IMPROVEMENTS IN ARMATURES FOR DYNAMO ELECTRIC MACHINES & MOTORS
Year: 1885

page_text: I JAMES SWINBURNE. of 34 Holford Square London W.C., Electrician, do hereby
declare the nature of my invention for IMPROVEMENTS IN ARMATURES FOR DYNAMO
ELECTRIC MACHINES & MOTORS, to be as follows:―
In dynamos with iron in their armatures the currents in the wire of the
armature tend to magnetise the iron of the armature in a direction at right angles
to the field of the field magnets. Such armatures are generally in the form of
rings, drums or cylinders with the wire wound upon them. The designers of
dynamos, as a rule, seem to aim only at having as little resistance in the armature
as possible, and to overlook the prejudicial action of the current in the armature on
the iron of the armature; but according to the present invention this action may
be reduced. Take, for instance, the case of the Gramme ring, in the machine with
two poles. The wire inside the ring only cuts a few lines of force, & these it cuts
backwards. This part of the wire is, therefore, useless or worse, while it has full
action on the iron of the armature, as it is generally as close as possible to it. To
lessen this prejudicial action the wire may be kept off the iron inside by the
interposition of any nonmagnetic material. The wire on the outside of the ring
under the fieldmagnets is doing practically all the work, and the wire on the ring
which is passing from one pole piece to the other is not only useless resistance, but
is also acting prejudicially on the iron of the armature. It would be advisable to
cut this part of the armature circuit out if it could be done easily, but as that
demands a very complicated commutator, or else very few coils in the armature,
I according to my present invention annul the action on the armature. This I do
as follows:-Instead of joining the coils up consecutively as now done, I join a coil
which is under the influence of a field magnet in series with one not under the
influence, so that the current in the latter is reversed. By this arrangement the
current in all the coils under the influence of the field magnets is made to flow one
way, while currents in adjacent coils in that part of the ring which is not under
the influence of the field magnets is in different directions so as to neutralise the
effect on the iron. As a simple example suppose that the collector has 12 segments,
and that each field magnet embraces one third of the ring. The ring is wound
with 24 coils, and the circuit is as follows:-The end of coil 1 is joined to the end
of coil 8, the beginning of coil 8 to the beginning of coil 3; the end of coil 3 to
TD 077

page_text: the end of coil 10 and so on all round symmetrically. The segments come between
8 and 3, 10 and 5 & so on. The result is that under the field magnets the current
goes the same way in the adjacent coils, but in the other parts each coil neutralises
the action of its neighbour. Instead of the coils being separate the wires may be
mixed so as to neutralise one another's action more perfectly.
For simplicity the field magnets are here supposed to embrace one third each;
The armature may be arranged for any proportion, and may have any number of
pairs of coils; If the ring takes the form sometimes known as the cylinder the
arrangement is the same as with the ordinary ring. The armature I prefer is the
drun, in which the wire is all on the outside. Suppose that the field magnets
embrace one third of the armature as before, and that there are 24 spaces on the
outside of the drum, so that there are 12 coils and 12 segments in the collector.
Spaces 1 & 8 will be taken by one coil; 3 & 10 by the second, and so on all
round. The usual practice is to wind the coils into spaces diametrically opposite,
or opposite but one; this is very awkward as the wire has to be bent round the
shaft, thus preventing ventilation through the armature.
If the dynamo is large, the wire may take the form of rods. The drum armature
may then have rods on the. periphery, and the rods may be joined by plates of
stamped or cast metal. These plates may have lugs of suitable shape formed
thereon to make connections with the rods. The plates are preferably ring shaped
to allow a free path for the air to the inside of the armature. These plates may
be placed in layers of three, or of two with ventilating air spaces, or may be
arranged spirally like a winding stair. The joints may be arranged in series of
steps to allow them to clear.
If fine wire is used, the plate arrangement is too complicated, & so the wire is
wound over the ends. The chief difficulty is ventilation of the mass of wires at
the ends. To allow them to lie flat & to allow air passage a number, say 960,
outside wires may be arranged as follows to fit, say, a 48 part commutator. The
periphery is divided into 24 spaces & 12 coils are wound thus:-1 & 10, 3 & 12
& so on; there are thus 12 coils. Each is then divided into four making 48.
Of course 4 neighbouring segments then communicate with 4 coils in the same
angular position so that the armature is divided as to self induction as for 48 coils,
but as to angular position as for only 12 coils. To divide the armature angularly
for a 48 part commutator the 4 divisions of each of the 24 coils may be arranged
alternately with those of a neighbouring set at one side of the drum only. Thus
instead of 1 being wound over into 10 only it is wound partly into 11 & the coil
that would have fitted 11 is wound partly into 10. Thus 10 & 11 each contain
two of the 4 subdivisions of coil 1 & of coil 11 arranged alternately.
The correct angular positions are thus got without having the wires too deep on
the end of the armature, & ventilation through the armature is provided. Space 1
thus contains 4 sets of 10 wires with 4 connections to the commutator. Space 10
contains 2 sets of 10 belonging to space 1 & 2 belonging to 20. This arrangement
can be applied even when the coils are practically wound into opposite spaces as in
existing drum armatures, and may be modified for different numbers of coils.
TAL: 51
AT
1.
1000

page_text: Improvements in Armatures for Dynamo Electric Machines
and Motors.
I JAMES SWINBURNE of 34 Holford Square in the County of Middlesex,
Electrician do hereby declare the nature of my invention for IMPROVEMENTS IN
ARMATURES FOR DYNAMO ELECTRIC MACHINES AND MOTORS and in what manner
the same is to be performed, to be particularly described and ascertained in
and by the following statement:―
In dynamos with iron armature cores the currents in the armature wire tend to
magnetise the armature in a direction at right angles to the field due to the
magnets alone. The object of my invention is to lessen this action and to lessen
the tendency to heating in drum armatures. I accomplish this object by coupling
the wires on the armature so as to reduce the cross magnetisation, and in the drum
armature, to reduce the foucault currents also, and to provide free air space.
In the case of an armature of the Gramme type the wire inside the ring cuts
only a few lines of force, and cuts those backwards. The outside and some of the
end wire generates the electro-motive force, but all the wire acts on the armature,
producing what is commonly called distortion of the field. I lessen this distortion
as follows. Instead of joining the coils up consecutively in the way now usual,
I join up a coil that is under the influence of a field magnet in series with one not
under the influence of it, so that the current flows different ways in the coils.
The coupling is so arranged that the coils not under the fields have their currents
alternately in different directions, so that they have no action in cross magnetising
the armature. The system is best explained by diagrams.
The
Figure 1 is a diagram of a Gramme ring. The coil 1 is in series with coil 1',
2 with 2 &c so that the electric current is 1, 11, 2, 2¹ and so on.
The arrows
shew the direction of the current. The commutator segments come between 11
and 2, 21 and 3 and so on, so that with 24 coils there are 12 segments.
armature is shown symmetrical as to currents, but in practice of course there is
still some cross magnetisation due to the wire under the fields. It will be seen
that that part of the ring not under the field magnets has its currents alternately
in different directions. This winding is most applicable to large flat rings as
commonly used in the Schukert type of armature. The connections for a multi-
polar machine need no special description.
In drum armatures the cross magnetisation and self induction are less serious,
but my method of construction admits also of better ventilation.
Figure 2 is a diagram of a drum armature between field magnets ab It has
48 outside wires or 24 coils. Instead of coil 1 being wound from 1 over to 5¹ as
usual in a drum armature, it is wound to 11 2 to 2¹ and so on. Those wires with
the current going one way are black, those with it the other way are left white.
The alternate arrangement between the poles is thus shown clearly. For simplicity
of explanation each coil is made to occupy a third of the circle. In practice any
convenient proportion may be used.

page_text: Figure 3 is a diagram showing how this winding admits of ventilation of the
armature. The armature is made of discs in the form of rings strung on a spider c
fitted on the axle d. The armature thus resembles the well known Crompton
armature such as is illustrated in the specification of Letters Patent No. 4302
dated March 3 1884, except that no wires go through the centre and so more iron
is used, and the hole through is left just large enough to allow air to rush in to
ventilate the armature. Air spaces are left every inch or two along the armature
to allow a radial current of air outwards. The coils 1 11, 2 2¹ being wound as
shewn allow free access of air to the centre. If wound right across they would
foul the spindle and it would be difficult to admit any air. Figure 3 is a diagram
of a 12 coil armature, with 12 sections in the commutator. If it were wanted to
make a 48 coil armature, and the periphery of the drum were divided into 96 parts
the ends would be piled up too thick to allow good ventilation there. Thus if the
wire is one layer thick on the periphery it would pile up 20 thick on the ends.
To prevent this coils are wound in batches as in Figure 4. The coils 2, 3, 4 and 5
though forming one layer on the end of the drum are in different angular positions.
The commutator strips are made of different sizes to prevent sparking.
Figure 5 is a view of the end of a drum armature, the commutator being at the
other end. c, c are pins or pegs to hold the wire as it is wound. They may be
extracted after the armature is wound. d is a ring of metal to keep the wires
from covering part of the ventilating space e. f is the spindle.
These windings of small wire are to shew how high tension machines may be
wound, but the armature I prefer as an example of the use of my invention is a
low tension drum armature. In this case bars are used for wire on the outside
and plates make the connections across the ends of the armatures.
In Figures 6 and 7 g g are bars. On the ends of the armature piles of plates k
are fastened. One of these plates is shewn separately in figures 8 and 9. It is
made of stamped sheet copper with two connecting pieces h h fastened on.
Each
of these plates connects 2 bars across the end. The pieces h h are attached to
allow of good connection between a thick bar and a thin plate. A distance piece i
is put on the armature end first to allow clearance for the connecting pieces of the
first layer of plates.
The plates are laid on the ends of the armature so that the connections are step
wise, otherwise the connecting pieces h h would foul.
Figure 6 shews an armature end with two plates on and four bars connected
As the plates occupy more than a third of the circle the space may be left open
เ
for circulation of air or the plates may be arranged helically. m is the axle, n the
spider, and o ooo the air channels.
In figures 8 and 9 p is a tongue turned up to make a commutator connection.
The commutator strips may, however, be connected to g g direct Those plates are
held on by the screws r which are carefully insulated from the plates by a suitable
bush The plates are separated from one another by paraffined paper or other
suitable insulating material.
For very large currents thick bars, or broad strips are objectionable as they heat
(through foucault currents). Thus in figure 10 a strip as broad as 8 on the
periphery would get very hot. If split up as at uuuu the heating would not
be diminished if they were connected together at both ends, as shown by a strip t.
To avoid this heating I divide the bars up as shown at v w x y and za By. At
the commutator end these sets of bars are connected by a single plate, but at the
other they are separately connected. Thus v is connected to z, not to r; w to a
and so on.
The sum of the electromotive force of v and y is greater or less than
that of y and 2, but the sum of vand z is approximately equal to that of
and Y.
This method of coupling to avoid foucault currents is applicable when the coils
are connected right across the drum as well as when connected across a smaller
segment.
..
My invention is of course equally applicable to motors.

page_text: Having now particularly described and ascertained the nature of my said
Invention, and in what manner the same is to be performed, I declare that what
I claim is :-
1. In a Gramme or ring armature the method of arranging the connections of
the coils substantially as described in order to reduce the cross magnetisation of
the armature.
2. In a drum armature the methods of winding or arrangement of 'the wire
substantially as described and shewn in figures 23 and 4.
3. In a drum armature the method of connecting or arrangement of the con-
nections to rods across the ends by flat plates of the kind described, substantially
as set forth.
4. In a drum armature coupling a group of wires together at one end and
keeping them separate at the other end to avoid foucault currents substantially as
Bet forth.