IMPROVEMENTS IN DISTRIBUTING AND MEASURING ELECTRICITY AND IN APPARATUS TO BE EMPLOYED FOR THOSE PURPOSES.
Year: 1882

page_text: "
LETTERS PATENT to John Hopkinson of Westminster Chambers in the County
of Middlesex F.R.S. for an Invention of IMPROVEMENTS IN DISTRIBUTING
AND MEASURING ELECTRICITY AND IN APPARATUS TO BE EMPLOYED FOR
THOSE PURPOSES.
"
PROVISIONAL SPECIFICATION left by the said John Hopkinson at the
Office of the Commissioners of Patents on the 27th July 1882.
JOHN HOPKINSON of Westminster Chambers in the County of Middlesex F.R.S.
"IMPROVEMENTS IN DISTRIBUTING AND MEASURING ELECTRICITY AND IN APPA-
RATUS TO BE EMPLOYED FOR THOSE PURPOSES."
My Improvements principally relate to maintaining the Electro Motive force on
a system of Conductors for an electric supply at a fixed potential but they also
relate to reducing the cost of such conductors consistently with efficiency and
safety to arrangements for disconnecting the dynamo machines from the Conductors
and to Improvements in the Instruments for measuring the quantity of Electricity
sent into or drawn from the system of Conductors. When Electricity is delivered
by means of a pair of Conductors to a distance from the Station where the
Electricity is generated there is a fall of potential due to the resistance of such
Conductors greater as the current is greater and if it is desired to maintain the
potential constant at the delivery end it is necessary to increase the potential at
the supply end as the current increases in a suitable manner To ascertain the
potential at the far end of the Conductor I make use of a Galvanometer differentially
wound with two coils the one coil having a high resistance as for measuring
potential the other of very low resistance conveys the current to the main
Conductor and acts in opposition to the high resistance coil.
The differential coils may be wound on an Electro magnet which acts as a relay
to ring an electric bell or to set in motion or reverse a small dynamo Machine to
adjust resistances or control the speed of the Steam Engine for the purpose of
keeping the potential on Service main Conductors constant. An approximation to
the same end may be attained by winding on the electro magnets of the Dynamo
Machines in addition to the usual coils whether in shunt or conveying a current

page_text: from a separate centre a few coils conveying the current to the main conductor
the effect of such coils being suitably adjusted. These latter coils may be wound
on a separate Electro Magnet The above improvements are in part also applicable
when the resistance of the main Conductors is not so great as to cause any serious
fall of potential For the purpose of economizing the cost of main conductors I
place two dynamo-machines in series and place two systems of Lamps or other
appliances consuming Electricity of approximately equal capacity also in series.
A main conductor is taken from each extreme pole of the two dynamos and a
smaller conductor from between the two dynamos to points between the two
systems of Lamps. This intermediate Conductor serving to bring back to the
central station any electricity required for one system of lamps in excess of that
required for the other system of Lamps.-The wire casing used to protect the two
main Conductors may be used as intermediate Conductors-More than two dynamos
may be placed in series and more than one intermediate smaller conductor may be
used on the same principle as is above described-For commercial supply of
electricity meters are needed. I have introduced an improvement into that for which
Letters Patent were granted to me dated the fourth day of January 1882 N° 49
which consists in modifying the make and break of contact therein described in
such wise that if the surfaces making contact one rotates relatively to the other so
keeping the surfaces clean. In a large electrical supply it is necessary that many
Dynamo Electric Machines shall send electricity; it is also necessary at times to
switch out one or other of such machines, this causes destructive sparks at the
switch.
I obviate this evil in some cases by introducing a resistance in combination with
the Switch which resistance is in the form of an electrolytic cell or series of Cells
containing acidulated water or other suitable Electrolyte giving off gas-Another
mode of obviating the evil is to use a switch in which contact is maintained by an
Electro Magnet and which automatically breaks when the current approaches zero
from the slackening of speed.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said John Hopkinson in the Great Seal Patent Office on the 27th January
1883.
JOHN HOPKINSON of Westminster Chambers in the County of Middlesex F.R.S..
"IMPROVEMENTS
DISTRIBUTING AND MEASURING ELECTRICITY AND IN.
IN
APPARATUS TO BE EMPLOYED FOR THOSE PURPOSES
My Improvements principally relate to maintaining the electro motive force in a
system of conductors for an electric supply at a fixed potential but they also.
relate to reducing the cost of such conductors consistently with efficiency and
safety; to arrangements for disconnecting the dynamo machines from the con-
ductors; and to improvements in the instruments for measuring the quantity of
When electricity
Electricity sent into, or drawn from, the system of Conductors.
The
is delivered by means of a pair of conductors to a distance from the station where
the electricity is generated there is a fall of potential due to the resistance of such
Conductors greater as the current is greater and if it be desired to maintain the
potential constant at the delivery end it is necessary to increase the potential at.
To ascertain the
the supply end, as the current increases, in a suitable manner
potential at the far end of the conductor I make use of a Galvanometer,
differentially wound with two coils the one coil having a high resistance as for
measuring potential and the other coil, of very low resistance, conveys the current
to the main Conductor and acts in opposition to the high resistance coil.
differential coils may be wound on an electro magnet which acts as a relay to ring
an Electric bell or to set in motion or reverse a small dynamo machine to adjust
resistance or control the speed of the steam Engine for the purpose of keeping the
potential on service main Conductors constant. An approximation to the saine end,
may be attained by winding on the electro magnets of the dynamo machines in
addition to the usual coils, whether in shunt or conveying a current from a
separate exciter, a few coils conveying the current to the main conductor the effect
of such coils being suitably adjusted. These latter coils may be wound on a
separate electro magnet.
For the purpose of economising the cost of main conductors I place two dynamio
machines in series and I place two systems of Lamps or other appliances
A main.
consuming electricity of approximately equal capacity also in series.
conductor is taken from each extreme pole of the two Dynamo's and a smaller
conductor from between the two dynamos to points between the two systems of
Lamps this intermediate conductor serving to bring back to the central station any
electricity required for one system of lamps in excess of that required for the other.
system of Lamps. The iron casing used to protect the two main conductors may
be used as intermediate Conductors. More than two dynamos may be placed in
series and more than one intermediate smaller conductor may be used on the same
principle as is above described. For commercial supply of electricity meters are
needed and I have introduced an improvement into that for which Letters Patent
were granted to me dated the Fourth day of January in the year of Our Lord One
thousand eight hundred and eighty two N° 49 which consists in modifying the
make and break of contact therein described in such wise that of the surfaces
making contact one rotates relatively to the other so keeping the surfaces clean
In a large electricial supply it is necessary that many Dynamo electric machines
shall send electricity, it is also necessary at times to switch out one or other of
such machines this causes destructive sparks at the switch. I obviate this evil by.

page_text: using a switch in which contact is maintained by an Electro magnet which contact
automatically breaks when the current approaches zero from the slackening of
speed.
And in order that my said Invention may be fully understood I shall now
proceed more particularly to describe the same and for that purpose shall refer
to the several figures on the annexed sheets of drawings.
Many devices have been proposed and used for keeping the difference of
potential between the terminals of dynamo machines constant or for indicating.
when such potential deviates from its standard amount. When the electricity is
to be used at a distance from the dynamo and conductors of a sensible resistance
are used it is proper to maintain constant the difference of potential at the end of
such conductors where the electricity is used and not at the dynamo itself Ife be
the difference of potential of the poles of the dynamo r the resistance of the
conductors from the dynamo to the place where the electricity is to be used and c
the current, it is necessary to maintain not e constant but e-c which is equal to
the difference of potential of the two conductors at their other end.
This I attain by using a differential regulating or indicating apparatus as shewn
diagrammatically in figure 1. A is the Dynamo Machine B are the lamps all placed
near each other connecting the conductors but all remote from A. The indicating
apparatus is wound with a coil of thin wire making many convolutions. This Coil
is connected to the poles of the Dynamo Electric machine at E and F and is there-
fore a shunt to the circuit the indicating apparatus is also wound with a thick
coil through which the whole current may pass or a proportional part thereof from
G to H the direction of the current in the thick coil being opposite to that in the
thin coil as indicated by the arrows. I prefer to use a proportional part of the
current through the thick coil as it is then easy (by properly adjusting the
resistance) to secure that, for the particular value of which occurs, erc shall be
constant It is best to make the thin coil of German Silver as it is important that
its resistance shall not vary sensibly. This differential apparatus may take a great
variety of forms without departing from the essential feature of my Invention It
may also be arranged either to indicate directly to the eye when the value of e―rc
is incorrect or it may be used to operate as a relay and by making an electrical
contact may cause a bell to ring or it may operate to introduce resistance or take
resistance from one of the Dynamo circuits or it may be used to control the speed
of the engine by any suitable method which has been proposed or used for main-
taining the difference of potential constant between the poles of a Dynamo Machine.
Figure 2 shews how the differential instrument may be arranged to act as a relay.
A. B are the coils of thick wire and CD the coils of thin wire both wound on the
same cores the preponderating effect of the thin wire being opposed by the spring E
attached to the moveable armature G carrying the contact piece F which makes
contact with H or I according as erc is too great or too small and so closes the
circuit of one or other of two electric bells or of other apparatus for indicating or
regulating.
The application of this instrument to an extended system of electrical supply
with a network of distributing mains is important For each machine I provide a
pair of feeders of a size appropriate to the current they are to carry but indepen-
dent of the distance they have to go. Each pair of feeders goes to and is connected
to some part or other of the system of distributing mains and by the use of my
Invention I am able to keep the difference of potential constant at or near the
point where the feeders join the distributing mains. By using a sufficient number
of feeders I am able to keep the potential throughout the distributing mains very
nearly constant, however the distribution of the consumption may vary, without
requiring conductors of excessive size.
It is possible to keep ere approximately constant by the action of the
Dynamo itself and so to reduce the variations within manageable limits. The
electro magnets of the Dynamo are wound with a thin or shunt coil and also with
a thick coil to carry the whole current from the dynamo. The current in the two

page_text: coils circulating in the same direction and they may be adjusted in such wire that
e-rc is approximately constant. This adjustment may be effected by introducing
a suitable resistance into the shunt coil of the magnet or preferably by giving a
sufficient number of convolutions to the thick coils of the magnet and then
shunting them with a wire the resistance of which is made such that the desired
effect is attained. Suppose the main line gives 500 ampères maximum current the
shunt may be such that e-r c has the standard value for a given speed when the
current is 100 and when it is 400 it will then never deviate far from the standard.
The adjustment required may be accomplished by aid of graphical construction but
the experimental method is more practicable. If the value of e-r c be less for
400 ampères than for 100 it is necessary to cause more current to flow round the
magnets in the thick coil or to flow through a greater number of convolutions. If
the value of er c be greater for 400 ampères than for 100 it is necessary to cause
less current to flow round the magnets in the thick coil. Instead of using a thin
coil as a shunt to the machine for producing the main excitation a coil supplied
with electricity by a separate machine may be used the method of adjustment
being the same. Figures 3 and 4 show diagrammatically the connections of the
circuits in the two methods I have described. When special circuits are required
for specific purposes as for charging secondary batteries or for arc lighting in
addition to the ordinary incandescent lighting such special circuits may be pro-
vented from disturbing other circuits by an application of the method hereinbefore
described, that is to say, by providing on the electro magnet of the dynamo
machine a special coil for the current of special use and adjusting the current
through the coil or the number of convolutions in the coil in the manner herein-
before described so that making or breaking the special circuit does not disturb the
other circuits.
I make no distinct and separate claim for the doubly wound magnets above
described but have explained them here because they may be usefully employed
with a slight modification in combination with the conductors as arranged under the
next described head of my Invention and also in combination with the first described
head of my Invention.
On
In order to combine the advantages of comparatively high potential in the
feeding conductors with lower potential in the houses in which the electricity is
used. I make use of a system of three conductors in combination with two dynamo
machines coupled in series This system is shewn diagrammatically in Figure 5
where A. B. represents the two dynamos, C. D. and E F. represent the extreme con-
ductors which I will call the positive and negative conductors and G, H, represents
the intermediate conductor. The positive pole of the dynamo machine A is
connected to the conductor C. D. and its negative pole to the conductor G. H.
the other hand the positive pole of the dynamo machine B is connected to the
conductor GH and its negative pole to the conductor E. F. The houses to be
supplied are divided into two approximately equal parts preferably the houses
being taken alternately. The houses of one part are supplied between the con-
ductor C. D. and the conductor G. H. and those of the other part between the
conductor G. H. and the conductor E. F. The intermediate conductor G. H. may be
of much smaller dimensions than either of the other two as it has only to carry the
difference of current consumed by the two divisions of consumers that is those
connected with the conductor C. D. and those connected with the conductor E. F. It
need not be insulated and indeed it may be replaced by the iron or other metallic
covering often used to protect the copper conductors In cases where the two
divisions of consumers may be safely assumed to have a very approximately equal
consumption at all times the intermediate conductor G. H. may be replaced in part
by the earth and the negative pole of the dynamo machine A and the positive pole
of the dynamo machine B be connected together and to the earth.
This system may be extended by using more than two dynamos in series and
dividing the consumers into as many groups, there will then be two large conductors
connected to the extreme pole of the dynamos and a number of smaller intermediate

page_text: conductors one less than the number of machines each connected to the junction of
two machines of the series.
To apply the indicating or regulating apparatus of the herein before first described
head of my Invention to the system of conductors hereinbefore last described it is
necessary to wind a third coil to convey the current going or returning by the inter-
mediate conductor G. H. it is in fact necessary to maintain e-r₁ c₁―r₂ c₂ constant
when e is the difference of potential between the pole of the dynamo machine;
is the resistance of the conductor C, D, r, is the resistance of the conductor G, H,
and c c. are the currents in these conductors
In like manner to apply the approximate method above described to the system
of these conductors two main circuits coils are required on the dynamo machine but
the method of adjustment is the same as in the simple casc.
In the Specification to Letters Patent N° 49 granted to me as of the fourth day
of January in the year of Our Lord One thousand eight hundred and eighty two
are described certain forms of instruments or meters for registering the total current
which has passed In Figures 1 to 4 of that Specification is shewn a form of the
Apparatus in which an electric contact has frequently to be made and broken. This
arrangement is liable to the contingency that the contact may become dirty and
require attention. This objection is obviated by the arrangement shewn in figure 6
of the accompanying drawings. The piece A is carried by and revolves with that
part B of the core of the electro magnet H which is suspended from the governor
and it makes contact with the bar C which is insulated and does not revolve. Thus
there is always a rubbing when contact is made which serves to keep the two
surfaces clean. The insulated bar C is held up by the spring D.
The other parts of the meter are similar to and act as described in my said
Specification N° 49 in the Year of Our Lord One thousand eight hundred and
eighty two.
When more than one dynamo machine supplies electricity to a system of
distributing mains there is some difficulty in removing a machine from the circuit
without a destructive electric are being formed when the circuit is broken. This
inconvenience I remedy by introducing into the conductor from the dynamo
machine an instrument such as is shown in detail in figures 7 and S, which are
views at right angles to each other. A A, is an electro magnet in the circuit of
the dynamo machine, its armature B carrying a piece C making connection between
D and E in the circuit. The connection between D and E is maintained so long
as a certain current passes in the circuit but when the current diminishes to a
point below this limit the armature B and piece C drop and the contact between
D and E breaks. The position of this automatic switch in the circuit is shewn
in figure 9 where A, B, represent two dynamo machines and C, D, the switches
above described.
If it be desired to break the circuit of one of the dynamo machines, it is only
necessary to stop such machine and as its speed diminishes, at the right moment
its automatic switch piece drops and the connection ceases. The form of the
switch may of course be varied. Such switches are also of use in the following
case which occurs in distributing electricity: Suppose that two feeding conductors
going to different parts of the system of mains are suppled by one Dynamo
machine but that owing to more lights being connected in the evening it is desired
to remove one of the feeding conductors from that machine and connect it to
another. The method is as follows, let A and B, Figure 10, represent the positive
conductors from the two dynamo machines and C and D the two feeding con-
ductors and that it is desired to transfer D from A to B without disturbing the
supply. Connect A to D, through the automatic switch at E and remove all other
connection, bring the machine B to a potential a little in excess of A, connect
B to D by the automatic switch at F or even by a simple hand switch and the
contact piece of the switch E will at once drop without any are and the change
desired is effected.
The foregoing description of instruments relates more particularly to continuous

page_text: currents but it is obvious that the arrangements Figures 1, 2, 5, 9, and 10, are
also applicable to alternate currents but in that case the iron in the electro
magnetic apparatus must be so divided that local induced currents are prevented.
Having now described and particularly ascertained the nature of my said
Invention and the manner in which the same is or may be used or carried into
effect I would observe in conclusion that what I consider to be novel and original
and therefore claim as the Invention secured to me by the herein before in part
recited Letters Patent is :
First, The employment of a differentially wound indicating or regulating
apparatus so connected to the conducting wires from a generator of Electricity
to a distant place as to indicate when the difference of potential between the two
conductors leading to such distant place deviates froin an assigned value at that
distant place or to regulate the electricity, producing machinery in such wise as to
maintain a constant difference of potential at a distance from the place of supply
or generation of the current substantially as hereinbefore described with reference
to Figures 1 and 2 of the accompanying Drawings.
Second. In a system of electrical distribution or supply, the employment of three
(or more) conductors in combination with two (or more) Dynamo Machines in
series substantially as herein before described with reference to Figure 5 of the
accompanying Drawings whether the middle conductor be continuous or be replaced
by an earth return.
Third. The means for, or method of, removing a dynamo machine from connection
with the external circuit or of changing a circuit from one dynamo machine to
another by means of an automatic Electro magnetic Switch substantially as
herein before described with reference to figures 7, 8, 9 and 10 of the accompanying
Drawings.
Fourth, The improvements in the current meter described and claimed in the
Specification of my aforesaid Patent N° 49 in the Year of Our Lord One thousand
eight hundred and eighty two consisting in providing the meter with a rubbing
contact at the part where the circuit of the motor of the meter is broken sub-
stantially as and for the purpose hereinbefore described with reference to Figure 6
of the accompanying drawings.
In witness whereof I the said John Hopkinson have to this my Specification
set my hand and seal this twenty-seventh day of January One thousand
eight hundred and eighty three.
JOHN HOPKINSON
(LASO)

page_text: Designs, and Trade Marks Act, 1883. For Amended Specification see Star Number.
(Librarians are requested to attach this Slip to the printed copy of the above Specification.)