An Electro Dynamic Relay for Constant or Varying Currents.
Year: 1888

page_text: Date of Application, 8th May, 1888
Complete Specification Left, 7th Feb., 1889
Complete Specification Accepted, 23rd Mar., 1889
PROVISIONAL SPECIFICATION.
An Electro Dynamic Relay for Constant or Varying Currents.
WILLIAM EDWARD AYRTON, Fellow of the Royal Society Professor of Applied
Physics at the City and Guilds of London Central Institution Exhibition Road
London, JOHN PERRY, Fellow of the Royal Society, Doctor of Science, Professor of
Engineering at the City and Guilds of London Technical College Finsbury, and
DAVID COOK Electrical Engineer Glasgow, do hereby declare the nature of this
invention to be as follows:-
Our invention enables us to obtain a magnified, equal, or diminished image A of
another current B and consists of one or more coils or other configurations of wire
called through which passes the current B which is to be measured, or whose
variations are to be noted and one or more coils or other configurations of wire or
conducting material called a whose rapid motion relatively to generates the current A.
This latter, A, is the current to be actually observed on a galvanometer, or telegraphic
receiveing instrument or telephone or other apparatus the actuation of which by the
current B would have been desired for any purpose only that for some reason it is
inexpedient to allow B to actuate it.
For example B may be a feeble rapidly varying telephonic current too feeble to
actuate a receiveing telephone; in this case A is made to be a magnified image of B
so that A can properly actuate the telephone receiver. Again B may be the altering
feeble current received from a submarine cable too feeble to actuate ordinary
telegraphic instruments in this case again A is made to be a magnified image of B.
Again A may be a current in a straight wire b, say an ordinary telegraph wire, and
A the current obtained from coils a made to rapidly rotate in the neighbourhood of the
wire. Again B may be the varying current in a coil 6 in circuit with a microphone,
this circuit being necessarily of small resistance, and A the magnified or diminished
image of B may be produced in a circuit of any required resistance. Again B may
be a feeble telephone current and A may be a magnified image of B capable of
working a considerable number of telephones placed either in series or in parallel
with one another. Again B may be a current sent along a telegraph line, and A may
be a greatly magnified current working electric lamps, the light from the lamps
being automatically made to vary greatly in strength for signalling, or other purposes
by variations made in the weak current A sent along the telegraph line.

page_text: In all these cases a may be regarded as the gramme, disc, or drum armature of a
magneto or dynamo machine the current B being made to pass round the field
magnets and the image A obtained from the brushes rubbing on the commutator.
Both a and b may have iron parts like the iron of the armature & field magnets of a
dynamo, but when A is to be an exact image of B it is desirable to dispense with
any iron in either a or b. The use of iron enables a great magnification of B to be
produced with a sinall machine, but in many cases the use of iron prevents A being
an exact image of B, and hence the quantity of iron which we use is different in
machines designed for different purposes. In some cases, especially in telephone
work, it is desirable that the current A should be a very exact image of the
current B, and in. that case our armature a consists of a simple disc of conducting
metal the current being obtained from a brush rubbing its periphery and axle.
Again some parts of the system of coils a, called a¹ may be fixed relatively to b, the
rest being moveable, although the same current passes through both fixed and,moveable
parts. Any existing series dynamo whose external resistance is so great and the
amount of iron employed in its construction so small that the machine cannot excite
itself at the speed at which it is being driven, and which has in addition an auxiliary
coil b on the field magnets fed by an external current. B is an illustration of this
form of our invention, a¹ being the series field magnet coils through which the
current A passes and 6 the additional coil on the field magnet. Again some part of
the system of coils a, called all may be fixed relatively to b, the rest being moveable,
but the parts all are shunts to the other parts of a. Any existing shunt dynamo
which is not self-exciting and which has in addition an auxiliary coil b on its field
magnet fed by an external current. B is an illustration of this form of our invention.
Or again those parts of a which are fixed relatively to b may some of them be in
series with and some of them shunts to the moveable part of a. Any existing com-
pound wound dynamo which is not self exciting and which has in addition an
auxiliary coil 6 or its field magnet fed by an external current B is an illustration of
this form of our invention.
The position and volume of the coil or coils b relatively to the part of a which
moves relatively to 6 will depend upon the amount of energy which the relative
motion of the parts of our apparatus is to convert into electric energy. Thus if b's
energy is small and we wish a's to be large the volume of 6 is small compared with
the volumes of the fixed parts of a; and b is placed in a better position than the
fixed parts of a to produce the magnetic field in which tho moveable parts of a rotate,
care being taken however that the current A. produced in the moveable or in the fixed
parts of a does not materially affect the current B.
As our invention enables us to produce in a currents which represent, to another,
or to the same, scale currents in 6 however the latter may vary, we adopt the following
combination when a sufficient scale of change of current is not produced in one
operation The original current B₁ is made, in one or other of the ways already
described, to produce a current A; this current A, is used as the B, in a second
machine to produce a second current A, and so on; hence the final current A is the
image of the original current B₁ but on a greatly magnified or greatly diminished
scale.
Dated this Fourth day of May 1888

page_text: An Electro-dynamic Relay for Constant or Varying Currents.
WILLIAM EDWARD AYRTON Fellow of the Royal Society Professor of Physics at
the City & Guilds of London Central Institution Exhibition Road JOHN PERRY
Fellow of the Royal Society, Doctor of Science Professor of Mechanical Engineering
at the City & Guilds of London Technical College Finsbury and DAVID COOK
Electrical Engineer Glasgow, do hereby declare the nature of our said invention and in
what manner the same is to be performed, to be particularly described and ascer-
tained in and by the following statement :-
Our invention enables us to obtain a magnified equal or diminished image A of
another electric currrent B and consists of one or more coils or other configurations
of wire called b through which passes the current B which is to be measured or
whose variations are to be noted and one or more coils or other configuration of wire
or conducting material called a whose rapid motion relatively to generates the
current A. This latter A may be observed on a galvanometer or telegraphic
receiving instrument or telephone or other apparatus the actuation of which by the
current B would have been desired for any purpose only that for some reason it is
inexpedient to allow B to actuate it.
For example B may be a feeble rapidly varying telephonic current too feeble to
actuate a receiving telephone; in this case A is made to be a magnified image of B.
Again B may be a current in a straight wire b say an ordinary telegraph wire and a
the current obtained from coils made to rapidly rotate in the neighbourhood of the
wire. Again B may be the varying current in a coil & in circuit with a microphone,
this circuit being necessarily of small resistance and A the magnified or diminished
image of B may be produced in a circuit of any required resistance. Again B may
be a feeble telephone current & A may be a magnified image of B capable of working
a considerable number of telephones placed either in series or multiple are. Again B
may be a current sent along a telegraph line and A may be a greatly magnified
current working electric lamps the light from the lamps being automatically made to
vary greatly in strength for signalling or other purposes by variations made in the
weak current B sent along the telegraph line. In all these cases mechanical power
produced by hand or by a steam engine or an electromotor or any other motor is
converted into electrical power in the circuit a at a rate which is determined by the
electrical power which is being expended in the circuit b. The rate of revolution of
the coils a or their rate of motion of whatever kind it may be ought to be steady
but there are cases in which the image bought sometimes to more enlarged & some-
times less enlarged and in these cases the speed is increased and diminished periodically
or as demanded by circumstances.
In all these cases a may be regarded as the gramme or disc or drum armature of
a Dynamo-Machine, the current B being made to pass round the field magnet coils
and the image A obtained from brushes rubbing on the commutator.
Both a and b
may have iron parts like the iron of the armature & field magnet of a Dynamo-
Machine, but when A is to be an exact image of B it is desirable to dispense with
any iron in either a or b. The use of iron enables a great magnification of B to be

page_text: produced with even a small machine but in many cases the use of iron prevents A
being an exact image of B & hence the quantity of iron which we use is different in
machines designed for different purposes. In all cases when iron is used it must be in
such a divided state in both field magnet & armature as will cause the Foucault
currents to be as small as possible, otherwise the magnetic field in which the coils of
the armature rotate will not be in proportion to the current A flowing round the Field
Magnet Coils, or rather, changes in the Field will lag behind changes in the current
and the image produced will be a blurred image. In most of the cases to which our
invention is usefully applicable iron must be used in both a & b & the iron must be
in the shape of thin sheets or wires. We say, 'must be used,' having regard to the
necessity for smallness of size & cost.
In some cases, especially in Telephone work it is desirable that the current A
should be an exact image of the current B and in that case the armature a consists of
a simple disc of conducting material the current being obtained from a brush rubbing
its periphery and another its axle.
Again some parts of the system of coils called a¹ may be fixed relatively to 6 the
rest being moveable although the same current A passes through both fixed & move-
able parts. Any existing series dynamo whose external resistance is so great that the
machine cannot excite itself at the speed at which it is driven and which has in addition
an auxiliary coil b on the Field Magnet fed by an external current B is an illustration
of this form of our invention, a' being the series Field-Magnet coils through which
the current A passes and b the additional coil on the Field Magnet. Again some
parts of the system of coils called a¹¹ may be fixed relatively to b the rest being move-
able but the parts all are shunts to the other parts of a.. Any existing shunt Dynamo
which is not self exciting & which has in addition an auxiliary coil b on its Field
Magnet fed by an external current B is an illustration of this form of our invention.
Or again those parts of a which are fixed relatively to b may some of them be in series
with & some of them shunts to other parts of a. Any existing compound wound
dynamo or shunt dynamo or series dynamo which has an additional coil b fed by an
external current B is an illustration of our invention & as such would be readily
understood by any practical electrical engineer.
As our invention enables us to produce in a currents which represent to another or
the same scale currents in 6 however they may vary we adopt the following combination
when a sufficient scale of change of current is not produced in one operation:-The
original current B₁, is made in one or other of the ways already described to produce
the current A1, this current A₁ is used as the B, in a second machine to produce
current A, & so on; hence the final current A is the image of the original current B₁
but on a magnified or diminished scale.
a
Having now particularly described and ascertained the nature of our said Inven-
tion and in what manner the same is to be performed we declare that what
we claim is :-
1. The methods described for the employment of mechanical energy in producing
a more or less perfect image of an electrical current when any or all of the parts of a
and b have iron cores.
2. The methods described, when there are no iron cores to any of the parts.
E