Improvements in Electrical Transformers or Converters and in their Manufacture.
Year: 1891

page_text: Date of Application, 20th Jan., 1891
Complete Specification Left, 20th Nov., 1891-Accepted, 19th Jan., 1892
PROVISIONAL SPECIFICATION.
Improvements in Electrical Transformers or Converters and in their
Manufacture.
I, SEBASTIAN ZIANI DE FERRANTI, of 120 Fellows Road, Hampstead, in the
County of Middlesex, Electrician, do hereby declare the nature of this invention to
be as follows:-
In converters in which two sets of bars or strips are passed through the centre
of the primary and secondary coils and are doubled over outside these coils so that
each makes a complete ring as described in my former Patent No. 1514185 I use in
each set a number of such bars or strips set side by side at a distance apart so that
they form a series of iron rings with air spaces between them as described in that
Specification. I also separate the two sets of rings one from the other so that there
is an air space between them and I keep the two sets at the proper distance apart
and the rings in each set at the proper distance from one another by a division
plate which has projecting from each of its sides a series of clips or sockets into
which the sides of the rings are received. The series of clips or sockets on one
side of the plate being for holding the inner side of one series of rings and those on
the other for holding the inner side of the other series of rings. On the outer side
the rings are kept at the right distance apart by pins carried by the frame within-
which the converter is held.
Between the iron and the inner set of conductor coils of a converter I also
maintain an air space and also between this set of conductor coils and the next set
and if there are more sets an air space between each and also an air space between
the exterior of the outer coil and the portions of the iron rings which go outside
it-these air spaces not only serve to keep the coils cool but also to secure
improved insulation. For keeping the coils at the proper distance apart one from
the other and from the iron I employ distance pieces of insulating material placed
between them.
Each conductor coil is also subdivided into a number of parallel rings or
sections as described in the Specification above mentioned. In other forms of
converters the division of the coils and separation of the irons may similarly be
carried out.
In some cases the ventilation of the iron rings may be dispensed with and
provision even be made for hindering them from cooling so long as heat is
prevented from passing from them to the insulated conducting coils.
In addition to using distance pieces for separating the primary and secondary
coils from one another and from the iron and making air spaces between them I in
some cases use cylindrical divisions of cured ebonite or like insulating material
held midway between them in the centre of the air spaces.
Another method is to place the coils in concentric annular jars of insulating
material which are open at the top and then to seal over the top of the jars to
obstruct the leakage of current and prevent the entrance of moisture.
The annular concentric jars may all be formed together in one piece. When the
several coils have been enclosed within them the whole may be enclosed in an
annular metallic casing divided across to prevent the flow of induced currents
around it and the division packed to make a water tight joint.
In this way the
coils and their insulation are well protected whilst the iron is left exposed to the
air so that it may easily cool. The insulating divisions or shields may also be
made of a band of ebonite or like material wound around a mould of the desired
shape and then can be made with or without pressure externally to solidly divide
the mass.

page_text: The whole converter 1 embrace by a frame divided into four parts by vertical
and horizontal divisions and held one to the other by vertical and horizontal bolts
so that the frame can be contracted in either direction.
In a transformer or converter ventilated in either of the ways above mentioned
1 divide the primary or the secondary or both to prevent magnetic leakage.
Preferably I make the inner conductor coil a low tension coil and outside this a
high tension coil and again on the outside of this a low tension coil.
Each coil of a converter. I also make up of a series of spirals set side by side,
alternate coils being wound in opposite directions and the inner ends of every two
adjacent coils (one wound each way) coupled together so that they form a
continuous winding all in the same direction and when a number of such pairs of
coils are placed together side by side into the converter the outer ends only have to
be joined up to make one continuous coil.
Where two spiral coils are coupled together on the inside there will be but little
difference in potential in the current in the inner ends of these coils but at the
outside there will be considerable difference I therefore insert between them a disc
or ring of insulating material flanged sidewise on its outer edge outside the coils to
give a long space over which a spark if it passed at all would have to pass.
Similarly on the inside a flanged disc of insulation is inserted between such of the
outer coils as are coupled together on the outside.
The conductors I use are rectangular in cross section. The low tension
conductor in place of being a single rectangular bar I make up of a number of thin
strips placed one over the other and lightly insulated from one another preferably
by sulphurizing or fuming the several layers with sulphur fumes. The insulating
them in this way tends to prevent redistribution of current in the conductor,―that
is, to cause current to be carried by the central portions of the conductor as well
as by the outer portions.
Each spiral coil is wound separately some one way, some the other_with_the
Conductor and a strip of insulation wound in with it. The coils are then bound up
in or served with insulation and baked and pressed and moulded to form in a press
such as that presently described.
These are then connected up in pairs and a number of such tested pairs are put
one over the other and the necessary outside connections made between the pairs of
coils. This assemblage of tested pairs is next put on to an expansible mandril
whose four sides can be pressed apart from one another whilst plates are at the
same time forced against the four sides of the outer circumference of the ring and
other plates against the top and bottom so forming a complete mould within which
the pairs of coils can be pressed accurately into the shape required.
For pressing outwards the sides of the mandril I preferably use wedges passed
down through the top plate of the press. The plates which are pressed against the
exterior of opposite sides of the coils I preferably cause to be drawn together by
screw bolts.
Before or while pressing the rings the mould and rings held in it are slowly
heated until the shellac or insulating material between the several layers gets soft.
When heated the assemblage of coils is pressed between the plates and the surplus
shellac allowed to exude. In this way the coils are consolidated into one accurately
shaped block and occupy very much less space than they could otherwise be made
to occupy.
To prevent adhesion of the shellac to the plates of the press I interpose sheet
metal or other material between the coils and the press. When thin sheet metal
is used it can be readily stripped off from the shaped coil after it is removed from
the press.
When the block has been allowed to cool it is afterwards tested before being put
into the converter. A number of such blocks side by side are used in making up
each primary or secondary.
The thin iron strips of which each of the iron rings is made up may similarly be
stuck together by coating them with shellac or a mixture of paint and paste or

page_text: other gritty and adhesive materials and afterwards baking them into a firm solid
mass either before or after they have been bent to a U shape. The paint not only
holds the plates together but also prevents them from coming into actual contact
with one another, and made to form a solid bar except where the irons have
subsequently to be bent over the outside of the converter.
My invention also relates to transformers which are so designed as to give
constant currents through varying resistances which is generally effected by so
forming the iron magnetic circuit that a considerable number of the lines of force
produced in the primary coils do not pass through the secondary when a current
flows through the latter, that is, transformers in which the magnetic leakage is
purposely made considerable.
For the purpose of varying the amount of this leakage, I now propose to make
the primary and secondary coils moveable to or from each other along the iron
core which is made of sufficient length and suitable shape as to admit of this being
done, the coils may be made to slide one within the other to a greater or less
degree so as to be more or less under the influence of each other, the coils can also
be made so as to be subject to automatic alteration of position to effect any required
change or regulation in the current by suspending them by springs or some such
variable opposing force and relying on their mutual attraction or repulsion to alter
their relative positions. The above invention can also be applied to compound
wound transformers in which more than two circuits are employed and the relative
position of these several circuits and their mutual action and reaction can be varied
to any extent. These regulating transformers can be used either to maintain
constant current or for the regulation of meters, the regulation of "electro motive
force" and to be the equivalent of compound winding of dynamos when used in
connection with other transformers.
Dated this 20th day of January 1891
CARPMAEL & Co.,
Agents for the Applicant.
COMPLETE SPECIFICATION.
Improvements in Electrical Transformers or Converters and in their
Manufacture.
I, SEBASTIAN ZIANI DE FERRANTI, of 120 Fellows Road, Hampstead, in the
County of Middlesex, Electrician, 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 :-
In converters in which two sets of bars or strips are passed through the centre of
the primary and secondary coils and are doubled over outside these coils so that
each makes a complete ring as described in my former Patent No. 151418 I use in
each set a number of such bars or strips set side by side at a distance apart so that
they form a series of iron rings with air spaces between them as described in that
Specification. I also separate the two sets of rings one from the other so that there
is an air space between them and I keep the two sets at the proper distance apart
and the rings in each set at the proper distance from one another by a division plate
which has projecting from each of its sides a series of clips or sockets into which
the sides of the rings are received. The series of clips or sockets on one side of
the plate being for holding the inner side of one series of rings and those on the
other for holding the inner side of the other series of rings. On the outer side the
rings are kept at the right distance apart by pins carried by the frame within which
the converter is held.
Between the iron and the inner set of conductor coils of a converter I also
maintain an air space and also between this set of conductor coils and the next set
and if there are more sets an air space between each and also an air space between
the exterior of the outer coil and the portions of the iron rings which go outside

page_text: it these air spaces not only serve to keep the coils cool but also to secure
improved insulation. For keeping the coils at the proper distance apart one from
the other and from the iron I employ distance pieces of insulating material placed
between them.
Each conductor coil is also subdivided into a number of parallel rings or
sections as described in the Specification above mentioned. In other forms of
converters the division of the coils and separation of the irons may similarly be
carried out.
In addition to using distance pieces for separating the primary and secondary
coils from one another and from the iron and making air spaces between them I in
some cases use cylindrical divisions of cured ebonite or like insulating material
held midway between them in the centre of the air spaces.
The whole converter I embrace by a frame divided into four parts by vertical
and horizontal divisions and held one to the other by vertical and horizontal bolts so
that the frame can be contracted in either direction.
In the annexed drawings a transformer or converter is represented in which the
above mentioned parts of my invention are applied.
a a are the
Figure 1 is a side elevation. Figure 2 is a section on the line A B in Figure 1
and Figure 3 is a horizontal section on the line C D in Figure 2.
primary coils; they are as previously stated subdivided into a number of parallel
rings one over the other, but this the drawing does not show, and 666 are the
secondary coils which in this case are arranged in two sets, one within and the
other without the primary coils. c¹ c¹ c² care iron core bars or rather bundles of
iron bands which are passed through the coils and then folded on themselves to
form rings as is described in the Specification of my former Patent. On either
side of the converter a series of separate core rings are provided with air spaces
between them to admit of any heat which may be generated being readily
dissipated. d is a division plate between the two sets of core rings, it has clips or
sockets dd upon it to keep the core rings in place. ee are pins on the external
frame which enter between the core rings and aid in retaining them in their proper
positions. is a cylinder or rather a tube nearly rectangular in transverse section,
through which the core rings and the division plate pass and which separates the
core rings from the secondary coils. The cylinder is preferably of cured
vulcanite. is another similar cylinder but of larger size so that it may surround
and contain within it the coils . gg are strips of vulcanite on either side of the
coils keeping them in place between the cylinders ff' and preserving air spaces.
2 is another vulcanite cylinder coutaining the primary coils a a and g¹ g₁ are
vulcanite strips preserving air spaces on either side of the primary coils and
between them and the cylinders f¹². Similarly f is an outer cylinder containing
the set of secondary coils and g g are strips preserving air spaces around
them and retaining them in place. hare vulcanite strips, shewn also in Figure 4,
inserted beneath the coils and between them and the core rings. i is a base on
which the converter stands and k k are two side bars forming part of the frame or
case in which the converter is contained. are horizontal bolts connecting the
bars kk and serving to draw them together to embrace the core rings tightly; they
also connect the side strips to the bars k. k* * * are other similar
parts at the upper part of the case or frame. The bolts k¹¹x pass through the
division plate d and hold it in place. are loops by which the converter may
be lifted. The side strips ³ ³ come together half way up the converter, here
they are rivetted to angle irons k* and these are drawn together by bolts to tighten
the frame or case upon the core rings in a vertical direction.
In place of employing separate ebonite cylinders ƒ ƒ &c. another method
illustrated by Figure 5 is to place the coils in concentric annular jars of insulating
material which are open at the top and then to seal over the top of the jars to
obstruct the leakage of current and prevent the entrance, of moisture.
In this figure a a are the primary coils, bare the secondary coils and c c are
the iron core rings.

page_text: The annular concentric jars may all be formed together in one piece. When the
several coils have been enclosed within them the whole may be enclosed in an
annular metallic casing which is not shewn in the figure but which fits the jars
closely. This casing is divided across to prevent the flow of induced currents
around it and the division packed to make a water tight joint. In this way the
coils and their insulation are well protected whilst the iron is left exposed to the
air so that it may easily cool.
The insulating divisions or shields may also be made of a band of ebonite or like
material wound around a mould of the desired shape and then can be made with or
without pressure externally to solidly divide the mass.
I build up the converter coils in the following manner; Each coil of a converter
I make up of a series of spirals or volutes set side by side, alternate coils being
wound in opposite directions and the inner ends of every two adjacent coils (one
wound each way) coupled together so that they form a continuous winding all in
the same direction and when a number of such pairs of spirals are placed together
side by side into the converter the outer ends only have to be joined up to make
one continuous coil.
The conductors which I employ are rectangular in section. I first wind the
conductor upon itself into a spiral or volute corresponding in dimensions to the coil
required and with a ribbon of insulating material such as cotton fabric saturated
with shellac between the convolutions.
Each spiral is wound separately some one way, some the other with the con-
ductor and a strip of insulation wound in with it. The spirals are then bound-up
in or served with insulation and baked and pressed and moulded to form in a press
such as that presently described.
These are then tested and connected up in pairs each consisting of a right and a
left spiral and a number of such tested pairs are put one over the other and the
necessary outside connections made between the pairs of spirals.
Where two spiral coils are coupled together on the inside there will be but little
difference in potential in the current in the inner ends of these coils but at the
outside there will be considerable difference I therefore insert between them a disc
or ring of insulating material flanged sidewise on its outer edge outside the coils to
give a long space over which a spark if it passed at all would have to pass.
Similarly on the inside a flanged disc of insulation is inserted between such of the
outer coils as are coupled together on the outside.
This assemblage of tested pairs is next put on to an expansible mandril whose
four sides can be pressed apart from one another whilst plates are at the same time
forced against the sides of the outer circumference of the ring and other plates
against the top and bottom so forming a complete mould within which the pairs of
coils can be pressed accurately into the shape required.
For pressing outwards the sides of the mandril I preferably use wedges passed
down through the top plate of the press. The plates which are pressed against the
exterior of opposite sides of the coils I preferably cause to be drawn together by
screw bolts.
Before or while pressing the rings the mould and rings held in it are slowly
heated until the shellac or insulating material between the several layers gets soft.
When beated the assemblage of coils is pressed between the plates and the surplus
shellac allowed to exude. In this way the coils are consolidated into one accurately
shaped block and occupy very much less space than they could otherwise be made
to occupy.
To prevent adhesion of the shellac to the plates of the press 1 interpose sheet
metal or other material between the coils and the press. When thin sheet metal is
used it can be readily stripped off from the shaped coil after it is removed from the
press.
When the block has been allowed to cool it is afterwards tested before being put
into the converter. A number of such blocks side by side are used in making up
each primary or secondary.

page_text: Figure 6 is a horizontal section and Figure 7 is a transverse vertical section of
the press and Figure 8 is a longitudinal section of the head or upper part.
m is the base of the press, n is the head, oo are screw bolts by which the head
can be drawn down towards the base, ppare four plates forming the expanding
mandril upon which the coils to be compressed and moulded are placed. 99 are
wedges which when driven down force the plates pp outwards, r is a coil or pile of
spirals or volutes in place in the press. In addition a clamp not shewn in the
drawing is employed; it consists of two bars or plates which are drawn together by
bolts at their ends and are so made to compress the exterior of the coil along its
two outer sides. At the ends the coils may be left free on the exterior but every-
where else they are accurately moulded to shape.
The thin iron strips of which each of the iron rings is made up may similarly be
stuck together by coating them with shellac or a mixture of paint and paste or
other gritty and adhesive materials and afterwards baking them into a firm solid
mass either before or after they have been bent to a U shape. The paint not only
holds the plates together but also prevents them from coming into actual contact
with one another, and made to form a solid bar except where the irons have
subsequently to be bent over the outside of the converter."
The low tension conductor in place of being a single rectangular bar I make up
of a number of thin strips placed one over the other connected in parallel and
lightly insulated from one another preferably by sulphurizing or fuming the several
layers with sulphur fumes. The insulating them in this way tends to prevent
redistribution of current in the conductor, that is, to cause current to be carried by
the central portions of the conductor as well as by the outer portions.
My invention also relates to transformers which are so designed as to give
constant currents through varying resistances which is generally effected by so
forming the iron magnetic circuit that a considerable number of the lines of force
produced in the primary coils do not pass through the secondary when a current
Hows through the latter, that is, transformers in which the magnetic leakage is
purposely made considerable.
For the purpose of varying the amount of this leakage, I now propose to make
the primary and secondary coils moveable to or from each other along the iron
core which is made of sufficient length and suitable shape as to admit of this.
Figure 9 shews such a converter, a is the primary coil, 6 is the secondary coil
which is moveable to and from the primary coil and c c are the iron core rings
passing through the two coils. Or the coils may be made to slide one within the
other to a greater or less degree so as to be more or less under the influence of
each other, the coils can also be made so as to be subject to automatic alteration of
position to effect any required change or regulation in the current by suspending
them by springs or some such variable opposing force and relying on their mutual
attraction or repulsion to alter their relative positions. The above invention can
also be applied to compound wound transformers in which more than two circuits
are employed and the relative position of these several circuits and their mutual
action and reaction can be varied to any extent. These regulating transformers
can be used either to maintain constant current or for the regulation of meters, the
regulation of "electro motive force" and to be the equivalent of compound winding
of dynamos when used in connection with other transformers.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is:
-
1. In an electrical transformer or converter in which two sets of bars or strips
are passed through the primary and secondary coils and are doubled over outside
these coils so that they make complete rings; maintaining air spaces between the
rings of the two sets of core rings substantially as described.
2. Providing a division plate between the core rings with clips or sockets 'to
receive the rings and keep them in place substantially as described,

page_text: 3. Providing pins on the exterior frame projecting between the core rings to aid
in keeping them in place substantially as described.
4. Maintaining air spaces separating the core rings from the coils substantially
as described.
5. Maintaining air spaces everywhere between primary and secondary coils sub-
stantially as described.
6. Separating the primary and secondary coils and the core rings by cylindrical
divisions of cured vulcanite or like insulating material located in the air spaces
between them substantially as described.
7. Separating the primary and secondary coils and the core rings by placing the
coils in concentric annular jars of insulating material substantially as described.
8. Enclosing the primary and secondary coils within an air tight annular metal
case and applying the iron core rings through and around this case substantially as
described.
9. Enclosing the whole converter in a frame divided horizontally and vertically
into four parts so held together that the frame can be contracted in either direction
substantially as described.
10. Dividing one or both of the coils into sets so that the primary is between
two secondary coils or vice versa to prevent magnetic leakage substantially as
described.
11. The low tension conductor made up of thin strips connected in parallel
lightly insulated from one another by sulphur fuming or otherwise substantially as
described.
12. An electrical converter or transformer with coils formed of conductors of
rectangular section wound in spirals or volutes together with bands of insulating
material and enveloped in insulating material substantially as described.
13. An electrical transformer or converter with coils built up in alternate right
and left hand spirals or volutes laid one against the other with ends connected
to make complete coils continuous in and out from the centre substantially as
described.
14. An electrical transformer or converter with coils moulded to form by the aid
of heat aud pressure substantially as described.
15. An electrical transformer or converter with coils containing conductors of
rectangular section wound with insulating material into spirals or volutes laid one
against the other and moulded and pressed to form substantially as described.
16. Apparatus substantially as described for moulding the coils of transformers
or converters.
17. An electrical transformer or converter with moveable coils arranged in such
manner as to admit of adjustment or regulation of the magnetic leakage sub-
stantially as described.
Dated this 20th day of November 1891.
CARPMAEL & Co.,
Agents for the Applicant.