposite bevel wheels the former being operated
from the motor armature through belt m and the latter from an independent source
of power through belt m¹. These bevel wheels engage with the small bevels N N¹
on the loose spindle P connected to land as the speed of the motor varies the
arms are moved upon the contact range R¹ as above explained.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed declare that what
I claim is :-
1st In regulating electro-dynamic motors, constructing the motor with a portion
or all of its field magnet coils divided into sections, its armature coils in a shunt
circuit around a variable number of such sections and in series with the remainder,
and a suitable commutator by which the relation between the number of coils in
series with the armature and the number in shunt relation thereto may be varied
as required, or which accomplishes not only this variation but also the reversal of
the armature current all substantially, as hereinbefore described.
2nd The combination of two ranges of sectional field coils, the armature in a
shunt circuit between the ranges, means for changing the connections of the
armature circuit terminals from one field section to another, and means for
reversing the currents in the armature circuit, all substantially as hereinbefore
described.
3rd The use of supplemental or independent field coils or of both supplemental
and independent field coils in combination with the variable field sections and the
armature in a shunt around such sections, the independent field coils being
provided or not with regulating means, all substantially as hereinbefore described.
4th Maintaining a constant speed in electro dynamic motors by automatically
changing the relation between the number of field coils in series and in shunt
relation to the armature substantially as herein before described.
5th The peculiar mode of connecting the field magnet coils to the commutator
substantially as hereinbefore described with reference to Figure 11 of the accom-
panying drawings.