An Improved Electrical Transformer for Currents of High Potential and Variable Frequency.
Year: 1898

page_text: PROVISIONAL SPECIFICATION.
An Improved Electrical Transformer for Currents of High Potential
and Variable Frequency.
We, ALFRED WYDTS and OCTAVE MAXIMILIEN ROCHEFORT, both of 46, Boulevard
Haussmann, Paris, in the Republic of France, Engineers, do hereby declare the
nature of this invention to be as follows:-
:-
This invention relates to a novel electrical induction transformer of the
Ruhmkorff type, especially applicable to the production of Crookes's radiations, to
obtaining currents of high frequency, to ignition by the induction spark, to the
operation of commercial and medical ozonaters and so forth.
The primary circuit is formed by a relatively large and short wire making a small
number of turns around a central core of annealed iron wires which are insulated
one from the other, in order to obviate, to a certain extent, the production of
Foucault's currents and at the same time diminish "hystérésis."
This primary coil is enclosed in a tube of glass, crystal or any other suitable
insulating substance and held in a central position by means of two washers of
fibre or other insulating material, in such a manner that between the wires and the
internal wall of the tube a free space is left into which is run an insulating
substance.
The glass tube is itself supported by brackets suitably shaped for its reception,
or in any other appropriate manner, at the centre of a vessel composed of an insu-
lating substance such as glass, celluloid, porcelain or the like, which is subse-
quently filled with the insulating substance.
Upon the tube is arranged the secondary circuit composed in the following
manner:
A certain number (according to the power of the apparatus) of elementary coils,
constructed in the manner which is hereinafter explained, is arranged upon the
glass tube; the coils are all connected in series and the two free end wires are con-
nected to the secondary terminals of the apparatus, of which they constitute the
two poles.
The secondary coils are formed in the following manner:
or 6
Upon a wooden mandrel, which is slightly conical in form so as to facilitate the
dismounting of the coils, and which is mounted upon a disc or wheel which, in
turning travels at the same time in the direction of its length, are stuck
sheets of paper which have been carefully paraffined and cut into strips of the
same width as the elementary coils. These sheets of paper are superposed so as to
form a paper tube of considerable strength, it will however be understood that this
core may also be formed of card board, wood or the like without affecting the result
obtained.
When this core has been formed, the coiling of the secondary wire may be
commenced, care being taken to leave between each turn a slight interval which
is afterwards filled up by the insulating substance. This first layer is then covered

page_text: by two sheets of paraffined paper between which the insulating substance is also
interposed and a second layer is then formed, and so on; the coil being completed
by the application of 4 or 5 sheets of paraffined paper.
These coils are then submitted to an immersion of twenty four hours in a hot
solution of paraffin in petroleum in variable proportions.
They are then cooled in this bath from which they are withdrawn for fixing
upon the tube. They are then suitably connected so as to form the secondary
circuit.
When the whole of the primary and secondary systems has been mounted and
fixed in the receptacle this latter is filled with a solution of paraffin in petroleum,
in such a manner as to completely immerse the primary and secondary coils, and
this solution is maintained in a heated condition for several hours.
The secondary wires issue through tubes from this bath of paraffined petroleum
which sets into a jelly upon cooling. These tubes may be of thick crystal or of any
other suitable insulating substance. Terminals which serve to collect the secon-
dary current are mounted at the ends of these tubes; they may be of any suitable
kind.
In powerful annaratus, these tubes are made up of two concentric tubes closed
one upon the other at each extremity. The space between is filled with insulating
medium in a liquid or pasty condition, whilst through the central portion which
is left free passes the secondary wire.
When the apparatus is less powerful, and the ordinary Ruhmkorff winding can
be readily employed, that is to say with the secondary circuit merely insulated with
gum lac the interposition of a tube similar to that above described, but of larger
dimensions, between the primary and secondary circuits, permits, whilst avoiding
the secondary derivations which are produced in the forms of emanations into the
metallic mass of the primary circuit, of increasing in considerable proportions the
output of the secondary coils.
After a great number of experiments we have found that it is essentially a com-
pact insulation which it is necessary to effect in order to avoid the secondary
derivation which have hitherto been inevitable with currents of very high pres-
sure. In fact, crystal which has about 1500 times the resistance of our insulating
medium, may be traversed with extreme facility in thicknesses which are from
four to five times those at which our insulating medium possesses absolute resis-
tance.
The mixture which we employ is however specifically of smaller resistance than
crystal after a certain duration of electrisation, but it is in a semiliquid gelatinous
state which, unlike even the densest crystal, does not present numerous pores
through which sparks so readily force a passage.
The liquid insulation which is readily obtained by immersing the apparatus
which it is desired to insulate in a bath of oil of any kind, whether mineral or
not, ceases to give good results with very high pressures and even with quite
ordinary pressures. It does not, it is true, possess the disadvantage of porosity,
but it has another which is equally prejudicial: the molecules which constitute
the liquid become positively and negatively electrised in the vicinity of the ex-
treme secondary poles, and owing to the extreme mobility of the insulating medium
these molecules violently attract each other and re-constitute, in the form of a
rapid quivering of the liquid, the two electricities. If the frequency of the in-
ducing current increases, the shock of the molecules becomes sufficiently consider-
able to produce projections of the liquid, if the frequency still increases the
quivering becomes more confined, more rapid, but less visible, becoming quite
invisible with extremely high frequencies, but being always injurious.
The trembler or interruptor which alternately establishes and interrupts the
current in the primary circuit is composed of a copper or aluminium balance
inserted in a small mass of copper in which it is able to slide and fixed in the
desired position by a set screw, a plunging contact of iron or platinum is provided
which establishes contact with the mercury contained in a vessel. At the other

page_text: extremity of the balance is the iron armature which is intended to be alternately
attracted by the electro-magnet.
The point successively enters and leaves the mercury bath as a consequence of
the successive oscillatory movements of the beam which is supported by the
straight spring, one end of which is inserted in the mass and the other in the
supporting foot.
We provide a spring fixed upon the bean and furnished with a small plate of
platinum upon its upper portion. A screw having a platinum point serves to con-
duct the current to the point of contact with the platinum spring.
This screw may, at the same time as it is raised or lowered by un-screwing or
screwing it in its support, be laterally displaced and make contact wth the platinised
spring at any point upon this latter, thus either approaching or receding from the
centre of the beam.
The electro-magnet may be either raised or lowered by means of a milled knob
actuating a pinion gearing with the rack.
The mercury cup may also be raised or lowered by means of a similar arrange-
ment.
The oscillation of the beam takes place in the following manner:
The current
of a battery cell, for example enters through the screw of the trembler which
conducts the current to the platinised spring; the current passing through the
beam, the mass and the spring passes out from the foot to the electro-magnet
which it leaves and proceeds to the second pole of the battery cell in question.
Under the conditions just described, the current circulates and the electro-magnet
attracts its armature the beam having been depressed towards the right hand by
this movement breaks the contact which existed between the screw and the spring,
the current no longer enters the electro-magnet which ceases to attract its armature
so that the original conduction of things exists, thereupon the screw again makes
contact with the spring, and so on in succession.
Where radiography is concerned it is of the highest importance that the
frequency of the currents should be variable; the radiography tubes only give their
maximum of X rays with a predetermined frequency, which explains the very
poor results given by first class tubes and coils having a fixed frequency, because
the current interruptions of these latter are not suitably proportioned to the tubes
experimented with.
It is thus of the greatest importance to be able to cause this frequency to vary
whilst operations are in progress, and this is obtained with the greatest ease by
lateral displacement of the screw. The more this screw is pushed in the proper
direction, the greater becomes the rapidity of the trembler. The spring becoming
less flexible in proportion as its foot is approached, no longer permits the screw
to remain long in contact and this latter always rests slightly upon it, from which
results an acceleration of the movements of the beam.
The intensity of the attraction of the armature also exerts considerable influence
upon the rapidity of the interruptions; it should neither be too abrupt nor too
weak in order that the rupture of the primary current may take place normally at
the contact. In order to readily obtain the necessary magnetic adjustment, the
electro-magnet is raised and lowered as above indicated.
The principal current which serves to excite the primary circuit of the coil enters
through the foot, passes through the spring, the beam and the plunging contact
then enters the mercury bath, whence it passes into the primary coil through
the supporting foot of the mercury cup.
The mercury is covered by a stratum of ethylic alcohol whilst the apparatus
is in action.
As in Ruhmkorff's coil, a condenser is employed, the armatures of which are
respectively in communication with the two electrodes between which passes the
spark on the rupture of the primary circuit, in order to absorb a portion of the
extra current, and to render shorter the cessation of the current in the inducing
circuit.

page_text: It has been observed that the period of rupture should be shorter than the period
during which the current is closed in the primary circuit, and this in a manner
which is variable with the intensity of the current employed, the self induction of
the primary circuit and so forth.
The best conditions of duration and rupture of contact may be obtained by
adjusting the height of the mercury cup by means of the knob actuating the rack
which supports the cup.
1000
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C.,
Agents for the Applicants.
An Improved Electrical Transformer for Currents of High Potential
and Variable Frequency.
We, ALFRED WYDTS and OCTAVE MAXIMILIEN ROCHEFORT, both of 46, Boulevard
Haussmann, Paris, in the Republic of France, Engineers, 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 to a novel electrical induction transformer of the
Ruhmkorf type, especially applicable to the production of Crookes's radiations, to
obtaining currents of high frequency, to ignition by the induction spark, to the
operation of commercial medical ozonaters and so forth.
In order that our invention may be readily and clearly understood we have
represented the same in the accompanying drawing.
The primary circuit is formed by a relatively large and short wire A, making a
small number of turns around a central core B of annealed iron wires which are
insulated one from the other, in order to obviate, to a certain extent, the produc-
tion of Foucault's currents and at the same time diminish "hysteresis."
This primary coil is enclosed in a tube C of glass, crystal or any other suitable
insulating substance and held in a central position by means of two washers D D
of fibre or other insulating material, in such a manner that between the wires and
"the internal wall of the tube a free space E is left into which is run an insulating
substance.
The glass tube C is itself supported by brackets F suitably shaped for its recep-
tion, or in any other appropriate manner, at the centre of a vessel L composed of
an insulating substance such as glass, celluloid, porcelain or the like, which is
subsequently filled with the insulating substance.
Upon the tube C is arranged the secondary circuit composed in the following
manner:
A certain number (according to the power of the apparatus) of elementary
coils G G... constructed in the manner which is hereinafter explained, is
arranged upon the glass tube C; the coils are all connected in series and the two
free end wires H, H are connected to the secondary terminals of the apparatus, of
which they constitute the two poles.
The secondary coils G are formed in the following manner;
Upon a wooden mandrel, which is slightly conical in form so as to facilitate the
dismounting of the coils, and which is mounted upon a disc or wheel which, in
turning. travels at the same time in the direction of its length, are stuck 5 or 6
sheets of paper which have been carefully paraffined and cut into strips of the
same width as the elementary coils. These sheets of paper are superposed so as to

page_text: form a paper tube of considerable strength; it will however be understood that this
core may also be formed of cardboard, wood or the like without affecting the result
obtained.
When this core has been formed, the coiling of the second wire may be com-
menced, care being taken to leave between each turn a slight interval which is after-
wards filled up by the insulating substance. This first layer I is then covered
by two sheets of paraffined paper between which the insulating substance is also
interposed, and a second layer K is then formed, and so on; the coil being com-
pleted by the application of 4 or 5 sheets of paraffined paper.
These coils are then submitted to an immersion for twenty four hours in a hot
solution of paraffine in petroleum in variable proportions.
They are then cooled in this bath from which they are withdrawn for fixing
upon the tube. They are then suitably connected so as to form the secondary
circuit.
When the whole of the primary and secondary systems has been mounted and
fixed in the receptacle L, this latter is filled with a solution of paraffine in petroleum,
in such a manner as to completely immerse the primary and secondary coils, and
this solution is maintained in a heated condition for several hours.
The secondary wires issue through tubes M M from this bath of paraffined
petroleum which sets into a jelly upon cooling. These tubes may be of thick
crystal or of any other suitable insulating substance. Terminals which serve to
collect the secondary current are mounted at the ends of these tubes; they may
be of any suitable kind.
In powerful apparatus, these tubes are made up of two concentric tubes P
(Figure 2) closed one upon the other at each extremity. The space O between is
filled with insulating medium in a liquid or pasty condition, whilst through the
central portion which is left free passes the secondary wire Q R.
When the apparatus is less powerful, and the ordinary Rulmkorff winding can
be readily employed, that is to say with the secondary circuit merely insulated
with gum lac the interposition of a tube similar to that shewn in Figure 2, but
of larger dimensions, between the primary and secondary circuits permits, whilst
avoiding the secondary derivations which are produced in the forms of emanations
into the metallic mass of the primary circuit, of increasing in considerable
proportions the output of the secondary coils.
After a great number of experiments we have found that it is essentially a
compact insulation which it is necessary to effect in order to avoid the secondary
derivation which have hitherto been inevitable with currents of very high pressure
in fact, crystal which has about 1500 times the resistance of our insulating medium,
may be traversed with extreme facility in thicknesses which are from four to five
times those at which our insulating medium possesses absolute resistance.
The mixture which we employ is however specifically of smaller resistance than
crystal after a certain duration of electrisation, but it is in a semiliquid gelatinous
state which, unlike even the densest crystal, does not present numerous pores
through which sparks so readily force a passage.
The proportions that we employ in order to obtain a good insulating mixture
consists in utilising three parts of paraffine to one of petroleum.
The liquid insulation which is readily obtained by immersing the apparatus
which it is desired to insulate in a bath of oil of any kind, whether mineral or
not, ceases to give good results with very high pressures and even with quite
ordinary pressures. It does not, it is true, possess the disadvantage of porosity,
but it has another which is equally prejudicial; the molecules which constitute
the liquid become positively and negatively electrised in the vicinity of the ex-
treme secondary poles, and owing to the extreme mobility of the insulating medium,
these molecules violently attract each other and re-constitute, in the form of a
rapid quivering of the liquid, the two electricities. If the frequency of the in-
ducing current increases, the shock of the molecules becomes sufficiently consider-
able to produce projections of the liquid, if the frequency still increases the

page_text: quivering becomes more confined more rapid, but less visible, becoming quite
invisible with extremely high frequencies, but being always injurious.
The trembler or interruptor which alternately establishes and interrupts the
current in the primary circuit is composed of a copper or aluminium balance A
(Figure 3) inserted in a small mass of copper 13 in which it is able to slide and
be fixed in the desired position by a set screw C¹; and D' is the plunging contact
of iron or platinum which established contact at E with the mercury F¹ contained
in the vessel G¹. At the other extremity of the balance is the iron armature H
which is intended to be alternately attracted by the electromagnet I¹.
The point E successively enters and leaves the mercury bath F" as a consequence
of the successive oscillatory movements of the beam A which is supported by the
straight spring O¹, one end of which is inserted in the mass B and the other in
the supporting foot J¹.
K is a spring fixed upon the beam and furnished with a small plate of
platinum L upon its upper portion. A screw M¹ having a platinum point serves
to conduct the current to the point of contact with the platinised spring. This
screw may, at the same time as it is raised or lowered by unscrewing or screwing
it in its support, be laterally displaced along the line a¹¹ and make contact with
the platinised spring at any point upon this latter, thus either approaching or
receding from the centre of the beam.
The electro magnet I may be either raised or lowered by means of a milled knob
actuating a pinion gearing with the rack N¹.
The mercury cup G¹ may also be raised or lowered by means of a similar arrange-
ment shewn in Figure 3.
Where radiography is concerned it is of the highest importance that the frequency
of the currents should be variable; the radiographic tubes only give their maximum
of X rays with a pre-determined frequency which explains the very poor results
given by first class tubes and coils having a fixed frequency, because the current
interruptions of these latter are not suitably proportioned to the tubes experimented
with.
It is thus of the greatest importance to be able to cause this frequency to vary
whilst operations are in progress, and this is obtained with the greatest ease by
lateral displacement of the screw M¹ along the line a¹ b¹. The more this screw
is pushed towards a, the greater becomes the rapidity of the trembler. The
spring K L becoming less flexible in proportion as its foot is approached, no
longer permits the screw M¹ to remain long in contact and this latter always rests
slightly upon it, from which results an acceleration of the movement of the beam.
The intensity of the attraction of the armature also exerts considerable influence
upon the rapidity of the interruptions; it should neither be too abrupt nor too
weak in order that the rupture of the primary current may take place normally
at E. In order to readily obtain the necessary magnetic adjustment, the electro
magnet is raised and lowered as above indicated.
The primary current leaves the positive pole of the battery, reaches the vertical
upright through the wire 5, then passes along the branch A¹ to the rod D im-
mersed in the mercury. Thence it passes along the wire 6 to the primary wind-
ing E, which it leaves by the left hand terminal A and returns to the negative
pole of the battery.
The circuit of the magnet I' is as follows:-the positive pole of the battery,
upright J, lever arm A, spring L₁ screw M', wire 1, then the wire 4, electro
magnet 1, wire 3 and finally the wire 2.
As soon as the current traverses the electro magnet this latter contracts its arma-
ture. The shunt circuit is then opened by the spring L and immediately the
lever A returns to its original position, thus causing a series of interruptions
which produce the opening of the primary circuit by the rod D and the mercury.
These sudden ruptures in the primary circuit give in the secondary circuit H H
a current which is hereafter utilised.

page_text: The mercury is covered by a stratum of ethylic alcohol whilst the apparatus
is in action.
As in Ruhmkorff's coil, a condenser is employed, the armatures of which are
respectively in communication with the two electrodes between which passes the
spark on the rupture of the primary circuit, in order to absorb a portion of the
extra current, and to render shorter the cessation of the current in the inducing
circuit.
It has been observed that the period of rupture should be shorter than the period
during which the current is closed in the primary circuit, and this in a manner
which is variable with the intensity of the current employed, the self induction
of the primary circuit and so forth.
The best conditions of duration and rupture of contact may be obtained by ad-
justing the height of the mercury cup by means of the knob actuating the rack
which supports the cup.
Having now particularly described and ascertained the nature of our said in-
vention and in what manner the same is to be performed, we declare that what we
claim is:-
:-
1. With the object of obtaining an electric transformer for currents at a high
potential and having a variable frequency; (a) A primary circuit formed by a
series of turns around an iron wire core lodged within a tube of insulating material,
with interposition of insulating material between the walls of the tube
and the winding. (b) A secondary circuit, the coils of which are
formed by windings of wire with the interposition, between each
winding, of sheets of paraffined paper, the said coils after having undergone an
immersion of about 24 hours in a hot solution of paraffine in petroleum being con-
nected in series, the two free wires passing to the interior of a tube of some insu-
lating substance which, for powerful apparatus, may be formed by two concentric
tubes with interposition of an insulating substance.
2. In the high pressure and variable frequency electrical transformer described
in Claim 1. the immersion of a primary and a secondary circuit, arranged as above
described, in a jelly formed by the cooling of a hot solution of paraffine in
petroleum, of any other substance which is capable of forming a jelly on cooling,
as above specified.
3. The combination with the high pressure, variable frequency electrical trans-
former described in the preceding claims, of an interruptor formed by a metal
beam provided at one of its extremities with an iron armature intended to be
attracted by the electro magnet when traversed by the current, and at its other
extremity with a metal point entering a cup of mercury, the beam or balance thus
constituted being supported by a vertical spring, the positions of the electro-
magnet and mercury cup being capable of adjustment by means of racks provided
for that purpose as above specified.
4. In the current interruptor described in Claim 3, a screw capable of vertical
and lateral displacement above a flat spring fixed upon the heam and enabling the
speed to be regulated whilst the apparatus is in operation, as above specified.
Dated this 12th day of October 1898.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C.,
Agents for the Applicants.