Improvements in Direct Electric Current Transformers or Motor Generators.
Year: 1895

page_text: Date of Application, 21st Nov., 1895
Complete Specification Left, 21st Aug., 1896-Accepted, 10th Oct., 1896
PROVISIONAL SPECIFICATION.
Improvements in Direct Electric Current Transformers or Motor
Generators.
We, ALEXANDER BEWICKE BLACKBURN Manager of The Electric Construction
Company Limited and THOMAS LARGE BOYDEN of Wolverhampton in the County
of Stafford Assistant Engineer of the said company do hereby declare the nature
of this invention to be as follows:-
This invention relates to the class of electrical machines known as direct current
transformers or motor generators and consists in an improved construction of the
armatures of such machines whereby their efficiency is increased and the cost of
their manufacture is reduced. According to this invention the usual laminated
core is provided with slots at frequent intervals round the periphery and running
parallel with the axis of the said core, the said slots being preferably rectangular
or U shaped. Each slot carries a conductor or conductors of one set of the
windings, cach conductor being preferably of solid copper insulated and filling or
approximately filling the slot. The iron core is then wound with a layer, or layers,
of thin charcoal, iron, or steel, wire, or narrow tape of good magnetic permeability,
and preferably slightly insulated for example by oxidation varnish or the like.
This winding may be continuous, or it may be interrupted at intervals for the
purpose of clearing the usual driving horns, or projections, from the core to the
other windings not carried by the slots. When the said winding is continuous
the armature is provided with flanges at either end of the core and secured to the
shaft or core, upon the periphery of which flanges, projections or horns are formed
which are available to transmit the driving stress between the core and the
windings not carried by the slots. If preferred the armature conductors in the
slots may be in two portions, the lower portion in the slot being solid and
the upper or exterior portion being of stranded cable pressed into suitable shape.
When the slot winding has been completed as described the remaining winding,
or windings, covering the external surface of the core may be put on.
Dated this 21st day of November 1895.
JOHNSONS & WILLCOX,
47 Lincoln's Inn Fields, London, W.C., Agents.
Improvements in Direct Electric Current Transformers or Motor
Generators.
We, ALEXANDER BEWICKE BLACKBURN Manager of The Electric Construction
Company Limited of Wolverhampton in the County of Stafford, and, THOMAS
LARGE BOYDEN, Assistant Engineer of the said company, 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 the class of electrical machines known as direct current
transformers, or motor generators, and having a magnetic field common to two, or

page_text: more, armature windings, and consists in an improved construction of the armatures
of such machines, whereby their efficiency is increased, and the cost of their
manufacture is reduced.
wire or
In an arrangement according to this invention the laminated iron core which
carries the armature windings is provided with slots, or grooves, at frequent
intervals round its periphery, and parallel with its axis, the said slots, or grooves.
being preferably rectangular, or U shaped. Each slot, or groove, carries a
conductor, or conductors, of one set of the armature windings, each conductor, or
the conductors, being preferably of solid copper, suitably shaped and insulated so
as to fill or approximately fill the slot or groove. The said core is then wound
transversely to the conductors with a layer or layers of thin charcoal iron or steel
narrow tape of good magnetic permeability, and preferably slightly
insulated, for example by oxidation, varnish, or the like. This winding, which
forms a magnetic shield to the conductors in the slots, or grooves, may be
continuous from end to end of the core or it may be interrupted at intervals for
the purpose of clearing the usual driving horns, for the exterior winding, or
windings which are not in the slots or grooves. When the said winding is
continuous, and covers the whole of the curved surface of the core, the armature
may be provided with flanges at either end of the core and secured to the shait,
or core, upon the periphery of which flanges, projections, or horns, are formed
which are available to transmit the driving stress between the core and the windings
not carried by the slots, or grooves. If preferred the armature conductors in each
slot, or groove, may be in two portions, the inner portion being solid, and the
outward portion being of stranded cable pressed or formed into suitable shape,
both portions being united to the same end connector, which may be of any usual
form. When the slot winding has been completed, the remaining winding, or
windings, covering the external surface of the core may be put on.
In order that this invention may be fully understood we shall proceed more
particularly to describe the same and for that purpose shall refer to the accom-
panying drawings.
Figure 1 is a transverse section (on the line W X Figure 2) Figure 2 is a
longitudinal section, and Figure 3 is an enlarged detail of preferred form of
conductors according to this invention.
Two armature windings are here shewn as is usually the case; a is the laminated
core, and 6 are the slots, or grooves, round the periphery thereof and containing
the solid copper conductors of one of the armature windings. c is the iron, or
steel wire, or tape, encircling the entire winding, and forming a magnetic shield,
which decreases the loss due to Foucault currents in the solid conductors and
enables the whole of the available space in the slots to be filled with conducting
material; it also tends to promote silent running. When this wiring or taping is
completed, the core presents a smooth surface for the reception of the insulating
material between the two windings, with obvious advantages as regards the
soundness and durability of the insulation in a most vulnerable part of the machine.
d is the insulating material over the magnetic sheath on the cylindrical part of the
core. e shews a portion of the exterior winding which is the high tension portion
of the machine. This is preferably coil winding as in the Eickemeyer system, or
such as that described in the Specification of Letters Patent No. 5336 of 1895,
granted to us, where conductors are grouped together and wound in separate coils
which are afterwards slipped on the armature over the previously described low
tension winding.
Having now particularly described and ascertained the nature of our said inveu-
tion and in what manner the same is to be performed, we declare that what we
claim is :-
1. In an electric current transformer, or a motor generator, the arrangement of
a slot-wound armature having a layer or layers of fine iron or steel wire or tape of
good magnetic normes hilit

page_text: and the conductors in the slots, or grooves, with another set of windings not carried
in the slots, or grooves but arranged over the embedded conductors, and the wire,
or tape covering thereof; substantially as herein before described.
2. In an armature of an electric current transformer or a motor generator the
combination of a slotted or grooved core having conductors shaped so as to
approximately fill the slots or grooves with a magnetic sheath of iron or steel wire
or tape encircling the embedded conductors and with an independent set of
windings or coils overlaying the whole; substantially as hereinbefore described.
3. In an electric current transformer, or a motor generator, the arrangement of
armature wherein the low tension winding is carried in slots, or grooves, in the
core; and wherein each conductor consists of two portions, the outer portion being
of strand, and the inner portion being solid; as herein before described.
Dated this 21st day of August 1896.
JOHNSONS & WILLCOX,
47 Lincoln's Inn Fields, London, W.C., Agents.