Improvements in Electric Motors and Dynamo Machines.
Year: 1891

page_text: Date of Application, 29th Oct., 1891
Complete Specification Left, 29th July, 1892-Accepted, 28th Jan., 1893
PROVISIONAL SPECIFICATION.
Improvements in Electric Motors and Dynamo Machines.
HENRY CHITTY 13 Brackley Terrace Chiswick, Middlesex, Engineer, do
hereby declare the nature of this invention to be as follows :—
This invention has for its object the construction of electric motors, and dynamo
machines, in such manner as to obtain a regular or uniform rotary motion, from
the action of continuous, or approximately continuous electrical currents; or
vice versa.
The essential feature of the invention consists :-In a machine which has an even
number of magnets, or electro-magnets, arranged uniformly round a circle, forming
an even number of successive fields of alternating polarity, and which depends for
its action upon the difference between the number of its fields, and coils, or poles,
presented by its armature, in the reduction by the means herein set forth, of the
necessary difference between the number of fields and armature coils, or poles, to
the lowest possible limit, i.e. one, whereas in machines of present known construction
the limit is two.
The advantage gained by this improvement is great, as the armature coils, or
poles are made to occupy more favourable positions for combined action.
Combined with a field system of the character and arrangement as indicated
above is an armature composed of a number of bobbins of insulated wire wound
either upon iron, or upon non-magnetic cores, or preferably it may consist of a ring
built up in the usual way and divided by projections or cogs, into sections, which
are wound with insulated wire. The number of bobbins, or, in the case of a ring
armature, sections, is less, or greater than the number of fields, by one, or any
other odd number; and the bobbins, or sections have each two distinct windings in
opposite directions, the ends of the several coils being so connected together and to
a commutator, that the whole of the double series of windings form a closed circuit
going twice round the entire armature, the winding of each successive coil in this
circuit being in the contrary direction to the preceding one.
The following construction may serve to illustrate how a machine may be arranged
in the manner above described.
The field system which is secured to a suitable base may consist of a ring built
up of thin insulated, iron washers having 6 poles which project inwardly, dividing
the ring into as many equal parts. The 6 channels or spaces between the poles are
filled with insulated wire the winding and connections being arranged to produce
when joined to any source of electrical energy, successive poles of alternately N.
and S. polarity.
On a central axis is mounted an armature the core of which is also built up of
thin washers of iron, having 5 poles projecting outwardly just clearing the field
poles. In each of the 5 channels between the projections, is placed two distinct
windings arranged and connected as already described, the number of connections
being 10.
Mounted also upon the axis is a commutator, having (in this particular case,)
30 insulated contacts, arranged in 10 groups, each group containing 3 contacts
which are separated from each other by 9 intervening contacts of the several other
groups. From the wires connecting two successive coils, a connecting wire passes
to one of the groups of commutator segments, in such manner that the 10 connecting
wires to the successive coils are also connected to successive contacts and conse-
quently to the 10 successive contact groups of the commutator.

page_text: As there are 3 contacts in each group of commutator segments, either one, two,
or three pairs of brushes may be used.
The action of the machine is as follows.―
When an electric current is passed into the armature, through a brush, or
brushes, bearing upon a contact, or contacts of one of the groups of commutator
segments, it is divided into two equal parts, which flowing in opposite directions,
make each a complete circuit of the armature, when they are again united leaving
the armature by the other brush, or set of brushes; as the case may be.
The two parts, or branches of the current flowing in the two distinct windings,
will always be in one and the same direction in any one of the several armature
sections, but the direction of the current is reversed in successive sections, pro-
ducing alternately N. & S. poles at four of the armature projections, but in the
two successive sections by which the current enters, and leaves the armature, the
flow will be in the same direction, consequently the projection or pole between these
two coils, or sections, has no polarity. As the armature rotates, and the different
segments or groups of segments, pass under the brushes, the polarity of the armature
projections, will be successively neutralized, and reversed.
The brushes are arranged so that the armature poles are neutralized, just as they
come directly opposite the successive field poles. If when any armature pole is in
this neutral position, an imaginary line be supposed to pass through it, and the axis
of the machine, dividing the armature and fields equally, the poles on one side of
the line will be approaching fields of opposite signs to themselves, and those on the
other side will be receeding from fields of a similar sign.
To effect the reversing of the direction of rotation it is only necessary to arrange
the frame carrying the brushes, so that it may be shifted through an angle of 60°,
by these means the current may be reversed as regards the armature, without
affecting the fields.
. As before stated the above described arrangement, only serves as an example,
the construction of the machine being capable of considerable variation according
to the number of armature poles, and magnetic fields employed.
With a view to equalize or balance the mechanical effects of the current in the
machine, one, or more, pairs of armatures, constructed in the manner herein set
forth, may be arranged side by side upon the same axis, the poles of one armature
occupying intermediate positions relatively to those of the other of the same pair,
the coils composing the two armature circuits, being connected either in series or in
parallel, and in such manner that the neutral pole in one, is always diametrically
opposite to that of the other.
By dividing and arranging the armature as described at least three highly
important advantages are secured. 1. An equal balance of power, or torque.
2. A great reduction in the bulk, and weight, of field magnets. 3. The most
perfect ventilation, and means of getting rid of the heat, generated in the
armature.
The machine may be made automatically self-regulating in the following
manner.―
Two secondary brushes electrically connected together and to one of the primary
brushes, are so arranged that they both bear upon a contact, or that they bear
one upon each of two different contacts belonging to the same group of commutator
segments upon which, the primary brush to which they are connected is bearing;
or the two secondary brushes may take the place of one of the primary brushes.
In either case the two secondary brushes are so arranged that they may be separated
farther apart, both moving at the same rate their motion being controlled by a
governer suitably applied upon the axis of the machine, or in any other convenient
manner. By these means when the load is decreased and the speed of the machine
tends to increase in consequence, the governer acting upon the two brushes as
above described, causes them to embrace a larger number of commutator segments,
thus cutting out two or more of the coils in the closed eircuit, or circuits, of the

page_text: armature, or armatures, thereby reducing the power of the armature, or armatures,
and keeping down the speed.
تيمم
.
2001
HENRY CHITTY,
13, Brackley Terrace, Chiswick, W.
COMPLETE SPECIFICATION.
Improvements in Electric Motors and Dynamo Machines.
I, HENRY CHITTY, of 13 Brackley Terrace, Chiswick, Middlesex, 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 :-
According to this invention I construct a dynamo electric machine of the multi-
polar type, with an armature wound in such a manner that its action depends upon
the difference between the number of magnetic poles and the number of sections or
the number of what is hereinafter called "sets" of sections on the armature, this
difference being reduced to one.
The armature used may be of any suitable form, but I prefer to use a ring or
cylinder slotted or grooved to receive the conductors. In this way a very high
magnetic intensity may be produced in the air space without excessive magnetising
force, and at the same time the conductors are protected from mechanical injury.
If n be the number of magnet poles, I prefer to divide the armature winding
into nequidistant sections or into two or more groups of such number of equi-
distant sections, as hereinafter described. The n + 1 sections I define as a group
and the corresponding coils in the several groups I call a set.
It is generally advisable to have n such groups in combination, so that the total
number of sections will be n (n + 1), but any multiple, or submultiple of n groups
may be used as hereinafter described. If the number of groups is neither a
multiple, nor a submultiple of n the winding is unsymmetrical.
In consequence of the number of sections in a group being odd, each section
will consist of two coils which form the two halves of the winding, and between
which the full difference of potential exists. The sections in a group have each two
distinct windings in opposite directions-the ends of the several coils being so con-
nected together that the whole of the double series of windings form a closed
circuit going twice round the entire armature.
The use of an odd number of sections, presents the great advantage that the
E.M.F's of the whole number of sections in each group are added together, so
that the number of turns per section, is reduced to a minimum.
The different groups may be connected together in parallel by joining equi-
potential coils either in the winding, or at the commutator or by placing brushes
on each of the n neutral points (that is points which are centrally between adjacent
magnet poles) and connecting those which are equipotential, i.e. each alternate
brush. The latter method is preferable, as it is difficult to ensure exact equality
of E.M.F. in corresponding coils whilst the coils in any one group being distributed
round the whole circumference of the armature, the E.M.F. given by each group
is necessarily equal.
For connecting the groups in series all the corresponding coils in each group,
ie. the coils which constitute a "set" must be connected in series successively as
hereinafter described. In this case, only one pair of brushes is necessary but the
tendency to spark is diminished by placing a brush on every neutral point, alternate
brushes being connected together.
Various modifications of the above winding are possible, the groups being con-
nected in any combination of series parallel.
When it is desirable to have a greater number of sections than n (n + 1), the
space between each of the n (n± 1) sections may be subdivided by any convenient

page_text: number of sections which may be occupied either by distinct sets of coils connected
in parallel by the brushes, or by sets of coils connected successively in series with
the adjacent sets as hereinafter described.
To illustrate the above methods of winding a machine having 4 poles and
5 sections in each group may be taken.
Figure 1 shews four magnet poles A and a ring armature having a single group
of 5 sections. As before stated the coils are wound alternately in opposite
directions, and the winding makes two complete circuits of the armature, the end
of the last coil being finally connected to the beginning of the first.
The commutator consisting in this case of n (n + 1) segments, has 4 × 5=1
= 20,
of which 10 are connected to the coils on the armature, and cross-connected with
the remaining 10.
The commutator segments in general may be divided into
segments each, which is equivalent to saying that there are
points.
n
n
2
groups of 2 (n + 1)
equipotential neutral
The winding in Figure 1 shows coils 1 and 2 connected to segments 1 and 2 on
the commutator, whilst coils 3 and 4 are connected to segments 3' and 4' for the
sake of convenience instead of to 3 and 4, but the effect is the same since
segments 3 and 4 are cross-connected to segments 3' & 4'. In the same way while
coils 5 and la are connected to segments 5 and la, coils 2a and 3a are connected to
segments 2¹a and 3'a. Coil la is separated from coil 1 by insulation, shown at i and
similarly the other coils.
It will be seen that while each section is
1
-th of a circle in advance of
n±l
the last, the corresponding commutator segments succeed at intervals of
1
G-n 1) th=±
+
1
n(n±1)
th of a circle.
B are brushes bearing upon the commutator bars and conveying current to or
from them. This single winding has the objection that the current in the armature
distorts the field unsymmetrically so that the radial pull of the magnets on the
armature core is greater on one side of the axis of commutation than on the other
side, which causes a severe bending stress on the shaft. This may be modified by
having two armatures on the same shaft with windings at 180° as in Figure 2;
or it may be completely neutralised by combining the two windings on one armature
as shown in Figures 3 and 4.
The two groups may be connected together either in parallel or in serics.
Figure 3 shows the connection of two groups in parallel, in the example given
the cross connection of the commutator is dispensed with, the equipotential brushes
being connected instead. This winding is simply a duplication of Figure 1.
In Figure 4 the two groups are joined in series, which is effected by connecting
the corresponding coils of each group in succession. For instance starting from
segment 1 on the commutator the winding proceeds to coil a₁, then to b₁ touching at
segment 1' on the way, then to coil a, touching at segment 2, then to segment 2'
and coil b, and so on. The complete winding is not shown in this figure in order
that the way in which the winding proceeds may be more clearly seen. In this
case only one pair of brushes may be used but sparking is lessened by having the
full number.
n
In both these windings when is an even number it will be noticed that
commutation occurs in a north field (adjacent to a "north" magnet pole) and to
a south field alternately, and not simultaneously. This with coils threaded through
the ring as shown would produce an alternating induction round the ring, and so
greatly increase the tendency to spark. To avoid this either the brush must cover
:

page_text: two sections, or the commutator connections must be made to the central turns of
each coil instead of to the first or last.
The complete winding of n (n + 1) sections obviates all these difficulties.
Figure 5 shows all the groups connected in parallel. This case is a duplication of
Figure 3, intermediate coils being interposed between the adjacent coils constituting
the two previous groups and connected to the commutator in exactly the same way,
so that if each alternate section of Figure 5 were removed the winding shown in
Figure 3 would remain. Instead of connecting the two duplicate parts of
Figure 5 to the same commutator segment, each segment may be divided into two
halves which are connected to the corresponding coils of the two duplicate parts as
shown by dotted lines (Figure 5).
In this way all permanent connection between different groups is avoided and
the groups are connected by the brushes only. All danger of short-circuiting, due
to difference of E.M.F. in the coils under different field poles is thus obviated.
It will be noticed that by this method of connecting to the commutator the short-
circuiting of the coils is accomplished by the two commutator segments con-
nected to the coil being joined in some cases by a single brush, and in others
by two equipotential brushes and their connecting bar. There are of course
other methods of connection whereby this would be modified.
Figure 6 illustrates the complete winding in series. The course of the con-
ductor is as follows:-The windings of alternate coils are in opposite directions as
indicated by the full and dotted lines.
Starting from segment. it passes to sections a, and b₁ segment 1' sections o
and d, then to segment 2 sections a, and b, segment 21 section (, and d. then to
segment 3 sections a, and b. Segment 3' section c and d and so on till all the
sections are half filled, then d, is connected to a' (i.e. in this example, the upper
half of a₁) and segment la₁ then :-
Segment la sections α and b¹ segment 1³a sections and d₁¹
"
2a
За
,,
"
"
1
a² and b₂¹
a₁₁ and b₁¹
"
2¹a
3¹a
"
"
"
c,¹ and d¹
c₁³ and d¹
I
and so on until d¹ is joined to the beginning of a₁ which completes the winding.
It will be seen that in this way the short circuiting of a "set" of coils that is a
corresponding coil in each of the several groups is effected simultaneously. The
short-circuiting of any set say a b c d₁ can be effected by a single brush joining
segments and 2, but the tendency to spark is diminished by having 1' and 2¹ also
joined by an equipotential brush, so that when being commutated 1, 2, 1¹ and 2¹
are all connected together.
In cases where it is required to have a greater number of sections than n (n + 1)
any multiple of that number may be used, with a corresponding increase in the
number of commutator segments. Figure 7 shows an example of 2 n (n + 1) sections,
but any other multiple might be used.
The winding is as follows:-
1-2
"
» α-d, and b₁₂
11-2¹
""
"
h−b, and d₁–c,
"
"
Aug
and b,
2¹
"
وو
c, and d
and so on.
Where the number of slots in the armature is already great, it may be advisable
to increase the number of commutator segments only. If for example the number
of segments is made double the number of slots, each coil may only fill of each
alot, the other being added after the completion of the set and connected to the
next adjacent set of commutator segments. The segments in this case will not
exactly correspond with the position of the slots, being a little displaced, but if
the number of slots is large, the effect of this will be negligible.
Figure 8 is a diagram view of a machine having 8 magnet poles and 72 sections
in the armature.

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 :-
66
―
1. In a dynamo-electric machine of the multi-polar type, of an armature winding
in which the number of equally spaced sections, or what has herein been called
"
sets of sections is greater or less by one than the number of field poles. The
number of sections comprising a set being equal to the number of field poles, or to
any submultiple thereof, so that a "set "of sections consists of sections equally
spaced and similarly situated with regard to different field poles.
2. A dynamo electric machine constructed as in Claim 1 and with intermediate
sets interposed in the spaces between the n (n + 1) sections and connected in series
or parallel as herein before described.
3. The use in combination with a dynamo electric machine of the kind described
in the first claim of a commutator so connected that all the coils of any set are
commutated simultaneously.
4. The construction of dynamo electric machines of the multipolar type substan-
tially in the manner herein before described.
11
ليوم