Improvements are also Applicable to the Regulation of Dynamo Electric Generators.
Year: 1885

page_text: of which Improvements are also Applicable to the Regulation
of Dynamo Electric Generators.
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 AND RELATING TO ELECTRO-DYNAMIC MOTORS PARTS OF
WHICH IMPROVEMENTS ARE ALSO APPLICABLE TO THE REGULATION OF DYNAMO
ELECTRIC GENERATORS," a communication to me from abroad by Frank Julian
Sprague of New York in the County of New York and State of New York,
United States of America, Electrical Engineer, to be as follows:-
This invention relates mainly to the regulation of electro dynamic motors, and
has for its object the providing of a complete system of regulation whereby the
power developed at any given speed or the speed at any given power may be
varied either automatically or by hand with the greatest readiness and precision ;
the speed may be maintained constant under varying loads; and the commutator
brushes may be automatically maintained at the non sparking points.
My said foreign correspondent has shown in the provisional specification
accompanying my former application for Letters patent dated the 29th November
1884 N° 15768, that with any given potential at the armature terminals a constant
speed may be maintained under varying loads by varying the strength of the field
inversely with the variations in load, so that when the load diminishes the counter
electro-motive force is increased, whereby the speed remains the same, and vice
versa. By similar variations in the field, also, the motor was made to develope the
same power per unit of time at different speeds.
A portion of the present invention relates to a method of regulating the field of
the motor for the purpose just mentioned.

page_text: In the Complete specification to former Letters patent granted to me dated the
28th January 1884 N° 2266 is shown the motor armature shunted around a
variable number of field coils, the armature current being varied by shifting its
terminals along the variable field coils.
The present arrangement for regulating the field is similar in principle to this.
It consists in the use of an additional series of field coils shunted around the
sectional field coils, and having means for varying the number of field coils around
which it is shunted, it remaining in series with the rest.
It is evident that if the potential in the mains remains of the same polarity the
magnetic effect due to the variably shunted coil will vary, being cumulative, nil or
differential according to the position of the terminals of the said coil, and it is
further evident that by shifting such terminals the free magnetism of the core can
be varied from the maximum practical saturation to nothing, or can be reversed,
and this in a perfectly progressive manner. Thus the strength of the field may be
regulated or varied to any desired extent and with great readiness and nicety; and
since the energy expended in the field if it is properly wound and constructed is a
very small part of the whole amount used, this method of regulation is a very
economical one. By the use of automatic mechanism such for example as a
solenoid placed in the armature circuit and having its movable core drawn back
by a spring, or a polarized armature, or equivalent devices to shift the terminals
of the shunted coils the speed of the motor may be kept practically constant under
varying loads.
It is evident that this method of regulating strength of field is applicable also
'to dynamo electric generators.
A combination, in a motor, of this method of field regulation with means for
varying the potential at the armature terminals, preferably such as has been above
referred to, gives a remarkably wide range of operation Both the shunted field
coil and the armature may be regulated by the same commutator, or different
commutators may be used.
Also the armature and shunted field coil may be each operated upon a different
range of sectional field coils.
Another part of the invention relates to the use as a means of regulation, of a
field coil wound to oppose the main field coils, which is placed in series with the
armature, the latter being if so desired shunted upon sectional field coils.
The differential coil is preferably of low resistance and few turns and it may
have reversible terminals so that it can be made a differential coil still, if the
armature current is reversed.
To explain the operation of this it may be considered when used as the only
means of field regulation without the variably shunted field coil.
With given initial and armature potentials, number of turns etcetera, there will
be a direct magnetic effect due to the regular or sectional field coils which may be
expressed by the amperes flowing in such coils multiplied by the number of turns-
and there will be a negative effect produced by the armature field coils which
may be expressed by the amperes flowing through the armature multiplied by the
number of turns in said coils. This gives a differential field which may be expressed
by the difference in number of ampere-turns of these two factors. Suppose the
load upon the armature, under which it is running at some particular speed, to be
diminished. The armature will increase its speed slightly, the counter electro-
motive force will be increased and the current flowing in the armature and in its
field coil will be diminished. This however immediately decreases the negative
effect of the differential coil, and the positive or direct field becomes more predomi-
nant, the field is strengthened, and the counter electromotive force is increased
which further diminishes the armature current and the negative effect of the field
coil and so on.
That is, the regulating influence thus employed to govern the motor and prevent
its racing, is cumulative being set in action by a slight increase in speed and
augmented by an increased field due to the diminished influence of the differential

page_text: coil whose influence depends upon the armature current. Oppositely, a slight
decrease in speed causing a diminised counter electro-motive force, increases the
effect of the differential coil, and diminishes the field.
With the motor running free, this coil will become practically dead and its
influence nothing, but it is ready to automatically come into action the instant any
load is placed on the motor.
It will be seen that with a motor running at a high efficiency the change in
speed, provided the mass of iron in the core is sufficiently quick in changing its
magnetic state with a change in current need be very slight.
The differential coil may however be placed outside the terminals of the
armature and main field shunts. In this case it is of course still in series with
the armature.
A motor so arranged is preferably used on a circuit of constant difference of
potential because in a circuit of constant current the motor must work at less
than 50 per cent arniature efficiency which is uneconomical and therefore commer-
cially impractical.
On the two kinds of circuits the action of the motor is totally different. On a
constant potential circuit the drop in the potential between the line terminal and the
terminals of the armature and main field shunts-where the series coil is situated―
varies with the load on the motor, and the differential effect of said series coil
therefore varies with the load; while in the constant current circuit the current in
the series coil, so situated, is constant, and so its differential effect is not varied
and the motor will not regulate except as stated when working at less than 50 per
cent efficiency.
But the differential coil can be used as the sole means of regulation, only in
motors constructed for particular work and speed, for the two sets of coils must be
properly proportioned in constructing the machine to enable them to produce all
the different effects from the maximum to the minimum of field strength which
must be obtained in practice.
To apply the principle to a general system of regulation of power and speed of
a motor to meet the various conditions which occur in practice both mechanical
and electrical my said foreign correspondent prefers to combine it with the
independent coils shunted around more or less of the sectional coils which is set
forth above. Preferably also means are used for varying the armature current.
Having these methods of field regulation combined the field can be adjusted by
means of the shunted coil to the particular work which the motor has to do at
any time the series field coil will then act while the motor is running to regulate
for any changes which occur.
As has been suggested, the magnetic effect of the field coils on the cores may be
expressed by "ampere turns." For a certain range of variation the magnetic
field will be proportional to the ampere-turns, but this law will not hold when the
iron approaches saturation. Consequently, a given ratio of increase of ampere
turns will not always give the same ratio of increase in counter electro motive
force for all given initial speeds, and more particularly will not a given numerical
increase of ampere-turns give the same ratio of increase in counter electro motive
force at different speeds. Also the ratio of increase of counter electro-motive force
from maximum to minimum load depends upon the determined ratio with the
initial electro-motive force of which the counter electro-motive force shall for the
time be considered the normal, which, other conditions being equal depends on
the load. As has been shown above the use of an independent differential field
coil gives the ability to use any desired number of effective ampere-turns for
the field.
Hence if a differential coil in the armature circuit is used it is best to have
means for varying its influence.
This may be done by cutting out more or less of the turns or by throwing more
or less of them into parallel circuit with each other.

page_text: My foreign correspondent however prefers to divide them into two sets one
being sectional and the other having its terminals adjustable upon the sections
precisely as hereinbefore described for the main field coils.
The differential series field may be used in connection with any automatic means
for accomplishing the other described regulations.
By the foregoing arrangements and combinations the most absolute and positive
control of an electric motor as regards speed and power is secured either in hand or
automatic regulation up to the mechanical limit of its construction and the electrical
capacity of the circuit."
For the complete regulation of a motor, however, one more element is required,
viz the automatic adjustment of the commutator brushes to the non-sparking points
of the commutator cylinder; a portion of the invention consists in the providing of
.means for this purpose.
Many different methods have been proposed for shifting automatically the
brushes of a dynamo electric generator for different purposes; no one of these
bowever is adapted for use with an electro-dynamic motor.
One proposed method is to keep the brushes at such points as will give a constant
potential with a varying lead as in some incandescent electric light circuits. This
does not keep them at the non-sparking points. Another is to differentiate the
action of three or more armature coils to maintain a constant current. This does
not prevent sparking. A third proposes the use of one or more accessory brushes
and regulating apparatus in the circuit between the accessory and the main
collecting brushes. Such apparatus would equate the potentials at the main and
the accessory brushes and would not keep either at the true non-sparking point.
Another method makes the movement of the brushes depend upon the armature
current to give a positive lead in the direction of rotation. In this connection the
marked difference may be pointed out between the action of generators as ordinarily
wound with continuous armature windings of the Paccinotti or Alteneck systems
and motors similarly wound, and such as will be used in. practice.
Dynamos may be generally classed as series or shunt machines. In both, if the
speed is increased with a fixed external resistance the field and the electro-motive
force are both increased and the brushes must be given an increased lead in the
direction of rotation. In a machine for incandescent lighting, generally excited on
the shunt system a decrease of external resistance is attended with an increase of
current and a lead is given to the brushes in the direction of rotation.
All methods of automatic regulation of brushes on this principle with which my
said foreign correspondent is acquainted depend for the positive movement upon
the current in the armature which is the total current in the circuit.
Two distinct influences however determine the proper position for the brushes
and these influences are differential.
With any given field the displacement is fairly proportional to the current in
the armature.
With a given armature current and displacement if the strength of field is
increased, the displacement is diminished.
Now in a dynamo, the variations in the strength of the armature current and
of the field are of the same character both being increased or both being diminished
by the same causes though not necessarily in the same ratio..
In a motor designed to run at any given speed with varying loads and regulated
in any way by the field the armature current and the strength of the field must
vary inversely and whatever the lead given to the brushes it is a negative one.
A further destinction between generators and motors is that in the generator the
direction of the current in the field is opposed to that in the armature; in the
armature the current flowing toward what is ordinarily termed the positive brush
and in the field away from it, while if the machine is used as a motor to run in
the same direction the direction of the current in the field may remain the same
while that in the armature is reversed which of course reverses the polarity of the
armature.

page_text: In the dynamo the field is properly a part of the external circuit and after
polarization there can be no reversal of a self excited dynamo except by a reversal
of the direction of rotation and shifting of the field terminals, and such. reversal of
direction would reverse the lead of the brushes and shift the non-sparking point to
the opposite side of the middle position.
In a motor with shunt or series field, the polarity of the terminals of the machine
can be reversed as rapidly as desired without changing the direction of rotation or
the lead of the brushes.
If a dynamo with an electro magnetic device for shifting the brushes be used as
a motor to run in the same direction the action of the shifting device will cause
the brushes to spark badly and the entire reversal of its action would be necessary.
From the above it will be seen that no method which has been used of shifting
the brushes of a dynamo to the non-sparking point can be employed for the same
purpose with an electro-dynamic motor.
In motors in which the field magnet is not regulated the brushes may be
regulated by the variations in armature current alone, an electro magnetic device
being placed in the armature circuit and connected with the brushes so that an
increase of armature current causes the shifting of the brushes, to increase their
negative lead.
But in a motor in which the field magnet strength is varied to change the speed
it is necessary to also cause this variation of the field to affect the brushes so that
an increase in field strength acts oppositely to an increased armature current-
that is it diminishes the negative lead of the brushes. For as the magnetic field
is due both to the armature and the field magnet strength, a variation in either of
these factors causes a change of the non-sparking point and necessitates the shifting
of the brushes.
The method of regulation for the brushes which forms part of this invention
consists then in automatically increasing the negative lead of the brushes simul-
taneously with an increase of the arinature current (and vice versa) and decreasing
automatically the negative lead simultaneously with an increase of field magnet
strength (and vice versa).
In practice for motors in which the field is varied my said foreign correspondent
prefers to employ as a brush shifter an electro-magnetic device in which armature
and field magnet currents oppose each other so that an increased armature current
and a decreased field current have the same effect on the brushes.
My said foreign correspondent has devised several different brush-shifting devices
acting on these principles.
In some of these the electro magnetic brush shifting device is included in the
armature circuit and in the main field circuit, in others in the armature and
independent field coil circuits; and in others in all three of these circuits. And in
one apparatus the armature current is made to act in two directions on the brushes
so that the effect is the same no matter in which way the current is sent through
the motor.
A centrally pivotted arm carries the commutator brushes which bear on the
commutator. Upon the arm is a polarized armature, situated between two curved
pole magnets the coils of both of which are in the armature circuit. When the
armature current is in one direction, armature moves toward one magnet and when
in the other direction toward the other magnet. An arm extends below the
armature and carries the core, upon which are wound two coils included one set in
circuit of the main or sectional field coils, the other in the circuit of the inde-
pendent variably shunted field coils. These field circuit coils tend to hold the
polarized armature centrally, but armature circuit coils tend to move it in one
direction or the other. One of the field circuit coils will be omitted in a motor
having a simple field circuit provided with a current regulating device and then
the position of the brushes depends upon variations in the main field strength and
in the armature current.

page_text: It is to be understood that it is not necessarily for an increase in field current but
for an increase in field magnet strength that the negative lead of the brushes is
diminished.
An extended portion of the field magnet might be used in some cases to oppose
the electro-magnetism established by the armature current.
I THOMAS JOHN HANDFORD of 42 Southampton Buildings in the County of
Middlesex, Patent Agent do hereby declare the nature of this invention and in
what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement :—
This Invention relates mainly to the regulation of Electro-Dynamic motors, and
bas for its object the providing of a complete system of regulation whereby the
power developed at any given speed or the speed at any given power may be
varied either automatically or by hand and with the greatest readiness and
precision; the speed may be maintained constant under varying loads; and the
commutator brushes may be automatically maintained at the non sparking points.
My said foreign correspondent has shown in the specification to former Letters
patent granted to me on his behalf dated the 29th November 1884 N° 15,768 that
with any given potential at the armature terminals a constant speed may be
maintained under varying loads by varying the strength of the field inversely with
the variations in load, so that when the load diminishes the counter electro-motive
force is increased, whereby the speed remains the same, and vice versa. By
similar variations in the field also, the motor was made to develope the saine power
per unit of time at different speeds.
A portion of the present invention relates to a method of regulating the field of
the motor for the purpose just mentioned.
In the complete specification to former Letters patent granted to me dated the
28th January 1884 N° 2266 is shown the motor armature shunted around a
variable number of field coils, the armature current being varied by shifting its
terminals along the variable field coils.
The present arrangement for regulating the field is similar in principle to this.
It consists in the use of an additional series of field coils (independent, of the

page_text: armature circuit) shunted around the sectional field coils, and having means for
varying the number of field coils around which it is shunted, it remaining in series
with the rest.
It is evident that if the potential in the mains remains of the same polarity, the
magnetic effect due to the variably shunted coil will vary, being cumulative, nil or
differential, according to the position of the terminals of the said coil, and it is
further evident that by shifting such terminals the free magnetism of the core can
be varied from the maximum practical saturation to nothing, or can be reversed,
and this in a perfectly progressive manner. Thus the strength of the field may be
regulated or varied to any desired extent and with great readiness and nicety; and
since the energy expended in the field, if it is properly wound and constructed, is
a very small part of the whole amount used, this method of regulation is a very
economical one. By the use of automatic mechanism to shift the terminals of the
shunted coils the speed of the motor may be kept practically constant under
varying loads.
It is evident that this method of regulating strength of field is applicable also to
Dynamo-electric generators.
A combination in a motor of this method of field regulation with means for
varying the potential at the armature terminals, preferably such as has been above
referred to, gives a remarkably wide range of operation Both the shunted field-
coil and the armature may be regulated by the same commutator, or different
commutators may be used.
Also, the armature and shunted field coil may be each operated upon a different
range of sectional field coils.
Another part of the invention relates to the use as a means of regulation in
combination with independent field coils variably shunted upon the main field coils
as before mentioned, of a field coil wound to oppose the main field coils, which is
placed in series with the armature, the latter being if so desired shunted upon
sectional field coils. The differential coil is preferably of low resistance and few
turns and it may have reversible terminals so that it can be made a differential coil
still, if the armature current is reversed.
To explain the operation of this it may be considered when used as the only
means of field regulation without the variably shunted field coil.
With given initial and armature potentials, number of turns, etcetera, there will
be a direct magnetic effect due to the regular or sectional field coils which may be
expressed by the ampères flowing in such coils multiplied by the number of turns,
and there will be a negative effect produced by the armature field coils which may
be expressed by the ampères flowing through the armature, multiplied by the
number of turns in the said coils. This gives a differential field which may be
expressed by the difference in number of ampère-turns of these two factors.
Suppose the load upon the armature, under which it is running at some particular
speed to be diminished. The armature will increase its speed slightly, the counter
electro-motive force will be increased and the current flowing in the armature and
in its field coil will be diminished. This however immediately decreases the
negative effect of the differential coil, and the positive or direct field becomes more
predominant, the field is strengthened, and the counter electro-motive force is
increased, which further diminishes the armature current and the negative effect of
the field coil,-and so on. That is, the regulating influence thus employed to
govern the motor and prevent its racing, is cumulative, being set in action by a
slight increase in speed, and augmented by an increased field due to the
diminished influence of the differential coil whose influence depends upon the
armature current. Oppositely a slight decrease in speed causing a diminished
counter electro-motive force increases the effect of the differential coil and
diminishes the field.
With the motor running free, this coil will become practically dead and its
influence.nothing, but it is ready to automatically come into action the instant any.
load is placed on the motor.

page_text: It will be seen that with a motor running at a high efficiency, the change in
speed, provided the mass of iron in the core is sufficiently quick in changing its
magnetic state with a change in current, need be very slight.
The differential coil may however be placed outside the terminals of the
armature and main field shunts. In this case it is of course still in series with the
armature.
A Motor so arranged is preferably used on a circuit of constant difference of
potential, because in a circuit of constant current the motor must work at less than
50 per cent armature efficiency, which is uneconomical and therefore commercially
impractical.
On the two kinds of circuits the action of the motor is totally different. On a
constant potential circuit the drop in the potential between the line terminal and
the terminals of the armature and main field shunts-where the series coil is
situated varies with the load on the motor and the differential effect of the said
series coil therefore varies with the load; while in the constant current circuit, the
current in the series coil, so situated, is constant and so its differential effect is not
varied and the motor will not regulate except as stated when working at less than
50 per cent efficiency.
But the differential coil can be used as the sole means of regulation, only in
motors constructed for particular work and speed, for the two sets of coils must be
properly proportioned in constructing the machine to enable them to produce all
the different effects from the maximum to the minimum of field strength which
must be obtained in practice.
According to this part of the present invention, therefore, in order to apply the
principle to a general system of regulation of power and speed of a motor to meet
the various conditions which occur in practice both mechanical and electrical, my
said foreign correspondent combines the differential coil with the independent coils
shunted around more or less of the sectional coils as herein before explained.
Preferably also means are used for varying the armature current.
Having these methods of field regulation combined, the field can be adjusted by
means of the shunted coil to the particular work which the motor has to do at any
time; the series field coil will then act while the motor is running to regulate for
any changes which occur.
As has been suggested, the magnetic effect of the field coils on the cores may be
expressed by "ampère-turns." For a certain range of variation, the magnetic field
will be proportional to the ampère-turns, but this law will not hold when the iron
approaches saturation. Consequently a given ratio of increase of ampère turns
will not always give the same ratio of increase in counter electro motive force for
all given initial speeds; and more particularly will not a given numerical increase
of ampère-turns give the same ratio of increase in counter electro-motive force at
different speeds. Also the ratio of increase of counter electro-motive force from
maximum to minimum load depends upon the determined ratio with the initial
electro-motive force of which the counter-electro-motive force shall for the time bo
considered the normal, which, other conditions being equal, depends on the load.
As has been shown above, the use of an independent differential field coil gives the
ability to use any desired number of effective ampère-turns for the field.
Hence if a differential coil in the armature circuit is used it is best to have means
for varying its influence.
This may be done by cutting out more or less of the turns, or by throwing more
or less of them into parallel circuit with each other.
My said foreign correspondent however prefers to divide them into two sets, one
being sectional and the other having its terminals adjustable upon the sections,
precisely as herein before described for the main field coils.
By the foregoing arrangements and combinations, the most absolute and positive
control of an electric motor as regards speed and power is secured, either in hand &
or automatic regulation, up to the mechanical limit of its construction, and the
electrical capacity of the circuit,
01

page_text: For the complete regulation of a motor, however, one more element is required,
viz: the automatic adjustment of the commutator brushes to the non-sparking
points of the commutator cylinder; a portion of the invention consists in the
providing of means for this purpose.
Many different methods have been proposed for shifting automatically the
brushes of a dynamo electric generator for different purposes; no one of these
however is adapted for use with an electro-dynamic motor.
One proposed method is to keep the brushes at such points as will give a
constant potential with a varying load, as in some incandescent electric light
circuits. This does not keep them at the non-sparking points. Another is to
differentiate the action of three or more armature coils to maintain a constant
current. This does not prevent sparking. A. third proposes the use of one or
more accessory brushes and regulating apparatus in the circuit between the
accessory and the main collecting brushes. Such apparatus would equate the
potentials at the main and the accessory brushes and would not keep either at
the true non-sparking point.
Another method makes the movement of the brushes depend upon the armature
current to give a positive lead in the direction of rotation. In this connection the
marked difference may be pointed out between the action of generators as
ordinarily wound with continuous armature windings of the Paccinotti or Alteneck
system, and motors similarly wound, and such as will be used in practice.
Dynamos may be generally classed as series or shunt machines. In both, if the
speed is increased with a fixed external resistance, the field and the electro-motive
force are both increased and the brushes must be given an increased lead in the
direction of rotation In a machine for incandescent lighting, generally excited on
the shunt system, a decrease of external resistance is attended with an increase of
current and a lead is given to the brushes in the direction of rotation.
All methods of automatic regulation of brushes on this principle with which my
said foreign correspondent is acquainted depend for the positive movement upon
the current in the armature which is the total current in the circuit.
Two distinct influences, however, determine the proper position for the brushes
and these influences are differential.
With any given field the displacement is fairly proportional to the current in the
armature.
With a given armature current and displacement, if the strength of field is
increased, the displacement is diminished.
Now in a dynamo, the variations in the strength of the armature current and of
the field are of the same character, both being increased or both being diminished
by the same causes, though not necessarily in the same ratio.
In a motor designed to run at any given speed with varying loads, and regulated
in any way by the field, the armature current and the strength of the field must
vary inversely and whatever the lead given to the brushes, it is a negative one.
A further distinction between generators and motors is that in the generator the
direction of the current in the field is opposed to that in the armature; in the
armature, the current flowing toward what is ordinarily termed the positive brush,
and in the field, away from it, while if the machine is used as a motor to run in
the same direction the direction of the current in the field may remain the same,
while that in the armature is reversed, which of course reverses the polarity of the
armature.
In the dynamo, the field is properly a part of the external circuit and after
polarization there can be no reversal of a self-excited dynamo except by a reversal
of the direction of rotation, and shifting of the field terminals, and such reversal of
direction would reverse the lead of the brushes and shift the non-sparking point to
the opposite side of the middle position.
In a motor with shunt or series field, the polarity of the terminals of the machine
can be reversed as rapidly as desired without changing the direction of rotation or
the lead of the brushes.

page_text: If a dynamo with an electro-magnetic device for shifting the brushes be used as
a motor to run in the same direction, the action of the shifting device will cause
the brushes to spark badly and the entire reversal of its action would be necessary.
From the above it will be seen that no method which has been used of shifting
the brushes of a dynamo to the non-sparking point can be employed for the same
purpose with an electro-dynamic motor.
In motors in which the field magnet is not regulated, the brushes may be
regulated by the variations in armature current alone, an electro-magnetic device
being placed in the armature circuit and connected with the brushes so that an
increase of armature current causes the shifting of the brushes to increase their
negative lead.
But in a motor in which the field magnet strength is varied to change the speed,
it is necessary to also cause this variation of the field to affect the brushes so that
an increase in field strength acts oppositely to an increased armature current that
is it diminishes the negative lead of the brushes. For, as the magnetic field is due
both to the armature and the field magnet strength, a variation in either of these
factors causes a change of the non-sparking point and necessitates the shifting of
the brushes.
The method of regulation for the brushes which forms part of this invention,
consists, then, in automatically increasing the negative lead of the brushes simul-
taneously with an increase of the armature current (and vice versa) and decreasing
automatically the negative lead simultaneously with an increase of field magnet
strength (and vice versa).
In practice, for motors in which the field is varied, my said foreign corre-
spondent prefers to employ as a brush shifter an electro-magnetic device in which
armature and field magnet currents oppose each other, so that an increased armature
current and a decreased field current have the same effect on the brushes.
My said foreign correspondent has devised several different brush-shifting devices
acting on these principles.
In some of these the electro magnetic brush-shifting device is included in the
armature circuit and in the main field circuit; in others, in the armature and
independent field coil circuits, and in others in all three of these circuits. And in
one apparatus, the armature current is made to act in two directions on the
brushes, so that the effect is the same no matter in which way the current is sent
through the motor.
It is to be understood, that it is not necessarily for an increase in field current
but for an increase in field magnet strength that the negative lead of the brushes
is diminished.
An extended portion of the field magnet may be used in some cases to oppose
the electro-magnetism established by the armature current.
And in order that the said Invention may be perfectly understood, I shall now
proceed more particularly to describe the same and for that purpose shall refer to
the several figures on the accompanying sheets of drawings the same letters of
reference indicating corresponding parts in all the corresponding figures.
Figures 1, 2 and 3 are diagrams illustrating the simple principle of changing the
current in a shunt by moving its terminals upon the conductor from which it is
shunted.
Figure 4 is a diagram illustrating the independent field coil variably shunted
around the sectional coils.
Figure 5, illustrates the independent coil shunted upon a range of sectional coils
and the armature upon a continuous field coil.
Figure 6 shows two sectional ranges with the independent coil variably shunted
on one, and the armature variably shunted between the two.
Figure 7 shows both the armature and the independent coil variably shunted
between the two sectional ranges.
Figure 8 illustrates the variably shunted armature and independent coil and the
differential coil in series with the armature,

page_text: Figure 9, illustrates the same with the terminals of the independent shunted
coil reversed to give a differential action.
Figure 10 is the same as Figure 8 with the series field coil provided with a
variably shunted coil for varying its effect.
Figure 11 is the same with the variably shunted coils reversed.
Figure 12 shows the differential coil in series with the armature outside the
terminals of the armature shunt.
Figure 13 represents a motor having its armature and independent field coil
variably shunted upon the sectional field by the same commutator.
Figure 14 represents the same provided also with a field coil in series with the
armature.
Figure 15 the same, the said series field coil having a shunted coil and a
commutator for varying its effect.
Figure 16 shows an automatic device whereby changes in the armature current
may be made to change the position of the terminals of the variably shunted field
coil.
Figures 17, 18, 19, 20, 21 and 22 illustrate various automatic brush-shifting
mechanisms and
Figure 23 is a view of the motor provided with all the various regulating devices
described, with another brush shifting device.
In figure 1, A represents any suitable source of electric energy from which one
or more motors, or a system of motors, lamps, or other translating devices are
supplied. OC¹ are main conductors.
A derived circuit from the main is represented by a a¹, and b b is a shunt
therefrom. In figure 2, shunt b b¹ is taken directly from main C. It is evident
that by moving the terminals b, 61, toward or away from each other the current
in the shunt may be changed, and on such terminals passing one another the
current will be reversed.
In figure 3 the shunt b 6¹ is between two cross circuits a a³ a¹ and a a³ a¹ If
bb has the dotted position a a¹ its maximum current will flow. If it is brought
to position b b¹, the current is diminished and when at a³, as, no current will flow.
Beyond this position the current is reversed and continues to increase, the
maximum reversed current flowing at a¹ a.
In figure 4, let a a¹ represent a motor field circuit including sectionally wound
coils; cc' is the armature shunt and b b' is an independent field coil with movable
terininals. As shown in full lines, this coil assists the main field coils. The
dotted lines represent it reversed, and acting as a differential coil.
In figure 5 the armature shunt c c is upon one range of field coils and the
independent field upon another.
In figure 6 the armature shunt co¹ is between two sectional ranges of the field,
the arrangement being that illustrated in figure 3. The independent field is
shunted upon one range.
In figure 7 both the armature and independent field are shunted between two
sectional ranges.
In figure 8 B, B, are sections of main field coils; D is an independent series of
field coils variably shunted upon the sections; E is the armature also in a variable
shunt; and F is an oppositely wound field coil in series with the armature. In
this figure coils B and D act in the same direction and are opposed by coil F,
whose effect varies with the armature current, as has been already explained.
In figure 9, the terminals of coils D have been reversed and such coils oppose
the main coils. A portion of the differential coil F is cut out of circuit to change
its action, the motor being thus set for a different standard or normal speed.
In figure 10, the differential coil F is wound in sections and a coil F is shunted
upon it with movable terminals, so that its influence can be increased or diminished.
or reversed to change the effect of the differential coil.
: Figure 11 shows the coil F1 reversed as well as coil D.

page_text: In figure 12, the differential coil F, F¹ is placed in the direct motor circuit
instead of within the armature shunt. It is still, however, in series with the
armature. The effect has been already explained.
In figure 13, G is a circular cominutator having contacts e, e², e³, e³, ct.
Connections from the two ranges of sectional main field coils B, B, of the motor,
are made to these blocks in the following manner; the first connection or one
nearest main C is joined to one block e and the last one is connected to the
opposite block e¹; the second connection fis joined to two blocks e³, es, on either
side of e; likewise the connection f¹ next to the last connection is joined to two
blocks e³, e; the third connection to two blocks e, et; and so on until the blocks
meet on either side.
The commutator has two pairs of contact arms g, g³, and h, h'. The armature
terminals are connected to arms g, g¹, and the terminals of the independent field.
coils D to arms h, h. The rotation of a pair of these arms shunts the circuit with
which they are connected around a greater or less number of coils B, or reverses
such circuit. Thus the current in the armature, or the strength of the field is
regulated as herein before explained.
In figure 14, the differential field coil F is shown in series with the armaturo,
the figure being otherwise the same as figure 13.
:
In figure 15 the differential coil has means for regulating its effect. An extra
coil F is used the coils F being wound sectionally and the sections connected to
commutator H in the manner described with reference to figure 13. The contact
arms k, k, are connected with coil F¹ and by moving such arms the current in the.
said coil may be varied or reversed so as to make it a differential coil.
Figure 16 illustrates an automatic device for varying the field. A solenoid I
placed in the armature circuit has a movable core J which has any suitable
mechanical connection (not shown) with the terminal arms of the adjustable
independent field coil, so that such terminals are moved by variations in the
armature current. The core is provided with two adjustable stops 1, 1, and with an
adjustable retracting spring m. When the motor is placed in circuit for certain
work, the spring and stops are adjusted for the current used and the desired.
normal speed. An increase in the speed of the motor gives an increased counter
electro-motive force, causing a decrease in the armature current, and allows the
spring m to act, and the core moves the independent field coil terminals so as to
strengthen the field and reduce the speed again. This makes a cumulative action, 3
as the increased field again increases the counter electro-motive force. Thus & very
slight increase of speed acts upon the field as in the case of the differential coil in
series with the armature.
Figure 17 represents an automatic brush-shifting apparatus. Brushes n, n, are
carried by a pivotted arm L. A semi-circular arm N of magnetic metal is con- 4
nected with both ends of arm L and forms the movable core of two hollow electro-
magnets or solenoids O and O¹. The coils of magnet or solenoid O are in the
armature circuit 1, 2, of the motor, and the magnet O¹ has two sets of coils,-one
set in the circuit 3, 4 of the independent variable field coils the other set in the
circuit 5, 6 of the main field coils. If the armature current increases, the magnet O 4
moves the brushes against the influence of both coils of magnet O¹ so as to increase
the negative lead of the brushes. If the field strength is increased by increasing
the current in the independent field coil circuit 3, 4, the coil of magnet O' in that
circuit moves the brushes in the opposite direction so as to decrease their negative
lead. Or, if the current in the independent coil is decreased, the magnet O¹ 5
permits the brushes to increase their negative lead, and if the current of the
independent coils is finally reversed and the current then strengthened in these
coils, the main field coil circuit acts upon the brushes to still maintain the negative
lead.
In a motor in which the independent variable field coil is not used as a means 5
of regulation, but which has a simple field circuit provided with an adjustable

page_text: resistance or other current regulating device, the brush adjustment is performed by
the armature current and this main field-current only.
From this it will be evident that this method of brush adjustment is applicable
to all electro-dynamic motors.
It is to be understood that it is not necessarily for an increase in field current
but for an increase in field magnet strength that the negative lead of the brushes
is diminished.
An extended portion of the field magnet may be used in some cases to oppose
the electro-magnetism established by the armature current.
Figure 18 shows a single magnet or solenoid R controlling the curved core N
which ends at a¹, the part N¹ being of non-magnetic material. The solenoid has
three sets of coils. Coil 1, 2, is in the armature circuit; 3, 4, is in the independent
field circuit; and 5, 6, is in the main field circuit. The influence of coil 3, 4 is
changed as its terminals are changed to regulate the field and it opposes either the
armature or the main field current as the case may be.
Figure 19 is an arrangement similar in principle. The differential magnet or
solenoid R in which coils 1, 2 and 5, 6, oppose each other acts on one end of the
brush-holding arm while a spring S acts on the other. The independent field
coil 3, 4, opposes either the coil 1, 2, or 5, 6, and moves the brushes in one direction
or the other.
•
In figure 20 adjustable springs T, T, tend to hold the brush arm centrally. The
coil 1, 2, in the armature circuit acts on one end of the arm, while coil 3, 4, in the
inain field circuit opposes it at the other end. Coil 5, 6 of the independent field
circuit includes both magnets and acts in one way or the other according to the
position of its terminals. This device would be operative to a certain extent
without the springs T, T.
In figure 21, U is a sectionally wound solenoid, the position of whose core is
determined by the sections in circuit and the said core is attached to one end of
the brush arm L. The solenoid is energized preferably by a circuit 7, 8, separate
from the motor circuit. V is another magnet or solenoid having a movable core
which carries contacts, 9, 10. The magnet V is energized by opposing armature
and field currents and as its core moves up or down it places different sections of
solenoid U in circuit and so changes the position of the brushes.
In figure 22, W is the armature of a small electro dynamic motor. Upon its
shaft is a worm a meshing with a worm-wheel upon the pivot of the brush
arm L of the regulated motor. An insulating block w¹ carrying contacts p, p, is
so placed as to be moved up or down by the worm . The movable core of the
magnet carries contacts o, o, o. Magnet V is included differentially in the
armature and field circuits. When its core is pulled down, circuit is closed to
armature W in such a direction as to move the worm so as to give the proper lead
to the brushes, and to move block w¹ so as to again break the motor circuit. If
more movement is necessary, the current will of course cause the contacts o to
follow contacts p down and maintain the circuit the proper length of time. The
upward movement of the core closes circuit to motor W in the opposite direction
causing an opposite movement of all the parts.
The brush shifting apparatus shown in figure 23 operates equally well no matter
in which direction the current is sent through the motor.
The centrally pivoted arm L carries the commutator brushes n, n, which bear on
the commutator K. Upon the arm L is a polarized armature Y situated between
two curved pole magnets Z, Z, the coils of both of which are in the motor armature
circuit. When the armature current is in one direction, armature Y moves toward
Z and when in the other direction toward Z¹. An arm extends below the
armature Y and carries the core 8 upon which are wound the coils t¹t included, one
set (t¹) in circuit of the main or sectional field coils B, the other (t) in the circuit
of the independent variably shunted field coils D. These field circuit coils t¹, t,
tend to hold the polarized armature Y centrally, but armature circuit coils Z and Z¹
tend to move it in one direction or the other. (The coil t will be omitted in a

page_text: motor having a simple field circuit provided with a current regulating device and
then the position of the brushes depends upon variations in the main field strength
and in the armature current).
If the field is strengthened, the coil in the main field circuit acts to diminish
the negative lead of the brushes for the increased counter electro-motive force and
¡decreased speed occasioned by the strengthening of the field, and a diminution of
the armature current has a like effect upon the brushes, for the coil t¹ opposes
,either the coil Z or Z¹.
The influence of coilt in the independent field coil circuit is changed as its
terminals are changed to regulate the field, and it opposes the influence either of
the armature or the main field current as the case may be.
This apparatus acts the same no matter in which direction the current is sent
through the motor, the lead given to the brushes being in the right direction in
whichever direction the current may be.
In this figure, the different parts of the current regulating apparatus are shown
separated and in diagram and the commutator of the motor is for clearness
separated from the armature and field magnet.
By means of commutator G¹, the connections to which are made in the manner
already explained, the armature is shunted upon a greater or less number of main
field coils B.
By commutator G³, the independent field coils D are variably shunted around
coils B.
It has been already shewn that both these operations may be performed by the
same commutator.
By commutator H, extra coil F¹ is shunted upon more or less of the differential
coil which is in series with the armature.
Automatic devices are shown for operating the arms on the commutators G¹
or G³
For commutator G¹ is shown a small electric motor u¹ of which u is the armature.
A centrifugal governor v, upon or connected with the shaft of the regulated motor,
closes circuit, by its movements, to motor u' in one direction or the other
according to variations in speed, and the armature u being connected in any
suitable manner with the pivoted arms on commutator G¹ moves the same in the
proper direction.
For commutator G2 is shown a polarized armature w centrally pivotted between
the curved pole pieces of magnets x, x¹. By means of centrifugal governor v
operated as just explained, circuit is closed through or ¹ and the pivotted
armature is drawn one way or the other. It is suitably connected with the
commutator arms and draws them in one way or the other to shift the terminals of
the independent field coil.
These automatic devices are shown for illustration merely, it being evident that
many other similar arrangements may be readily employed and that two similar or
different automatic devices may be employed to shift the armature and independent
field terminals when they are on the same commutator.
Having now particularly described and ascertained the nature of my said
Invention and in what manner the same is to be performed I declare that what
I claim is
1st An electric motor or generator having main field magnet coils, and other field
magnet coils independent of the armature circuit and variably shunted upon the
said main field coils, whereby the magnetizing effect of the said independent coils &
is varied, or varied and reversed.
2nd An electric motor or generator having main field magnet coils, the armature
in a circuit variably shunted upon the said main field magnet coils, and other
field magnet coils independent of the armature circuit, also variably shunted upon
the said main field magnet coils, whereby the difference of potential at the armature

page_text: circuit terminals and the magnetizing effect of the said independent field magnet
coils are varied, or varied and reversed.
3rd The arrangements of regulating apparatus for electric motors, substantially
as hereinbefore described with reference to Figures 8, 9, 10, 11, 12, 14 and 15 of
the accompanying drawings.
4th An electro dynamic motor, either simple or differential, having a device for
automatically maintaining its commutator brushes at the points of least spark, the
said device acting simultaneously with variations in the armature current, or
simultaneously with variations in the strength of the field magnet, or differentially
according to variations in both.
5th The brush adjusting apparatus shown in figure 23 and particularly described
with reference to that figure.
6th An electro-magnetic apparatus for maintaining the commutator brushes of
an electro-dynamic motor at the points of least spark, included in the armature
circuit alone, or in the armature and main field circuits or in the armature and
independent field coils circuits, or in all three of the circuits mentioned.
Dated this 18th day of December 1883
THS J. HANDFORD.