Improvements in Dynamo Electric Machines.
Year: 1896

page_text: Date of Application, 17th June, 1896
Complete Specification Left, 17th Mar, 1897-Accepted. 17th July, 1897
PROVISIONAL SPECIFICATION.
Improvements in Dynamo Electric Machines.
I, WILLIAM MORRIS MORDEY, of Redholm, Loughborough, in the County of
Leicester, Electrician, do hereby declare the nature of this invention to be as
follows:-
This invention has for its object improvements in dynamos, and relates particularly
to the removal, in a simple and inexpensive way, of the difficulties caused by
sparking and armature reaction met with in machines having armature windings
sunk in slots or holes in the armature core, especially when armatures so constructed
are used with a small clearance of air space between the armature and the poles of
the field magnet.
In such inachines the armature reaction is considerable, and the output is greatly
reduced by the sparking at the brushes and the necessity for a large forward lead.
The following is a description of a Gramme dynamo constructed according to my
invention. The armature is preferably made with slots or holes at the outer surface.
The coils are wound in the usual way, the number of turns for any given E.M.F. being
substantially the same as in the ordinary armature, but instead of connecting the
consecutive coils in series, each coil is joined to another coil situated a certain distance
away on the armature core, these two coils so separated being treated as a single coil
so far as connection to the commutator is concerned. Small auxiliary poles may be
used between the ordinary poles, placed so as to act on the forward coil of each of the
pairs of coils.
This arrangement enables sparkless collection to be made without forward lead, or
with a backward lead, and secures the economy of power, and of material resulting
from the use of a small air gap.
Improvements
Dynamo Electric
I, WILLIAM MORRIS MORDEY, of Redholm, Loughborough, in the County of
Leicester, Electrician, 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 improvements in dynamos, and relates particularly
to the removal, in a simple and inexpensive way, of the difficulties caused by sparking

page_text: and armature reaction, which difficulties are most pronounced in machines having
armature windings sunk in slots or holes in the armature core, especially when armatures
so constructed are used with a small clearance or air space between the
armature and the poles of the field magnet. In such machines, the armature reaction
is considerable, and the output is greatly reduced by the sparking at the brushes, and
the necessity for a large forward lead.
The following is a description of a Gramme dynamo constructed according to my
invention. The armature is, preferably, made with slots or holes at the outer
surface. The coils are wound in the usual way, the number of turns for any
given E.M.F. (electro motive force) being substantially the same as in the ordinary
armature; but, instead of connecting the consecutive coils in series (as is usual in a
Gramme winding) each coil is joined to another coil, situated a certain distance away
on the armature coil, these two coils so separated being treated as a single coil so far
as connection to the commutator is concerned, as I shall now proceed to explain by
reference to the accompanying drawings, wherein Fig. 1 shows (diagrammatically) in
end elevation, part of a Gramme dynamo with armature coils arranged according to
my invention.
. 1 is the armature core, formed at its outer surface or periphery with slots 2 in each
of which, and around the core, are wound two armature coils, 3, 3, (although there
might be one coil only in each slot, the number of slots being then doubled).
For the sake of clearness I indicate only seven coils. At A there are two coils 3,3";
at B come the next two coils 3, 3; at G are other two coils 3, 3. It is to be
noted that the distance between the coil 3 at A and the coil 3* at G is, according to
my invention, equal or approximately equal to the distance or gap D between the tips
of the adjacent poles N.S. The parts being thus arranged, the connections of the
coils are as follows-One end of the coil 3 located at A is in communication with one
segment (or sector) 4 of the commutator; the other end of the same coil 3 is connected,
by a conductor 3b, to one end of the coil 3* located at G. The other end of this last
mentioned coil 3* is connected, by a conductor 3c, to that end of the coil 3 located
at B which communicates with the commutator segment 4°. All the coils of the
armature are to be connected, according to the method just above explained. Each
connected pair of coils 3, 3ª constitutes one element of the whole winding.
It will be seen that, with this connection of the coils, the current and E.M.F. are
in the same direction, in each connected pair of coils or element, during the greater part
of each half revolution; but that, as the element, comes into the region of
commutation, its two connected parts have generated in them opposing electro-motive
forces, due to the fact that, whilst one part is under the tip or end of one pole piece,
the other part is under the tip or end of the next following pole piece, of opposite
polarity. In this way I am enabled to collect in an active part of the field without
sparking, and with a smaller forward lead of the brushes 6 than is usual, or with no
lead of the brushes, or even with a backward lead thereof, thereby enabling me to
obtain the economy of power and of material that result from the use of a small air
gap. The actual collecting position is determined by the relation as to number of
turns, or of angular position, or both, of the connected portions of each
element.
Fig. 2 is a developed plan view showing, diagrammatically, a greater number of
elements than Fig 1, and also illustrating the relation of the elements to each other,
to the field magnet poles N S (shown in dotted lines), to the interpolar gap, and to
the commutator segments, some of which are shewn at 4, 4*.
Figs. 3, 4, 5, 6, and 7 show five successive positions of one element of the
winding.
In these diagrammatic views the slots (shown at 2 in Fig. 1) are omitted, in order
to simplify the drawing. The small arrows indicate how the electro-motive forces,
in the two coils constituting this one element assist one another in the positions
represented in Figs. 3 and 7-that is to say, during the greater part of the revolution;
and how, in the position represented in Fig. 5, the said forces oppose one another.
The act of commutation should occur just when, or a very short interval of time after,

page_text: the position represented in Fig. 5 is attained. Figs. 4 and 6 shew two intermediate
positions of the element.
By way of further elucidation, I will now compare an example of my arrangement
with an ordinary Gramme arrangement having the same number of turns or
convolutions. I select for this comparison, an ordinary Gramme ring in which there
are 420 turns or convolutions grouped as 70 successive elements of 6 turns or
convolutions each, furnished with a Commutator having 70 segments or bars; the
beginning of each element of the winding being connected to one segment of the
commutator, and the end of such element being connected to the next adjacent
segment of the commutator. Now, according to my invention, this same Gramme
ring would be modified in its disposition as follows. Each element of 6 convolutions
would be separated into two coils, ench of three convolutions, the second of the coils
would be wound on the ring at a certain distance from the first (along the ring) as
hereinbefore fully described; but the whole six convolutions would still be joined in
series between two adjacent segments of the comminutator; there would still be
70 segments in the commutator, and 420 convolutions, in total, around the ring.
I may use a larger or smaller number of slots in proportion to the coils than are
shown in the drawings and referred to in the foregoing description. For example I
may have only one turn in each slot, or I may have several turns, or, on the other
band, I may distribute the portions of each element over several slots, without
departing from the spirit of my invention.
Auxiliary poles may be used between the ordinary pole tips, so arranged as regards
position and polarity as to produce in one coil or portion of each element, passing
through the region between the pole tips, an E.M.F. similar to that produced by one
of the poles.
The polarity to be given to ench auxiliary pole for a Grammne armature should be
the reverse of that for a drum.
Fig. 8 is a diagrammatic illustration of such an arrangement as applied in a
machine of Gramme type. N.S. are the ordinary poles and A is an auxiliary pole
placed between the tips of the two poles N.S.
In such an arrangement, the gap d together with the relative number of turns in
the portions 3 and 3 of each element, determines the distance apart of the coils 3,3*
of each element. The auxiliary pole A in this case should have S polarity and in the
next succeeding space the auxiliary pole should have N polarity, assuming that
commutation takes place approximately in the position shown in Figure 8 and with a
right handed direction of rotation of the armature. In a drum dynamo A should
have the reverse polarity to that for a Gramme because the separate portions of the
element should be under the influence of similar polarities at the time of commutation.
It is to be understood that Fig. 8 shows only the auxiliary pole between one pair of
pole tips, the space or spaces between the other pole tips being provided with
auxiliary poles having the same order as regards polarity. The auxiliary poles are
conveniently magnetised by a winding in connection with the ordinary field winding,
preferably by a shunt winding, to give an initial magnetisation and by a series
winding to increase or maintain the magnetisation as the load increases, after the
manner of a compound wound field magnet.
In applying my invention in multipolar machines, whether with series or parallel
winding, I space the winding so that the electro-motive forces in any one element of
the winding oppose one another during the moment of commutation but aid one
another during the greater part of the revolution.
My improvements are applicable to dynamos whether used as generators or
as motors.
I know that it has been proposed to use in conjunction with a smooth armature a
method of coupling according to which, at the time of commutation, a coil under the
influence of a field magnet would be in series with one not then under such influence,
the arrangement being such that the current would flow in different ways in the
coils, and the object aimed at being to lessen the cross magnetising effect; the

page_text: arrangement in question however was not only different from mine but furthermore
it would not give the same result as mine.
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. In a dynamo electric machine the arrangement of each element of the
armature winding as a pair of coils or separate portions so disposed and connected
that during the greater part of the revolution the electro-motive forces in the two
coils or the separate portions are additive, while at the time of commutation they are
in opposition.
2. In the armature of a gramme dynamo electric machine having twice as many
coils as there are segments of the commutator, and in which the said coils are joined
to in series, thus forming pairs each of which pairs constitutes one element of the
winding, the disposition in which the angular breadth or spacing between the two
coils constituting each element is equal or approximately equal to the angular breadth
or spacing between the edges of two adjacent poles of the field magnet.
3. In the armature of a dynamo electric machine of the type referred to in Claim 2,
the disposition in which the angular breadth or spacing between the two coils
constituting each element of the armature winding is equal or approximately equal
to the angular breadth or spacing between the edge of one pole and an adjacent
auxiliary pole of the field magnet.
4. In a dynamo electric machine an armature comprising a core made with slots or
recesses and armature coils arranged within the said slots or recesses and disposed
and connected in the manner referred to in Claim 1, substantially as described.
1007
W. M. MORDEY.
W. Lloyd Wise, C.P.A.,
46 Lincoln's Inn Fields, Agent for the Applicant.