Improvements in Cores for Converters and for other Electrical Apparatus.
Year: 1890

page_text: Date of Application, 2nd Apr., 1890
Complete Specification Left, 31st Dec., 1890-Accepted, 7th Mar.. 1891
TRUVIDIONAL SPECIFICATION.
Improvements in Cores for Converters and for other Electrical
Apparatus.
-
Partly communicated from abroad by THE WESTINGHOUSE ELECTRIC COMPANY,
of Pittsburgh, Pennsylvania, United States of America.
I, REGINALD Belfield, of 4, Victoria Mansions, in the City of Westminster,
Electrical Engineer; do hereby declare the nature of this invention to be as
follows:-
This invention has for its object the manufacture of laminated cores for con-
verters and other electrical apparatus in such manner as to make them as effective
as possible, and at the same time cheap in construction.
These cores have hitherto been.made of soft iron, and the purer this soft iron is
the more perfect the core becomes.
The Westinghouse Electric Co. of Pittsburgh has found that, contrary to what
is generally understood, mild steel, such as that made in the Siemens furnace or in
the Bessemer converter, especially with the basic process, is, with certain pre-
cautions in the manufacture, superior to ordinary soft iron for this purpose. It is
found, however, that manganese has a deleterious effect, if therefore this mild steel
is made in the Besseiner converter, the oxidation is not carried to the usual extent,
and Spiegeleisén, poor in manganese and less in quantity than that usually employed,
is used so as to get a mild steel formed of iron practically free of all impurities
except a little carbon. This is cast into ingots and rolled into plates and sheets in
the usual manner. The lamina are cut from these sheets. This mild soft-stee!
possesses considerable advantages over the ordinary soft iron used for like purposes
for, while it increases the efficiency of the apparatus, it is also very pliable and is
extremely useful for cutting plates, as for instance for armatures of converters
which are required to each form a closed magnetic circuit, yet be opened to admit
the coils. These pliable converter plates can be formed of a variety of shapes so
as to form these closed magnetic circuits.
Hitherto these circuits have been formed by E-shaped plates on the plan set forth
in Patent No.. 9728 of 1887, or with or without the wings set forth in that Patent,
and with or without a plate filling up the space at the ends of the E plates through
which the core has been passed. Theoretically the best plate is one having no
break as shown in Figure 1 set forth in the enclosed drawings. The best plate
hitherto made has been the E-winged plates mentioned in the aforesaid Patent
Specification. The difficulty of using the plates theoretically perfect, such as is
set forth in Figure 1, is, that it is impossible to get the core into them, and the
only way these plates can be used would be by threading the core through them all,
and in fact winding the core in place, an utterly impracticable plan, as the only
easy method of making transmitters is to wind the coil or coils separately first, and
then place the plates in position.
Now I have invented various inodifications of this plate 1 or its equivalent, which
have advantages differing from those of the E-shaped plate set forth in the afore-
said Specification. It practically consists in cutting the plates in any way of the
numerous points set forth in dotted lines in Figure 1, in the drawing, but in as few
as possible and thus forming other shapes than the E-shaped plates already men-
tioned. Figures 2, 3, 4, 5, 6, 7 and 8 are illustrations of these, and of course it is
obvious that in several of these cases it can be further modified by cutting the end
pieces in the centre as in Figure 10, instead of at one end, just as the centre piece is
Cut in the centre in Figures 2 and 7, also that instead of cuts parallel to the sides,
the cuts can be oblique as set forth in Figure 8 or as set forth in Figure 4 of the

page_text: Specification I have already alluded to. Figure 9 shows a very simple form, there
being only a single cut through the centre division. Again, in place of making
the two pieces to butt one against the other, a part of each can be cut away as set
forth in Figures 11 and 12. This is better than shaping them to a point, as they
are less liable to get out of shape on this plan than where the pieces are shaved off
from the level to a sharp edge, and the continuity in this case is more perfect than
where the plates are butt-jointed. Figures 13 and 14 show a modification by
which the two parts, formed, either with butt-joints as set forth in Figures 2 to 9,
or lap joints as set forth in Figures 11 and 12, swivel on a common pin d. They
can thus all be placed in position and attached together before ever the core is
inserted. In the drawing, a a, b b represent the coils respectively primary and
secondary or it may consist of only one coil, and c c' represents the plates all strung
on an iron wire d, and placed between the coils.
To complete the magnetic circuit, plates c are turned round in the direction shown
by the arrows e, and the plates c¹ are bent over in the direction shown by the
arrows e', and thus they encircle the coils in the manner shown by the dotted
lines.
thin 1nt
SA1 1900
COMPLETE SPECIFICATION.
Improvements in Cores for Converters and for other Electrical
Apparatus.
Partly communicated from abroad by THE WESTINGHOUSE ELECTRIC COMPANY,
of Pittsburgh, Pennsylvania, United States of America.
I, REGINALD BELFIELD, of 4, Victoria Mansions, in the City of Westminster,
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 the manufacture of laminated cores for converters
and other electrical apparatus in such a manner as to make them as effective as
possible and at the saine time cheap in construction.
These cores have hitherto been made of soft iron and the purer this soft iron is the
more perfect the core becomes.
The Westinghouse Electric Company of Pittsburgh has found that, contrary to
what is generally understood, mild steel such as that made in the Siemens furnace
or in the Bessemer converter, especially with the basic process has with certain pre-
cautions in the manufacture, superior advantages over ordinary soft iron for this
purpose. These advantages may be due partially to the purity of the metal thus
obtained and partially to the molecular structure of the soft steel, which is believed
to be more dense than that of commercial soft iron.
The process may be said to consist generally in first obtaining a good quality of
iron and subjecting this.to a process such for instance as the Bessemer process_or_
the so-called basic process, whereby_the_carbon-and-other impurities are actively
burned out, by causing oxygen to permeate the entire mass while in a heated
condition and in this manner the metal is reduced as pure as practicable. In
treating by the Bessemer process an excess of oxygen is supplied to the molten mass
and this forms an oxide which is less magnetizable than the pure metal. Moreover
if the metal is allowed to cool immediately after the reduction by the oxygen it is
brittle and hard to work. A certain amount of manganese is therefore added.
This takes up the excess of oxygen and renders the iron ductile. The presence of
any considerable amount of manganese is however objectionable, as it lessens
greatly the magnetic quality of the iron, therefore it is desirable that as little
manganese as possible should be employed.

page_text: The metal may be prepared by the basic process and a very nearly pure metal
practically free from the oxide obtained. The open hearth process is especially
suited to the purpose, as the metal may be frequently tested and a very pure product
obtained. In either instance however the product is better adapted to the
requirements than any of the forms of commercial soft iron.
After the steel has been produced, it is cast into ingots and rolled into sheets.
It is desirable that during this process the metal should be thoroughly worked and
rendered dense in structure and readily susceptible to magnetic influences. After
the ingots are rolled into thin sheets, plates of the proper form and size are stamped
from the sheets according to the particular form of core in the construction of which
they are to be employed. The plates are then annealed thoroughly for the purpose
of removing whatever temper may remain in them and also for forming an oxide
upon the surface and edges including the burrs which may be formed by the
stamping process. Such oxide serves to separate the plates from each other when
built into cores.
Hitherto these cores when intended for transformers have been generally formed
by E-shaped plates such as on the plan set forth in Patent No. 9728 of 1887, with
or without the wings set forth in that Patent and with or without a plate filling up
the space at the ends of the E-plates through which the core has been passed.
Theoretically the best plate is one having no break as shown in Figure 1 set forth
in the drawings filed with my Provisional Specification. The best plate hitherto
made has been the E-winged plates mentioned in the aforesaid Patent Specification.
The difficulty of using the plates theoretically perfect, such as is set forth in
Figure 1, is, that it is impossible to get the coil or coils into them, and the only way
these plates could be used would be by threading the coil through them all, and in
fact winding the coil in place, an utterly impracticable plan, as the only easy method
of making transformers is to wind the coil or coils separately first, and then place
the plates in position.
Now I have invented various modifications of this plate 1 or its equivalent which
have advantages differing from those of the E-shaped plate set forth in the
aforesaid Specification.
Figure 2 shows a form of plate which gives great facilities in building up, the
coil being first wound after which the core of magnetic material is built up over
then in the manner described in the before mentioned Specification No. 9728/87,
having the plates arranged so as to break joints as described in the above
Specification.
Figures 3 to 7 show modifications of this plate the plates being cut so as to
facilitate the building up of the transformer.
Figure 8 shows a plate a modification of Figure 4. This plate has diagonal cuts
at the corner.
Figure 9 shows a modification of Figure 2. It is of course obvious that in
several of the above cases the shape can be further modified by cutting the end
pieces in the centre as in Figure 10 instead of at one end just as the centre piece
is cut in the centre in Figures 2 and 7. Also that instead of cuts parallel to sides
the cuts can be oblique as set forth in Figure 8 or as set forth in Figure 4 of the
Specification above alluded to. In place of making the two pieces to butt one against
the other, a part of each can be cut away or stamped in a press so as to form a
shoulder. This gives a larger amount of surface in contact without lessening the
amount of magnetic material.
This is also applicable to the above figures either at the corners as illustrated in
Figures 11 and 12, or at the centres, ends or sides as shown in Figure 10, in which
the centre tongue is shown to be overlapping. Figures 13 and 14 show a modifica-
tion by which the two parts are formed either with a butt joint as set forth in
Figures 2 to 9 or lap joints as set forth in Figures 11 and 12. These two parts
swivel on a coinion pin D, they can all be placed in position and attached together
before ever the coil is in place as shown in Figure 13; the coil or coils is then

page_text: placed in position, the arms are swung round according to the dotted lines, when
they take up a position shown in Figure 13 by dotted lines encircling the coils.
Having now particularly described and ascertained the nature of the said inven-
tion, as communicated to me by my foreign correspondents, and in what manner the
same is to be performed, I declare that what I claim is :-
1. The manufacture, of laminated cores of electrical instruments from mild steel*
of the character substantially as described.
2. The improvements in or re lating to form of plates for the cores of electrical
converters substantially as herein described.
Dated his 21st day of December 1890
REGINALD BELFIELD.