Improvements in Alternate Current Transformers.
Year: 1890

page_text: Date of Application, 12th Mar., 1890
Complete Specification Left, 11th Dec., 1890-Accepted, 17th Jan., 1891
PROVISIONAL SPECIFICATION.
Improvements in Alternate Current Transformers.
Wo, GISBERT KAPP of Erba, Vinyard Hill Road, Wimbledon, Surrey, Electrical
Engineer WALTER CLAUDE JOHNSON and SAMUEL EDMUND PHILLIPS, both of
14 Union Court, Old Broad Street, in the City of London, Electrical Engineers,
do hereby declare the nature of this invention to be as follows:-
Our invention relates to alternate current transformers with closed iron circuit. In
the following description of our improvements we shall call that part of the iron
circuit of the transformer which is situated within the primary and secondary coils
"
the " core and that part of the magnetic circuit which is outside the coils we shall
دو
call the "yoke or "shell."
We form the core of a number of thin plates, by preference of rectangular form,
insulated from each other, and placed side by side, the number of plates, their
size and arrangement being such as to give the required cross sectional area, and
length of core. Upon this core we place a series of wire coils, all insulated from the
core and from each other, which coils form the primary and secondary circuits, and
are arranged in any suitable manner for this purpose; thus the 1st, 3rd, 5th, &c. coil
may belong to the primary circuit, while the 2nd, 4th, 6th &c. may belong to the
secondary circuit, or vice versa.
The ends of the core are made to project on either side beyond the coils, and we use
these projecting onds for making the magnetic joints with the yoke or shell.
The latter consists either of one or of two yoke rings formed of thin band iron
wound upon itself, with a strip of insulating material intervening between each
successive layer, so as to constitute a more or less rectangular ring, the opening of
which is just large enough to clear the coils. These rings rest with the flat surface
formed by the edges of their successive layers upon the flat surface formod by the
edges of the layers of the core, so that the edges in contact cross each other at or
about right angles, and in order to reduce the resistance of the magnetic joints thus
formed, we prefer to increase the thickness of the yoke ring at such parts by inserting
between the successive convolutions additional strips of insulating material. We may
employ either one yoke ring only, placed to one side of the core, in which case the
width of the yoke strip should be at least equal to the width of the core strip, or we
may employ two yoke rings, one on either side of the core, in which case the width
of each yoke strip should be not less than half the width of the core strip, but it might
be made more if a specially low magnetic resistance be required.
The core may also be formed of two sets of strips with a sheet of asbestos millboard
or other insulating medium between them, or the core and yokes may be otherwise
subdivided if the width of strip required in any particular size of transformer should
otherwise become inconveniently large. One method of doing this is by building up
a compound transformer containing several sets of cores and yokes. The core might
also be made either of cylindrical form, or with the top and bottom surfaces semi-
cylindrical, the yoke rings being in that case cut or otherwise shaped with a more or
less semicircular hollow to fit on the semicircular surfaces of the core, whereby an
increased surface would be afforded to the joints. With a view to still farther lessen
the resistance of the magnetic joints, we employ a cement composed of finely divided
iron, mixed with shellac or varnish, or other suitable substance with which the surfaces
of the joint are coated before being pressed together.
The above described improved constructions of transformers may be placed into a
cast iron or other suitable box, and the parts be held together by screws, wedges,

page_text: springs, or by other suitable means, the leads of the coils being brought through insulated
stuffing boxes in the sides of the box, which is closed by a watertight cover.
Dand this 10th day of Mb 1800
ABEL & IMRAY,
Agents for the Applicants.
14
COMPLETE SPECIFICATION.
Improvements in Alternate Current Transformers.
We, GISBERT KAPP of Erba, Vinyard Hill Road, Wimbledon, Surrey, Electrical
Engineer, WALTER CLAUDE JOHNSON and SAMUEL EDMUND PHILLIPS, both of
14 Union Court, Old Broad Street, in the City of London, Electrical 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
tstatement :-
Our invention relates to alternate current transformers with closed iron circuit.
In the following description of our improvements we shall call that part of the iron
circuit of the transformer which is situated within the primary and secondary coils,
the "core
"and that part of the magnetic circuit which is outside the coils we shall
call the yoke" or "shell."
We form the core of a number of thin plates, by preference of rectangular form,
insulated from each other and placed side by side, the number of plates, their size
and arrangement being such as to give the required cross-sectional-area; and length.
of core. Upon this-core-wo place a series of wire coils, all insulated from the core,
and from each other, which coils form the primary and secondary circuits, and are
arranged in any suitable manner for this purpose; thus the 1st, 3rd, 5th &c. coil
may belong to the primary circuit, while the 2nd, 4th, 6th &c. may belong to the
secondary circuit, or vice versa.
The ends of the core are made to project on either side beyond the coils, and we
use these projecting ends for making the magnetic joints with the yoke or shell.
".
The latter consists either of one or of two yoke rings formed of thin band iron
wound upon itself, with a strip of insulating material intervening between each
successive layer, so as to constitute a more or less rectangular ring, the opening of.
which is just large enough to clear the coils. These rings rest with the flat surface
formed by the edges of their successive layers upon the flat surface formed by the
edges of the layers of the core, so that the edges in contact cross each other at or
about.right angles, and in order to reduce the resistance of the magnetic joints thus
formed, we prefer to increase the thickness of the yoke ring at such parts by inserting
between the successive convolutions additional strips of insulating material. We
may employ either one yoko ring only, placed to one side of the core, in which case
the width of the yoke strip should be at least equal to the width of the core strip, or we
may employ two yoke rings, one on either side of the core, in which case the width
of each yoke strip should be not less than half the width of the core strip, but it
might be made more if a specially low magnetic resistance be required. The core
may also be formed of two sets of strips with a sheet of asbestos millboard or other
insulating mediam between them or the core and yokes may be otherwise subdivided
if the width of strip required in any particular size of transformer should otherwise
become inconveniently large. One method of doing this is by building up a com-
pound transformer containing several sets of cores and yokes. The core might also
be made either of cylindrical form, or with the top and bottom surfaces semicylindrical,
the yoke rings being in that case cut or otherwise shaped with a more or less semi-
circular hollow to fit on the semicircular surfaces of the core, whereby an increased
surface would be afforded to the joints. With a view to still further lessen the,
resistance of the magnetic joints, we employ a cement composed of finely divided iron,
mixed with shellac varnish, or other suitable substance with which the surfaces of
the joint are coated before being pressed together.
The above described improved constructions of 'transformers may be placed into a

page_text: cast iron or other suitable box, and the parts be held together by screws, wedges,
springs, or by other suitable means, the leads of the coils being brought through
insulated stuffing boxes in the sides of the box, which is closed by a watertight
cover.
To more fully explain the manner of carrying out our invention we will describe
the accompanying drawings in which
Fig. 1 represents a cross section and Fig. 2 a plan of one arrangement our
improved transformer.
Fig. 3 shews a perspective view of the core and yoke rings.
The lettering in all figures refers to the same parts.
a is the core, which we build up of thin soft iron plates as shown. Figs. 1 and 3.
bb are yoke rings made by winding soft iron strip upon a mandril or former of
suitable shape. Fig. 1 shows a cross section through the yoke rings, and Fig. 2 a
plan of them. The thick lines i and k in Figs. 1 and 3 represent sub-divisions of the
core formed by the interposition of sheets of insulating inaterial or otherwise. In
Fig. 2 the primary winding is represented by the coils marked c, and the secondary
winding by the coils marked d. The core with its winding and with the yokes is
placed in a box e provided with cover g, through which pass screws / pressing the
yokes and core securely together. The ends of the primary and secondary coils are
brought through insulating stuffing boxes f. Figs. 2 and 3 show that the horizontal
dimension of the yoke rings is increased at the places of contact with the projecting
ends of the core with a view to reduce the magnetic resistance of the joint.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed we declare that what wo
claim is :-
1. In a transformer with closed magnetic circuit; the combination of a straight
core composed of thin soft iron strip, with one or two ring-shaped yokes also
composed of thin soft iron strip, the core being laid across the yoke rings so that
the surfaces of the core strip and yoke strip cross at right angles or nearly at right
angles.
2. In a transformer with closed magnetic circuit the use of yokes made by winding
a continuous strip of soft iron to a ring shape, in combination with a straight core
laid diametrically across the yoke rings and insulated copper wire coils surrounding
the middle portion of the core, and surrounded by the corresponding portion of the
yoke rings.
3. The construction of transformer as herein described with reference to the
accompanying drawings.
Dated this 8th day of December 1890.
ABEL & IMRAY,
Agents for the Applicants.