Improvements in Dynamo Electric Machines and Electric Motors.
Year: 1888

page_text: Date of Application, 18th Dec., 1888
Complete Specification Left, 18th Oct., 1889-Accepted, 14th Dec., 1889
PROVISIONAL SPECIFICATION.
Improvements in Dynamo Electric Machines and Electric Motors.
I, JAMES YATE JOHNSON of 47 Lincolns Inn Fields in the County of Middlesex.
Gentleman do hereby declare the nature of this Invention which has been com-
municated to me from abroad by Charles S. Bradley of Yonkers in the County of
Westchester and State of New York in the United States of America Electrical
Engineer to be as follows:-
This Invention relates to certain improvements in the construction and operation of
dynamo electric machines and electric motors which improvements are more.
particularly intended for application to machines of the class having more than two
poles in the field magnet such class being generally known by the name of
"multipolar." In the application of ordinary rules of construction to multipolar
machines in which the reversals of magnetism are frequent the local currents are
produced in the windings even when the latter are of comparatively small wire and.
when the winding consists of bars or large wires these eddying or local currents
become a serious detriment to the efficiency of the machine. These eddying or
parasitical currents are mostly due to the fact that one side of the conductor passes
into the magnetic field before the other side, so that an electro motive force is
developed on one side of the conductor while no electro motive force or a less electro
motive force is being developed on the other side, and hence two sides of the conductor
form a closed circuit in which a local current is generated every time the bar enters
and every time it emerges from the field and the result is a large quantity of heat is
set up in the machine and its current capacity thereby reduced. For the purpose of
overcoming this difficulty the armature core is, according to this Invention constructed
so that it reaches out so as to almost touch the pole-pieces and the copper conductors
or windings are sunk in grooves formed lengthwise in the periphery of the core such
grooves being of greater depth than width and the grooves of less width than the:
intervening projections of iron which stand between groove and groove. By this
construction a machine is produced in which the magnetic circuits are as nearly
complete and unbroken as possible, the only break being the small clearance necessary
for the rotation of the armature. By properly proportioning the iron ribs left between
the grooves on the iron drum of the armature eddying or local currents, in the bars
can be to a large extent prevented.
A feature of this invention lies in the armature winding the same being composed
of insulated conductors laid in the herein before described grooves and end connectors
joining such conductors in pairs in rectangles in combination with a multipolar field magnet
system presenting opposite polarities to the respective sides of each of such rectangles.
A further feature of this invention is the combination with the conductors on the
armature of bifurcated connectors adapted to span across the end of the armature
between the respective sides of each of the rectangles which constitute the continuous
closed circuit of the armature whereby heavy bars which are sometimes used for
machines of large current capacity can be readily connected into the required closed
circuit in a simple and inexpensive manner and at the same time prevent excessive
waste of energy which would be due to a high resistance if the conductors of the
armature were connected in any of the well known ways.
A further feature of the present invention is the construction of the field
magnet as a whole the same consisting preferably of two-annular cast or wrought iron
yokes forming the end frames and binding the cores of the energizing coils together
and of these cores it is preferred to use six or a greater number the same being
ymmetrically disposed and having inwardly projecting pole-pieces at their middle
portions and the energizing coils at either end next the yokes. Each core carries at

page_text: its centre a laminated pole-piece made up of a number of wrought iron plates slipped
on to the core and prevented from turning thereon by a spline on the core and a notch
in each plate. Before placing the field magnet cores in position their energizing coils
are previously made ready and simply slipped into place after which the entire field
magnet is inserted between the end yokes and bolted firmly in position. It is preferred
to so proportion each of the polar faces as to make it cover as many ribs of the
armature as will equal in their combined section the section of the two cores which
energize the said pole-piece so that all lines of force emanating from a pole-piece are
transmitted through the iron of the armature to the two adjacent poles of opposite
polarity. The diameter of the yokes is such as to afford an opening through which
the armature may be readily inserted and withdrawn.
The bearings for the armature shaft are mounted on brackets which it is preferred
to make of non-magnetic metal and these are bolted to the end yoke. The journal
boxes are formed with a spherical enlargement at the centre and these are adjusted by
means of a double cone-fitting adjustably arranged in the brackets so that the wear
of the boxes may be taken up in a symmetrical manner from time to time and at
the same time the boxes are free to adapt themselves to perfect alignment with the
shaft.
The armature core is constructed of a number of thin sheet iron plates stamped
out to the required form to produce the grooved periphery and these plates are
slipped over a sleeve adapted to fit the shaft having a head at one end and a nut
the other end and between these two the mass of thin plates is clamped and
compressed by means of two moderately heavy end plates. It is preferred to
insulate the sheets of thin wrought iron by paper enamel varnish or otherwise.
Each of the grooves in the periphery of the armature can receive two insulated
conductors which it is preferred to place one on top of the other, both bars
projecting beyond the armature core at the ends, but the outer bars extending
beyond the inner bars to afford access for connection by means of the bifurcated
end connectors and by using these connectors in the proper manner the entire
circuit is made symmetrical and the two halves of the armature when divided into
multiple circuit by the attachment of the brushes will be exactly equal in their
generative capacity or the rise of potential if the generator and in the fall of potential
if the motor.
A further feature of this invention is the commutator which is composed of the
usual circular range of parallel metallic bars insulated from each other and held upon
the shaft by suitable attachments. A special feature according to this Invention is
however an annular sleeve fitted on the shaft by means of inwardly projecting shells
alapted to clamp the shaft or be otherwise attached thereto. This sleeve is slit
circumferentially at a number of points without destroying its radial strength. This
slitting is important in machines carrying a heavy current as it breaks up to a very
great extent the eddy currents which are induced in the sleeve, if the latter be
continuous by the currents traversing the commutator bars, and loss of energy
and one source of annoying heat in the commutator are thus avoided. It is
preferred to make the slits more numerous towards the armature end of the
commutator.
When the armature is held fast on the shaft and the bifurcated connectors are all
fixed to their respective commutator bars the commutator needs no key or set-screw
as the connectors are heavy and act as bracers in both directions to retain the
commutator rigidly in one position. A further function is performed by these
connectors. In arinatures of that type wherein the conductor is composed of bars
with bar to bar connections at the ends, it is highly important to have such connections
of the lowest possible resistance. Hitherto designers have been content with making
the sectional area of such connectors nearly or quite as large as the area of the bar.
This Invention goes further and effects two results; namely the reduction of the
resistance due to the connectors and the avoidance of loss of energy in the armature
conductor proper due to rise of temperature which, if not prevented would cause
an, increase of resistance. For these purposes the connectors are made of considerable

page_text: greater sectional area than the bars and being of copper like the bars they have
greater conductivity for heat. Hence any tendency to a rise in the temperature is
checked by the superior heat conductivity of the connectors which carry off all such
heat from the bar ends and therefore the increase of resistance in the bars by heating
does not take place to any material extent and the armature remains cool during a
long run. This has an important bearing on the regulation of potential in the low
resistance machines. The connectors besides having greater sectional area are also of
much greater surface and are exposed to the air directly and therefore radiate what-
ever heat they receive from the bars and thus they are themselves prevented from
experiencing a rise of temperature.
Dated this 18th day of December 1888
J. H. JOHNSON & Co.,
Agents.
COMPLETE SPECIFICATION.
Improvements in Dynamo Electric Machines and Electric Motors.:
I, JAMES YATE JOHNSON of 47 Lincolns Inn Fields in the County of Middlesex,
Gentleman do hereby declare the nature of this Invention (which has been communi-
cated to me from abroad by Charles S. Bradley of Yonkers in the County of
Westchester and State of New York in the United States of America Electrical
Engineer) and in what manner the same is to be performed to be particularly described
and ascertained in and by the following statement :-
In dynamo machines it has been found that where the reversals are very frequent
eddying or local currents are produced in the windings, even when they are of
comparatively small wire, and when the winding consists of bars or large wires these
eddying or local currents become so serious as to impair the efficiency of the machine.
These eddying or local currents are due to the fact that one side of the conductor
passes into the magnetic field before the other side, so that some of the "lines of
force" pass through one side of the conductor while none or a less number of lines of
force are passing through the other side, so that an electro-motive force is developed
on one side of the conductor while no electro-motive force or less electro-motive
force is being developed on the other side, and thus the two sides of the conductor
form a closed circuit in which a local current is generated every time the bar enters
and every time it emerges from the field. Although this electro-motive force is
produced for only a very short period of time, yet the resistance of this local circuit
is so extremely low that a great strength of current is developed, and the consequence
is that the conductor soon becomes heated in this way, and its safe carrying capacity
for current which is supplied to the external circuit is thereby reduced. These
eddying currents are produced to some extent in the ordinary two-pole machine, where
the width of the bars or windings is comparatively great; but they become very
much greater in the multipolar machines, because the number of reversals or the
number of times that the bar enters and leaves the magnetic field is increased in
proportion to the number of poles, and consequently the eddying currents are
produced with corresponding frequency during each revolution of the armature.
.
One of the objects of this invention is to reduce these eddying or local currents
and construct the machine in such a way that the armature-winding may be
composed of very much larger wires or conductors than has heretofore been
possible, without any loss either of efficiency or of capacity from this cause.
Another object of this invention is to produce a machine in which the magnetic
circuits are as nearly complete as possible, the clearance necessary for the rotation of
the armature being the only break in the continuity of the magnetic circuits, and which
circuits are practically uniform or of the same magnetic capacity throughout, and at the
same time furnishing a large mass of iron to concentrate and direct the lines of force,
thus producing powerful magnetic action with a small amount of copper and iron and
extremely small expenditure of energy in the field, because the magnetic circuit
has the smallest possible break, and at the same time increasing the strength of

page_text: the magnetic field, and consequently the electro-motive force, and also permitting
the use of larger conductors in the armature without reducing its magnetic
capacity.
To accomplish these results, the armature-core is constructed so that it reaches out
to the faces of the pole-pieces and entirely fills the cylindrical armature-space,
whereby the armature-core is.as nearly in contact with the pole-pieces as is practicable
for its rotation, and the copper conductors or windings are sunk in grooves formed
lengthwise in the periphery of the core. By properly proportioning the projecting
iron ribs left between the grooves on the iron drum eddying or local currents in the
bars are to a large extent prevented.
In the accompanying drawings, Figure 1 represents an end view of this machine,
showing the multipolar field. Figure 2 is a longitudinal section of the armature.
Figure 3 is a detail end view of the armature, shewing a few of the commutator-
connections and style of winding outlined. Figure 4 is a detail view of one of the
commutator-connectors. Figure 5 is a modified arrangement of conductors in the
grooves. Figure 6 is an end view of an armature with winding and commutator,
showing connections; Figure 1 is a longitudinal vertical section of the complete
machine in modified form the section being taken through the centre. Figure 2* is
an end elevation of sane, the armature not showing the winding. Figuro 3* is a
transverse vertical section through the pole-pieces. Figure 4* is a longitudinal
vertical section of the commutator. Figure 5 is a transverse section of the same.
Figure 6 is a perspective showing the improved connectors used.
In Figure 1, A represents the field, which is shown in the form of a six-pole
multipolar field. B represents the armature. The armature-core C, which may be
built up of laminae or thin discs in the ordinary way, to prevent the generation of
Foucault currents, is made so as to fit as nearly as possible the cylindrical space
within the pole-pieces, only sufficient space between the two being left for proper
clearance of rotation. In the convex surface of the iron drum or core C thus formed
are cut grooves D D D. &c., the number of these grooves and their shape depending
upon the size of the machine and other conditions.
;
The armature shown is provided with seventy four equidistant grooves, which are
preferably made wedge-shaped, so that the two sides of the intervening iron pieces
are parallel, and consequently the cross-section of this iron portion is the same at all
depths, or, at least, as small at the periphery as it is within but of course the slots
may be made of any desired shape. The proper depth for these slots depends upon
the strength of current to be permitted in the machine; but in all cases it seems
essential to have these slots or grooves of very much greater depth than width, and
the ribs left standing between them of much greater height than thickness, in order
to properly carry out the principles of the invention. Each slot may be provided
with a single bar, or, if more electro-motive force is required, two bars, or any
number of bars or wires may be placed in each slot.
In Figures 3 and 6 two bars are arranged in each slot. These copper bars are
drawn of trapezoidal form, one to fit the bottom part of the slot and the other the
top part, the bottom one being enough wider or deeper than the top one, in order to
have the same area in cross section, and they can be conveniently insulated from each
other and the iron core by mica insulation. In order to connect the copper bars with
each other in succession and with the commutator, a very convenient and efficient
means of connection is provided. This consists of copper Y-shaped connecting-
pieces E, stamped or otherwise cut from a single sheet or strip of copper and bent
into the form shown in Figure 4. The straight ends of these connectors E, are
'connected in any convenient way with the commutator strips F-by letting them into
slots, for example and the forked ends are respectively connected with such outer
and inner bars as are to be connected together, the outer bars projecting at the ends
of the armature beyond the inner bars, as shown in Figure 2, so as to permit the
connectors to be put in place without interfering with each other, as will clearly be
understood from Figures 1, 2, and 4. At the other end of the armature the bars
are connected in the proper way by a similar set of connectors, the only difference

page_text: being that this set of connectors has no inwardly-projecting portions to connect with
the commutator.
The whole scheine of winding is clearly illustrated in Figure 6, which shows the
grooved armature with two superposed bars laid in each of the grooves D, the outer
bars overhanging at the ends, as shown in Figure 2, the commutator F, while the
six-pole field is represented in dotted lines. Each of the bars is numbered, and the
numbers from 1 upward are given to the bars in the order of their connection. The
connectors E between bars at the commutator end are represented by heavy black
lines, and the connectors between bars at the opposite end of the armature are
designated by thinner lines. By following these connections it will be seen that,
starting from the negative brush in one direction, the circuit is back through bar 1,
across the rear, forward through bar 2, across the front and back through bar 3,
across the rear and forward through bar 4, across the front and back through
bar 5, across the rear and forward through bar 6, thence to bar 7, and so on around
and around until finally it comes forward through bar 148 and unites by a connector
with bar 1, making a complete closed circuit, which is then thrown into multiple by
placing the brushes at an angle of either sixty degrees or one hundred and eighty.
degrees, according to convenience of access. The entire winding therefore constitutes
a series of rectangles, the two principal sides of each of which are in this case
substantially sixty degrees apart, and hence at a given moment receive the inductive
effect at two points of the path of imaginary rotation, both inductive effects being in
a common direction in the rectangle considered as a circuit, and therefore
accumulative. Under such conditions of winding and the relations of it with the
iron of the armature and field-magnet there is practically no distortion of the magnetic
circuit by the current in the armature-conductor.
The distance between the consecutive slots in the armature-core in this machine
should be such that, retaining as a factor the length of the armature and pole-piece,
the aggregate cross-section of the iron or the magnetic carrying capacity of the
armature-core at one time under each pole-piece should be sufficient to carry all the
magnetism developed by the field core or cores which energize each pole-piece. In
other words, the cross-sectional area of all the ribs under any pole-piece is at least
equal to that of the field-magnet core or cores energizing that pole-piece, so that all
the lines of force will be carried by the iron of the armature core and none will pass
through the copper bars or winding.
By this method of proportioning the ribs, so that their magnetic capacity shall be
at least equal to that of the core or cores m, energizing the inducing-poles p, and
such carrying capacity is fully preserved to the full depth of the ribs and undiminished
by undercutting, the possibility of eddy-currents in the conductors and of magnetic
short circuit from rib to rib is greatly reduced; and this is true independently of the
depth of the grooves D, so long as enough ungrooved iron is retained in the armature-
body to carry the total induced magnetism. Suppose, for instance, each pole-piece is
energized jointly by two cores each of seven square inches sectional area, making. a
total of fourteen square inches. If the thickness of each armature-rib be one-fourth
inch and eight ribs lie under the pole-piece at once, there will be a total rib
thickness of two inches. Hence if the pole-piece and the armature-body are each
made seven inches long the total surface of the ribs under that pole-piece will be
fourteen square inches, and the ribs will carry all the magnetism that can be induced
in that pole-piece. Obviously the lengths of the pole-piece and armature-core become
an essential factor in the proportioning of the sizes and relations.
Upon consideration of this construction of machine it will be found that not only
is the capacity of the magnetic circuits greatly increased and the electro-motive force
of the machine thereby raised and at the same time the amount of energy required to
charge the field is very greatly reduced, but that the current capacity of the machine can
be indefinitely increased, and without affecting the electro-motive force, by increasing
the depth of these grooves, which hold the bars or winding, the only effect of
increasing the depth of these slots being the slightly increased length of the magnetic
circuit or path through which the magnetism passes.

page_text: Figures 1 to 6 show a modified six-pole machine, the field magnets of which are
constructed in the following manner. At each end is a heavy cast or wrought iron
yoke, A', in the form of a ring, and between these are bolted in a circular range
equidistant apart the six magnet cores B'. Each core carries at its centre a laminated
pole-piece C, made up of a number of wrought-iron plates c', slipped onto the core
and prevented from turning thereon by a spline on the core and a notch in each plate.
The coils D' are then slipped on the remaining portions of the cores B₁ and the whole
retained firmly in position by bolting the yoke-rings A¹ in place. Each polar face
should be so proportioned as to cover as many ribs of the armature as will equal in
their combined section the section of the two cores which energize the said pole-piece,
and hence all lines of force emanating from a pole-piece are transmitted through the
iron of the armature to the two adjacent poles of opposite polarity. The inside
diameter of the yoke-rings A', is such as to afford an opening through which the
armature may be readily inserted and withdrawn.
The end brackets E, carry the self-adjusting bearings for the shaft F', upon which
the armature is mounted. The journal boxes g¹ g₁ are formed spherical at their
centre, as indicated by ', and the two balves g1 g of each box are finished by
sweating them together, boring and facing, and then separating and facing off the
adjacent edges, so that when the two boxes are placed on the shaft they will not quite
come together, and are kept true by suitable liners placed between their edges. Each
of the brackets E¹ has a conical central opening, which freely passes the ends of the
boxes g' g', but bears against their spherical surface h', which surface is held on the
opposite side by the follower-plate 2, having a similar opening at its centre. Bolts
serve to draw these two conical faces against the sphere h¹, and thus hold the journal-
boxes g g against rotation or end motion.
To facilitate the centreing and setting, an annulus, m¹, is formed on each
bracket E, closely fitting the follower plates i¹. Obviously by this construction the
wear on the boxes gl can be always taken up without in the least disturbing the true
axial position of the shaft F¹, and hence the armature will always be perfectly central
in the field.
An additional advantage lies in the ability to set the parting-line of the boxes at
any angle, so that the pull of the belt may be always arranged in proper relation to
the boxes. The armature is constructed as follows; A sleeve n' having flange o¹ at
one end, is fitted to the shaft F¹. Before placing it in position a metal head pl is
first placed on the sleeve n' then a number of sheets of thin wrought-iron r¹, insulated
by paper, enamel, varnish, or otherwise are slipped over the sleeve finishing with a
metal head q', similar to p', the whole mass being then closely clamped together by
the. nat s¹, screwing on the threaded end of sleeve n', as shown. The periphery
of the armature is longitudinally grooved, as shown. Each groove receives two
insulated conductor-bars (marked, respectively u' and v₁₁) preferably placed one on
top of the other, as indicated, both bars projecting beyond the armature-core at the
ends, but the outer bars, u', extending beyond the inner bars to afford access for
connection. The bar ¹ under one pole is to be connected to a bar v¹, under the next
pole, and so on. To effect this, a blank having the body w¹ and the arms y' y' is
stamped out of a sheet of thick copper. The arms y y are pressed to such angle as
to exactly reach the required distance, and each is again at its extremity bifurcated
and so bent as to embrace the ends of the conductor-bars with an elastic pressure,
after which they are soldered or otherwise permanently connected. Should this
connection at any time get loose, the conductivity will still remain safe on account of
the elastic pressure.
At the commutator end the connector-body w¹ extends downwards for connection
to the commutator-bars. These bars a¹ may be held in any of the well-known ways:
in the drawing two shrinkage-bands 1, are shewn clamping them on to an annular
sleeve c³, fitted on the shaft by the inward extending shell. The sleeve c³ is slitted
circumferentially at a number of points without destroying its radial strength. This
slitting is important in machines carrying a heavy current, as it breaks up to a very
great extent the cddy-currents which are induced in the sleeve c by the current

page_text: traversing the bars a¹, and thus loss of energy and one source of annoying heat in the
commutator are avoided. These slits are preferably more numerous toward the
armature end of the commutator.
When the armature is held fast on the shaft and the connectors w¹ y' are all fixel
to their respective commutator-bars, the commutator needs no key or set-screw, as the
connectors are heavy and act as braces in both directions to retain the commutator
rigidly in one position. In armatures of that type wherein the conductor is composed
of bars with bar-to-bar connections at the ends it is highly important to have such
connections of the lowest possible resistance. Hitherto designers have been content
with making the sectional area of such connectors nearly or quite as large as the area
of the bars whereas by constructing them according to this invention the following
results are obtained namely the reduction of the resistance due to the connectors, and
the avoidance of loss of energy in the armature-conductor proper, due to rise of
temperature, which, if not prevented, would cause an increase of resistance. The
connectors according to this invention are made of considerably greater sectional
area than the bars, and, being of copper, like the bars, they have greater conductivity
for heat; hence any tendency to a rise in temperature is checked by the superior
heat conductivity of the conductors, which carry off all such heat from the bar
ends, and therefore the increase of resistance in the bars by heating does not take
place to any material or observable extent, and the armature remains cool during a
long run. The connectors, besides having greater sectional area, are also of much
greater surface and are exposed to the air, and therefore radiate whatever heat
they receive from the bars, and thus they are themselves prevented from experiencing
a rise of temperature.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed I declare that what
I claim is :-
1. An iron armature having longitudinal peripheral grooves of greater depth than
width, with intervening iron ribs, and insulated conductors laid in said grooves in
combination with field-magnets and pole-pieces, the proportions between armature,
field magnet cores, and pole-pieces being such, substantially as described, that the
ribs under any pole-piece are at least equal in combined magnetic capacity to tl
core or cores of the field-magnet energizing said pole-piece.
2. An armature composed of an iron core having longitudinal peripheral grooves,
insulated conductors laid in said grooves, and end connections joining said conductors
in pairs in rectangles, in combination with a multipolar field-magnet system presenting
opposite polarities to the respective sides of each such rectangles, substantially as
described.
3. In an armature having its conductors or windings connected in predetermined
rectangles spanning several sections of winding, the combination, with the conductors,
of the bifurcatod connectors E, substantially as described.
4. The combination of the solid iron core B¹ and pole-piece C³, made up of a
number of iron plates, c', occupying planes at right angles to the axis of said
core, and each plate perforated to receive said core within its periphery, substantially
as described.
5. In an armature, the combination, with the conductors thereof, of the metallic
bifurcated connectors, each fork being slotted to receive one of said conductors and
uniting in a body portion adapted to connection with the commutator, substantially as
set forth.
6. In an armature, the connector composed of the body to' and the forks y'y', all
in one piece, said forks y' y being bent apart to reach two different parts of the
armature circumference, and each slitted at its outer end and bent to spring over the
armaturo-conductors.
7. The combination, with a bar-commutator, of an internal metallic sleeve, or
shell insulated from the bars of the commutator and slitted circumferentially,
substantially as described.

page_text: 8. In a bar-armature, the combination, with the bars, of bifurcated end commutators
having greater heat conducting and radiating capacity than said bars, substantially as
described.
9. In a bar-armature, the combination, with the bars, of bifurcated end connectors
of greater sectional area than the bars and having their surfaces exposed directly to
the air, substantially as set forth.
10. In a bar-armature, the combination, with the bars, of bifurcated end connectors
having greater electrical conductivity per unit of length than said bars, substantially
as described.
J. H. JOHNSON & Co.,
Agents.