IMPROVED MEANS OF REGULATING; ELECTRIC CURRENTS AND ELECTROMOTIVE FORCE AND APPARATUS THEREFOR PROVISIONAL
Year: 1882

page_text: LETTERS PATENT to Louis Campbell, of Glasgow in the County of Lanark,
North Britain for an Invention of "IMPROVED MEANS OF REGULATING;
ELECTRIC CURRENTS AND ELECTROMOTIVE FORCE AND APPARATUS THEREFOR
PROVISIONAL SPECIFICATION left by the said Louis Campbell at the
Office of the Commissioners of Patents on the 21st October 1882.
LOUIS CAMPBELL, of Glasgow, in the County of Lanark, North Britain,
"IMPROVED MEANS OF REGULATING ELECTRIC CURRENTS AND ELECTRO-MOTIVE
FORCE, AND APPARATUS THEREFOR,"
In a dynamo or magneto-electric machine, the contact pieces of the commutator
are not all at the same electrical potential, and in practice the brushes or collectors
of these machines are placed so as to make contact with the commutator at the
points of highest and lowest potential. As the current and electro-motive force in
a conductor, are both proportional to the difference of the electrical potentials at
its ends, it is evident that if one or both of the brushes of these machines be
shifted so as to make contact with the commutator at any other point or' points,
there will be a corresponding change in the effects produced by these machines.
In my Invention this principle is made use of by having one or more of the brushes
movable or adjustable to any part of the commutator, automatically or otherwise.
In this case one of
The simplest example is, when only two brushes are used.
the brushes is most conveniently arranged so as to make contact with the
commutator at one of the points of extreme potential and the other adjustable,
automatically or otherwise, to any part of the commutator.
•
When there are two or more circuits, each requiring to be separately regulated,
they may each have their own set of independent brushes arranged as above
described on the one commutator, or the similar ends (say the positive ends)
of two or more of the circuits may be connected to one brush, and each of the
other ends of the circuits have an independent adjustable brush of its own.
In a dynamo, I produce the magnetism of the field magnets by having one or
more of these circuits circulating round them. When the contact pieces of the
.
+

page_text: commutator are few, more delicate regulation is obtained by introducing resistances,
and in dynamos, a portion of the field magnet coils may be short circuited, or cut
out of circuit.
The automatic adjustment may be accomplished by means of an electro-motor
connected to the brushes by gearing or screws. The motor is made to move the
brushes so as to produce more or less intense effects by a current which is passed
through the motor in one direction or the other by a relay which is actuated by
the current being regulated, or by the current which passes through a high
resistance conductor connecting the points between which the electro-motive force
is being regulated, or the brushes may be made, by means of weights or springs,
to have a tendency to assume on the commutator the position for maximum effect
that the machine can produce. The brushes are also connected by means of
gearing or screws to a motor which works in opposition to the weights or springs.
When the current or electro-motive force is too great, an electro-magnet (which is
actuated by the current being regulated, or by the current which passes through a
high resistance conductor connecting the points between which the electro-motive
force is being regulated) attracts an armature which causes a current to pass
through the motor and thus shift the brushes, and which, as long as the current or
electro-motive force is not less than the desired strength is prevented from
assuming positions for more intense effects, by means of a detent or break. The
preceding is more especially applicable to circumstances where it is inconvenient
to use dynamo machines relatively large for the demands made upon them. The
above is also applicable to the regulation of the speed of electro-motors. I prefer
the following when at all applicable.
to use.
The total electro-motive force produced in dynamo machines by the motion of
the machine consists of two parts. One of these parts is due to the residual
magnetism of the machine; and is augmented or diminished by terrestrial
magnetism according to the position of the machine; therefore the electro-motive
force due to the residual magnetism is practically constant for a constant speed of
the machine. The other part is due to the magnetizing influence of the current or
currents in the field magnet coils of the machine.
When in the regulation of electro currents, and of electro-motive force, a
constant source of electro-motive force has been required, hitherto magneto
machines, galvanic batteries, or even dynamo machines (in a circuit independent
of the main circuit) have been employed besides the dynamo-machine but in my
Invention I use the residual magnetism of the machine (augmented or. diminished
by terrestrial magnetism) as the prime source or base for the production of a
constant electro-motive force, instead of introducing magneto machines, batteries,
or a dynamo, as at present employed.
When the consumers resistances are in parallel or multiple arc, and it is desired
to maintain a constant electro-motive force between the consumers supply and
return conductors, I use an ordinary series dynamo machine arranged thus. The
dynamo machine is run at the constant speed which produces in the machine, when
the armature is disconnected from the field magnet coils, an electro-motive force
equal to the electro-motive force which it is desired to maintain between the
consumers supply and return conductors. Or in other words, the speed at which
the dynamo machine must be run, is such that the portion of the electro-motive
force produced in the dynamo due to the residual magnetism of the machine is
equal to the electro-motive force which is required to be maintained between the
consumers supply and return conductors; And the number of turns or con-
volutions in the coils of the field magnets ought to be such, that when the dynamo
machine runs at the above constant speed, the portion of the electro-motive force
produced in the machine due to the influence of the current flowing or circulating
in the field magnet coils, ought to be numerically equal to R C, where R is the
total constant resistance of the circuit, and C is the current circulating in the
circuit. This arrangement would sometimes necessitate the dynamo machine being
run at an inconveniently high speed. To obviate this inconvenience I wind a

page_text: second independent coil round the field magnets of the dynamo machine arranged
as just described, the ends of this second coil of the field magnets being connected
to the consumers supply and return conductors, and as the electro-motive force
between these conductors is constant, the current flowing through this second coil
is also constant, and gives rise to an additional constant electro-motive force in the
machine.
The magnitude of this additional constant electro-motive force depends on the
number of convolutions and resistance of the second coil.
The sum of this additional electro-motive force and the electro-motive force due
to the residual magnetism ought to be equal to the electro-motive force which it is
desired to maintain between the consumers supply and return conductors. The
electro-motive force which is due to the influence of the principal or total current
flowing through the other or first field magnet coil, ought to be numerically equal
to R. C, where R is the total constant resistance of the circuit (the resistance of the
second coil round the field magnet is not here included) and C is the principal or
main current flowing through the first coil round the field magnet.
When the consumers resistances are in series, and it is required to maintain a
constant current through them, I use an ordinary shunt dynamo-machine having
the convolutions and resistance of its field magnet coils, such that the electro-motive'
force due to the current circulating in the field magnet coils is numerically equal
to R C, where R is the sun of the resistances of the armature and field magnet'
coils, and C is the current circulating in the field magnet coils. The current in the
outer circuit equals the electro-motive force due to the residual magnetism of the
machine divided by the resistance of the armature of the machine. When
the current produced or circulating in the outer circuit by this arrangement is not
sufficiently strong, I wind additional coils round the field magnets. These
additional coils are in series with the outer circuit, and have therefore the constant
current, flowing through the outer circuit, circulating in them. The strength of
the current in the outer circuit is the greater, the greater the number of con-
volutions in the additional coils which are in series with the outer circuit.
The particular methods given for winding the dynamo machines in the particular
cases considered are the best methods adaptable to the particular circumstances, but
generally speaking, any of the methods for winding the dynamo machines may be
used to maintain either a constant electro-motive force (the consumers resistances
being in multiple are) between the consumers supply and return conductors, or to
maintain a constant current through the consumers resistances which are in series.
It is of course necessary that the number of convolutions and resistance of the field.
magnet coils as well as the speed of the machine be properly adjusted.
To make the one dynamo machine applicable to the maintainance either of a
constant electro-motive force between the consumers supply and return conductors,
or a constant current through the consumers resistances, I wind the coils of the
field magnets in such a manner that their various portions may be put in series
or divided circuit with each other; and when arranged in either of these ways,
they may be put either in series or in divided circuit with the outer circuit,
or so that some of the convolutions can be put in series with the outer circuit,
and the rest in shunt or divided circuit with the outer circuit, or in divided or
parallel circuit with the consumers resistances. In all these, portions of the
field magnet coils may be arranged to have no current circulating in them,"
or be short circuited, and resistances may be introduced if necessary. Or in
other words, the arrangement of the field magnet coils must be such that the
various portions of which they are composed can be connected or disconnected in
any manner whatever with each other, and with the different parts of the machine,
resistances, and conductors composing the system.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Louis Campbell in the Great Seal Patent Office on the 14th April
1883.
LOUIS CAMPBELL, of Glasgow, in the County of Lanark, North Britain,
"IMPROVED MEANS OF REGULATING ELECTRIC CURRENTS AND ELECTRO-MOTIVE
FORCE, AND APPARATUS THEREFOR
"
My said Invention relates to improved means of regulating electric currents and
electro-motive force in dynamo-machines.
The total electro motive force produced in a dynamo machine by the motion of
the machine is made up of two parts. One of these is practically constant and is
due principally to the residual magnetism of the machine, the other is variable,
and is due to the influence of the current circulating in the field magnet coils.
When it is desired to maintain a constant electro-motive force between the.
consumers supply and return conductors (the, consumers appliances being in
multiple arc) I use an ordinary series dynamo machine modified thus,—The dynamo
machine is run at the constant speed which produces in the machine (when there
is no current circulating in its field magnet coils) an electro-motive force equal to
the electro-motive force which it is desired to maintain between the consumers
supply and return conductors. Or in other words, the speed at which the machine
must be run is such that the portion of the electro-motive force produced in the
dynamo-machine due principally to its residual magnetism, is equal to the electro-
motive force which it is desired to maintain between the consumers supply and
return conductors.
The number of turns or convolutions of the field magnet coils ought to be such
that when the dynamo machine runs at the above constant speed, the portion of
the electro-motive force due to the influence of the current circulating in the field
magnet coils is equal to R C volts, when R is the numerical value of the total
resistance of the circuit in ohms and C the numerical value of the current in
amperes circulating in the field magnet coila.
The arrangement just described would sometimes necessitate the dynamo machine
being run at an inconveniently high speed. To obviate this inconvenience, I first
wind the dynamo machine similarly to an ordinary series dynamo-machine, and
run it at the constant speed at which it maintains a constant electro-motive force
between the consumers supply and return conductors, or the dynamo may be run
at any convenient constant speed, but having the number of the convolutions of
the field magnet coils such that, when run at this convenient constant speed, the
portion of the electro-motive force due to the influence of the current circulating in
the field magnet coils is equal to R C volts, R being the total constant resistance
of the circuit, and C the current circulating in the field magnet coils. At this
stage the dynamo would maintain a constant electro-motive force between the
consumers supply and return conductors, but the electro-motive force would be less
than that required. I now wind round the field magnets a second coil, the ends of
which terminate in the consumers supply and return conductors. As the electro-
motive force between these conductors is constant, so also is the current flowing
through this second field magnet coil, and this gives rise to an additional amount
of constant electro-motive force in the machine. The resistance and number of
convolutions of this second coil may be found from the following formula-.
Before winding, the second coil on the field magnets, close the circuit with a
resistance, and let the current circulating in the field magnet coils be C, and the
total electro-motive force produced be E, close the circuit with another resistance,

page_text: let c and e be the corresponding current and electro-motive force; if the constant
electro-motive force between the consumers supply and return conductors be e₁,
and the constant electro-motive force which it is desired to be maintained be E
n the number of convolutions of the field magnet coils, N the number of. convo-
lutions of the second field magnet coil, and M the resistance of this second field
magnet coil; then
E, N (E--e)
E₁ = (C—c) n
-
A more convenient method of accomplishing this object is to take a dynamo
wound as an ordinary shunt dynamo, and run it at the speed which produces at the
brushes when the outer circuit is open, an electro-motive force equal to the constant
electro-motive force which it is desired to maintain between the consumers supply
and return conductors, and then join one of the ends of the outer circuit to the
nth convolution of the field magnet coils, and the other end to the mith convolution
of the field magnet coils, or to one of the brushes, m and n being counted from the
same end of the field magnet coils, m must be greater than n and equals N (the
total number of convolutions of the field magnet coils) when one of the ends of the
outer circuit is terminated in one of the brushes m and n may be found thus,
Run the dynamo as an ordinary shunt dynamo, and at the above constant speed,
let E be the total electro-motive force in the machine, and C the current circulating
in the field magnet coils when the outer circuit is open, and e and c the corre-
sponding electro-motive force or current when the outer circuit is closed, A
the resistance of the 'armature from brush to brush, and R the resistance of
the (N+n-m) convolutions of the field magnet coils, we have N+n-m
(E-8)
N = A + R.
(0-c)
When it is desired to maintain a constant current through the consumers'
appliances which are in series, I use an ordinary sbunt dynamo machine modified
thus, The dynamo is run at the constant speed which produces in it (when there
is no current circulating in its field magnet coils) an electro-motive force of A C
volte where A and C are the armature's resistance in ohms from brush to brush,
and the constant current in amperes which is to be maintained through the outer
circuit; and the resistance and number of the convolutions of the field magnet
coils ought to be such that when the machine runs at the above constant speed,
the electro-motive force produced in the. machine due to the influence of the
current circulating in the field magnet coils is equal to (A+M) C, where A is the
resistance of the armature from brush to brush, M the resistance of the field
magnet coils, and C the current circulating in the field magnet coils. The above
is arrived at by first temporarily winding the field magnets with a conductor of
known resistance and number of convolutions, and from the results obtained the
resistance and convolutions of the permanent field magnet coils is calculated.
A more convenient method of maintaining a constant current through the con-
sumers appliances which are in series is to wind the dynamo as an ordinary shunt
dynamo and run it at the speed at which it will maintain a constant current in
the outer circuit, whatever the resistance of the outer circuit may be. Remove the
outer circuit from the brushes and join one of its ends to the nth convolution of the
field magnet coils, and the other to one of the brushes, or to the mth convolution of
the field magnet coils m and n being counted from the same end of the field
magnet coils, m must be greater than n and equals N (the total number of the
convolutions of the field magnet coils) when one of the ends of the outer circuit
terminates in one of the brushes. To calculate m and n proceed thus, -Run the
dynamo as an ordinary shunt dynamo, and at the above constant speed let E be
the total electro-motive force in the machine, and C the current circulating in the
field magnet coils when the outer circuit is open; and e and c the corresponding
electro-motive force and current when the outer circuit is closed, A the resistance
of the armature from brush to brush, C, the constant current it is desired to

page_text: we
have
maintain in the outer circuit, C, the constant current it can maintain in the outer
circuit when run as an ordinary shunt dynamo at the above speed, then
(E-e) (N+-) CA (C₁- α).
(C-c) N
Dynamo machines which are made for general service are best wound with their
field magnet coils in several sections, instead of being in one continuous conductor,
and the free ends of the various sections may be brought to any convenient
commutator or switch, or else connected to one another and to other appliances by
means of binding screws and conductors..
These modifications are applicable to all forms of dynamo machines for currents
in the one direction, and in dynamo machines having more than one field magnet
it is not necessary that each of the field magnets be excited by the principal and
branch currents, for some of them may be excited by the principal current only,
and the others by the branch currents only.
In the Provisional Specification of my Invention, I described a method of
regulation, by causing the brushes collecting the currents produced in dynamo
machines, to be automatically shifted on the commutator. I have since abandoned
this method of regulation and desire to make no claim to it nor to any means of
regulation which is not described in my final Specification; but what I do claim is,
the particular methods herein described of winding and running/dynamo machines
so as to render them self-regulating.
い
In Witness Whereof, I, the said Louis Campbell, have hereunto set my hand
seal this Thirteenth day of April, in the year of our Lord One thousand
eight hundred and eighty three.
Witness,
WR.M THOMSON
Patent Agent
Glasgow,
LOUIS CAMPBELL (L.S.).