Improvements in Electrical Transformers, and Apparatus connected therewith.
Year: 1894

page_text: Date of Application, 4th Jan., 1894
Complete Specification Left, 4th Oct., 1894-Accepted, 4th Feb., 1895
PROVISIONAL SPECIFICATION.
Improvements in Electrical Transformers, and Apparatus connected
therewith.
SEBASTIAN ZIANI DE FERRANTI, of 27, Charterhouse Square in the County
of London, Electrical Engineer do hereby declare the nature of this invention to
be as follows:-
This invention has for its object improvements in electrical converters which are
designed to take a constant electromotive force and varying quantity of current
and to give out a constant quantity of current or approximately so, with a varying
electromotive force according to the resistance of the work put upon their circuits
or the resistance of the work to be done.
It also relates to converters which cannot under any circumstances give more
than a certain quantity of current, the said converters being specially applicable
for transforming currents for use with rectifiers.
According to this invention I form a magnetic circuit of the converter of a
central core, ends and connecting bars. The central core is preferably circular and
the coils are of large diameter and of flat section.
the core.
I fix either the primary or the secondary windings in one block on the centre of
The other coils either primary or secondary are suspended by vertical
rods above and below the fixed coils and there is sufficient space left upon the core
for these to be moved several inches up and down.
The movable coils hang clear of the core and connecting bars. The vertical
rods which carry the coils work in guides but are not rigidly connected to the coils.
The movable coils are held by means of split bands strapped round about the
coils, the coils being made on their outer edge of a conical shape so that they may
be gripped and securely held by the bands drawn tightly round them.
In order to connect the bands supporting the coils with the vertical rods I make
a flexible coupling in 3 places. This coupling enables the coils to be supported at
3 points giving them a slight lateral play so that nothing may bind in the working.
The movable coils above and below the fixed coils consist of about an equal
weight of copper winding and the mechanism is so arranged that the one set of
coils balances the other, and also so that when the upper coils move away from the
fixed ones upwards the lower coils move away from the fixed coils downwards.
The 3 rods above mentioned which support the upper coils are connected to a
metal star. The 3 rods which support the lower coils are hung upon knife edges
and beams whose other ends are connected to the star supporting the upper coils.
The converter is so arranged that the tendency is for the coils to fall together by
the preponderance of the weight placed upon the star and this tendency is counter-
balanced by the repulsion of the movable coils from the centre coil when the
current flows.
The star is guided and is formed with a cylinder which fits on to a vertical piston
upon which it moves. This piston and cylinder act as a dash pot to prevent any
violent motion of the coils and so make the apparatus workable.
When the current flows in the coils a certain repulsion takes place. So long as
the current is normal the coils remain close together, if the current becomes too
strong the coils separate and the electro-motive force is reduced and consequently
the current is diminished.
The converter is practically self-regulating, any additional regulation which
is required is done by means of adding or diminishing the weight on the star. This

page_text: can conveniently be done by hand but it may also be done by any well-known
mechanism worked by a relay where great automatic accuracy is required.
The irons of the end and connecting side bars I form of laminated sheet iron
pressed into heavy metal cheeks which keep the laminated iron in shape and enable
the machine to be mechanically fitted together.
The upper and lower castings also carry the supports for the knife edges of the
swing beams and guides for the vertical rods which support the coils.
Under certain circumstances I may modify the above arrangement by using two
circular or as nearly circular as possible vertical cores and connecting them at the
top and bottom with single blocks of soft iron sheets. The magnetic circuit is then
exactly like that of a Gramme ring without poles but is rectangular in form. By
this means I can wind coils of half the external diameter which it is otherwise
necessary to use and use two for every one which would be used on the before
described plan.
There are fixed coils on each vertical core and also movable coils on each
vertical core.
This arrangement is a more economical one in the way of magnetic
circuit and of copper required, the coils under these circumstances being held
rather differently in the arrangement of bands and supporting rods but the principle
is in both cases the same.
I use converters made in this way in connection with apparatus for rectifying the
direction of the current, namely for making alternating current into direct current.
Such apparatus I have described in my Patent No. 17,220 1891.
In certain cases I may place a condenser in series with the converter above
described so as to counter-balance the self-induction of the apparatus and reduce
the apparent loss. The condenser also has the capacity of helping to regulate the
quantity of current which can flow.
The great object of this invention is to so build the converter and so shape the
coils that when working on full load the primary and secondary coils may be as
nearly co-incident i.e., that they may be brought as close together to form a solid
mass as is mechanically possible so as to avoid a too great leakage of the magnetic
field when the converter is desired to give a large output. On the other hand when
it is desired to get a small output from the converter the coils must so separate
from each other that a complete leakage of the magnetic field takes place. In
order to accomplish this as above explained I prefer to make the coils of as flat a
section as possible so that when the primary and secondary coils are all bunched
together they approximate to a square section.
Another method of accomplishing the same result is to wind say the primary coil
next to the central core and occupying a space equal to half the length of the core
and then wind the secondary coil outside this, both coils being clear of each other
and of the central core, so that when the primary moves up and the secondary
moves down the two are end to end upon the core.
Another modification of this is to wind the primary coil close to the core and fix
it in the centre and to make the secondary coils in two halves of a larger diameter
so that when they are close together they envelop the primary coil, when they move
apart they will occupy a place on the core clear of the primary coil and considerable
leakage will take place.
Again I may modify this arrangement by winding the primary coil on the core
and of the section of a right angle triangle with its longest side to the core the
secondaries are then wound in two separate coils which are of a right angle triangle
section with their longest side next to the side of the primary coil. These coils
are balanced and move up and down as above explained.
There are many obvious methods of carrying out the invention herein stated but
I have confined myself to describing those of greatest practical value.
In most cases it is immaterial whether the primary or secondary coils occupy the
position nearest to the centre core.
Dated this Third day of January 1894.

page_text: Improvements in Electrical Transformers, and Apparatus connected
therewith.
SEBASTIAN ZIANI DE FERRANTI, of 27, Charterhouse Square, in the County
of London, Electrical Engineer 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 has for its object improvements in electrical converters which are
designed to take a constant electromotive force and varying quantity of current
and to give out a constant quantity of current or approximately so, with a varying
electromotive force according to the resistance of the work put upon their circuits
or the resistance of the work to be done.
It also relates to converters which cannot under any circumstances give more
than a certain quantity of current, the said converters being specially applicable
for transforming currents for use with rectifiers.
According to this invention I form a magnetic circuit of the converter of a core
or cores Sheet 1, Figure 1, Sheet 2 Fig. 1, A. ends B and connecting bars C. The
central core is preferably circular and the coils P. S are of large diameter and of
flat section, Sheets 1 and 2.
I fix either the primary or secondary winding in one block on the centre of the
core or cores. The other coils either primary or secondary are suspended by
vertical rods R, Sheet 1, Figs. 1 & 2, above and below the fixed coils and there is
sufficient space left upon the core for these coils to be moved several inches up and
down. The movable coils hang clear of the core A and connecting bars C. The
vertical rods R which carry the coils P work in guides, but are not rigidly
connected to the coils. The movable coils are held by means of split metal
bands b, strapped round about the coils, the coils being made on their outer edge
of a conical shape so that they may be gripped and securely held by the bands
drawn tightly round them.
Each of the bands is split at three points Q, Fig. 3. enlarged view shown at
Sheet 1 Fig. 6, at which metal castings F are fastened on to the metal bands.
These castings are fixed together with screws, which are insulated from the band b
and fibre insulation H inserted between each section of the band. In order to
connect the bands supporting the coils with the vertical rods I make a flexible
coupling in 3 places as shown in Figs. 5 & 6 Sheet 1, in which E is a slot milled
out in the vertical rod and D is a screw with play in the vertical rod.
The movable coils above and below the fixed coils consist of about an equal
weight of copper winding and the mechanism is so arranged that the one set of
coils balances the other and also so that when the upper coils move away from the
fixed ones upwards the lower coils move away from the fixed coils downwards.
The three rods R above mentioned which support the upper coils are connected to
a metal star I. The 3 rods which support the lower coils are hung upon knife
edges K and beams J whose other ends are connected to the star I supporting the
upper coils.
The converter is so arranged that the tendency is for the coils to fall together
by the preponderance of the weight placed upon the star and this tendency is
counter-balanced by the repulsion of the movable coils from the centre coil when
the current flows.
The star I is guided and is formed with a cylinder, c, which fits on to a vertical
piston upon which it moves. This piston and cylinder act as a dashpot to prevent
any violent motion of the coils and so make the apparatus workable.

page_text: When the current flows in the coils a certain repulsion takes place, so long as
the current is normal the coils remain close together, if the current becomes too
strong the coils separate and the electromotive force is reduced and consequently
the current is diminished.
This
The converter is practically self-regulating, any additional regulation which is
required is done by means of adding or diminishing the weight on the star.
is done by having a lever connected to the star I by a link M, balanced on a
knife edge K². On this is placed a movable weight w. This can be conveniently
moved by hand. The exact current given by the apparatus being adjusted
according to the requirements by moving the weight backwards and forwards and
locking same with a screw S.
The irons of the end B and connecting side bars C I form of laminated sheet
iron pressed into heavy metal cheeks which keep the laminated iron in shape and
enable the machine to be mechanically fitted together, as shown in section marked C¹
Figure 3. Sheet 1.
The upper and lower castings B, also carry the supports for the knife edges of
the swing beams J and guides g, for the vertical rods R, which support the coils P.
Another method of construction is shown in Sheet 2 Figures 1, 2 & 3, in which
I use two circular or as nearly circular as possible vertical cores & connect them
with blocks B made of laminated iron sheets held in the same manner as already
described.
The magnetic circuit is then exactly like that of a Gramme ring without poles
but is rectangular in form. By this means I can wind coils P & S, of half the
diameter which it is otherwise necessary to use and use two for every one which
would be used on the before-described plan.
There are fixed coils S on each vertical core A and also movable coils P on each
vertical core.
This arrangement is a more economical one in the way of magnetic
circuit and of copper required, the coils under these circumstances being held rather
differently in the arrangement of bands and supporting rods, but the principle is in
both cases the same.
I use converters made in this way in connection with apparatus for rectifying
the direction of the current, namely for making alternating current into direct
Such apparatus I have described in my Patent No. 17,220 1891.
current.
In Figures 4, 5 & 6 Sheet 2 are shown different methods of arrangement of coils
which are equally applicable as the arrangement of coils described above. In each
case a different detailed arrangement of holding the coils is required, but on the
same principle as already described.
In certain cases I may place a condenser N Sheet Fig. in series with the
converter above described so as to counterbalance the self-induction of the apparatus
and reduce the apparent loss. The condenser also has the capacity of helping to
regulate the quantity of current which can flow.
In Fig. 4 Sheet 1, O is an alternator, N is a condenser, T is the self-regulating
converter, U is a rectifier, V is a circuit having inductive resistance on which work
is desired to be done.
The great object of this invention is to so build the converter and so shape the
coils that when working on full load the primary and secondary coils may be as
nearly co-incident, i.e., that they may be brought as close together to form a solid
mass as is mechanically possible so as to avoid a too great leakage of the magnetic
field when the converter is desired to give a large output. On the other hand
when it is desired to get a small output from the converter the coils must so
separate from each other that a complete leakage of the magnetic field takes place.
In order to accomplish this as above explained I prefer to make the coils of as
flat a section as possible so that when the primary and secondary coils are all
bunched together they approximate to a square section.
Another method, (shown at Sheet 2 Fig. 6,) of accomplishing the same result is
to wind say the primary coil P next to the central core and occupying a space equal
to half the length of the core and then wind a secondary coil S outside this, both

page_text: coils being clear of each other and of the central core, so that when the primary
moves up and the secondary moves down the two are end to end upon the core.
Another modification of this is (shown at Fig. 5 Sheet 2,) to wind the primary
coil close to the core and to fix it in the centre and to make the secondary coils in
two halves of a larger diameter so that when they are close together they envelop
the primary coil when they move apart they will occupy a place on the core clear
of the primary coil and considerable leakage will take place.
Again, (Fig. 4 Sheet 2) I may modify this arrangement by winding the primary
coil on the core, and of the section of a right angle triangle with its longest side to
the core, the secondaries are then wound in two separate coils which are of a right
angle triangle section with their longest side next to the side of the primary coil.
These coils are balanced and move up and down as above explained.
There are many obvious methods of carrying out the invention herein stated but
I have confined myself to describing those of greatest practical value.
In most cases it is immaterial whether the primary or secondary coils occupy the
position nearest to the centre core.
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 a constant current transformer in which regulation takes place by the
repulsion of movable coils, the use of a central fixed coil and two movable coils,
each of which recedes from opposite sides of the fixed coil.
2. In a constant current transformer the disposition of the movable coils in such
a manner that one movable coil balances the weight of the other movable coil and
a preponderating weight upon one coil tending to force the movable coils towards
the standing coil.
3. Self-regulating transformers in which the magnetic circuit is formed by two
cores and two yokes with movable and fixed coils on each core.
4. Self-regulating converters substantially as described and illustrated with
reference to Figures 1, 2 3 5 and 6. Sheet 1.
5. Electrical converters substantially as described and illustrated in Figures 1, 2
and 3 Sheet 2.
7. In supplying a constant current transformer with current from an alternating
source, the use of a condenser in series with the primary supply to nullify the
self-induction of the transformer so that the converter shall only take the same
number of apparent as true watts. Substantially as described and illustrated
Figure 4, Sheet 1.
8. The construction of self-regulating transformers in which the coils move
together and apart upon a circular and laminated magnetic core.
9. In constant current transformers varying the amount of the current produced
by adding to or diminishing the weight with which the coils are forced together or
by varying the position of a sliding weight upon the arm.
10. In constant current transformers the use of a dash pot to control the motion
of the coils.
11. The various details in the construction of self-regulating transformers
substantially as described.
Dated this Fourth day of October One thousand eight hundred and
S. Z. DE FERRANTI.