Improvements in Dynamo Electric Machines and Motors.
Year: 1891

page_text: Date of Application, 29th Sept., 1891
Complete Specification Left, 28th July, 1892-Arcepted, 29th Sept., 1892
PROVISIONAL SPECIFICATION.
.Improvements in Dynamo Electric Machines and Motors.
I, WILLIAM BROOKS SAYERS, of Glenwood, Bearsden, near Glasgow, in the
County of Dumbarton, Electrical Engineer, do hereby declare the nature of this
invention to be as follows:-
This invention has reference to an improved construction of armature for dynamo-
electric machines and motors in which the connections between the armature
winding and the commutator are so arranged that they will cut part or all of the
useful lines of force of the magnetic field as they revolve, the object being to
obtain a sparkless or nearly sparkless collection at the commutator under conditions
where this would not be possible, if the ordinary direct method of connection
between the armature winding and commutator were adopted.
For this purpose instead of making the connections between the armature winding
and commutator sections in the ordinary manner, I wind these connections (herein-
after called the commutator coils) around the armature core in such a direction and
in such a position relatively to the position of the armature coils to which they are
connected, that the E.M.Fs. induced in them and the armature coil which forms a
connection through the two commutator coils concerned at any time shall tend to
neutralize one another, if one of the said commutator coils is under the pole piece,
and the other not, at the moment when the brush connects the two sections of the
commutator. The winding is so designed that the resultant E.M.F. shall be just
sufficient to reverse the current in the armature coil and to reduce the current in the
commutator coil to zero at the moment when it is leaving the brush. By this means
there is obtained a sparkless break.
The commutator coils may be wound over the top or by the side of the armature
coils to which they are connected, or they may be led around the circumference of
the armature any desired angular distance before being led round the core, so that
a backward or forward lead, as may be required, can be given to these coils
relatively to the armature coils, and they may be led either a fraction of a turn or
any number of turns around the armature core as may be necessary to secure the
desired result.
By my invention the brushes can be set with a backward lead instead of with a
forward lead as is usual. By this means the effect of the current flowing through
the two sections or series of armature coils situate for the time being between the
pole pieces of the field magnet, is to aid the field excitation with the result that
instead of an increase in the armature current tending to reduce the E.M.F.
generated as is the case with simple shunt machines running with a forward lead,
the armature current tends to increase the magnet flux and consequently to increase
the E.M.F. generated. To secure this result in machines for parallel working
it has hitherto been necessary to resort to compound winding of the field coils.
As the strength of the trailing corner of the pole piece increases with the
armature current, the brushes will require little or no moving, the E.M.F. required
to effect the reversal of the current in the coils during commutation being
automatically increased as required by the increase in the strength of said pole
piece.
When the dynamo or motor is required to run in either direction, and the
commutator coils have a lead relatively to the armature coils as hereinbefore
mentioned, I employ two independent commutators and two sets of commutator
coils and give the set of commutator coils connected with one commutator a lead in
one direction and those connected with the other commutator an equal lead in the
opposite direction. One commutator will then be used when the machine is

page_text: running in one direction, and the other when the machine is running in the
opposite direction, the brushes being lifted off the commutator which is not
in use.
Dated this 29th day of September 1891.
W. LLOYD WISE,
Per F. J. Brougham,
46, Lincoln's Inn Fields, London, W.C., Agent for the Applicant.
COMPLETE SPECIFICATION.
Improvements in Dynamo Electric Machines and Motors.
I, WILLIAM BROOKS SAYERS, of Glenwood, Bearsden, near Glasgow, in the
County of Dumbarton, Electrical 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 :-
This invention has reference to improvements in dynamo electric machines and
motors of the kind in which the commutator strips are connected to the sections of
the armature winding through commutator coils in which an electro-motive force
is set up when the machine is running the object being to obtain a sparkless or
nearly sparkless collection at the commutator under conditions where this would not
be possible if the ordinary direct method of connection between the armature
winding and commutator were adopted, that is to say, where the commutator
brushes have a backward lead when running as a generator and a forward lead
when running as a moter.
For this purpose according to my invention each of the said commutator coils is
connected to the armature winding in such a manner that it will have a backward
lead with reference to the point between sections of the armature winding to which
it is connected, when the machine is running as a generator, and a forward lead
when the machine is running as a motor, and the commutator brushes are arranged
so as to have a backward lead when the machine is running as a generator and a
forward lead when it is running as a motor, the arrangement in each case being
such that the armature current will tend to increase the total magnetic flux, and
that the resultant E.M.F. induced in any two of the commutator coils and in-the
section of the armature winding that connects them will reverse or tend to reverse
the current in the said section of the armature winding and reduce to zero the
current in the commutator coil connected to the commutator strip that is about to
leave the commutator brush at the time when one of the said two commutator coils
is under one of the horns of the field magnet poles that is strengthened by the
armature current and the other has passed from under the same and the two
corresponding strips of the commutator are connected by a commutator brush.
The commutator coils may be wound over the top or by the side of the armature
coils to which they are connected, or they may be led around the circumference
of the armature any desired angular distance before being led around the core, and
they may be led either a fraction of a turn or any number of turns around the
armature core as may be necessary to secure the desired result.
My invention may be applied to dynamo electric machines of various types.
In the accompanying drawings
Fig. 1 is a diagrammatic view illustrating its application to a dynamo electric
machine with ring armature.
Fig. 2 is a perspective view illustrating its application to a dynamo electric
machine with drum armature.
Fig. 3 is a diagrammatic representation of field magnets and armature
suitable for use with my invention when no winding is used upon the field
magnets.
Referring to Fio. 1 A A is the main
DI R
D

page_text: and B'— B³— B³— are commutator coils according to this invention wound around
the armature core. The former set are connected at one of their ends to the
arinature winding A at the points D1 D2 D3 respectively, and at their other ends
to the commutator sections E' E' E' respectively. The latter set of commutator
coils are connected at one of their ends to the armature winding at the
points D₁ D, D, respectively, and at their other ends to the commutator
sections E, E, E, respectively. Each commutator coil is connected to the armature
winding at a point in advance of the coil, with reference to direction of rotation
of the armature, when running as a generator, or to a point which would be in
rear of the coil if the armature should be run in the opposite direction as a motor.
F and F are the commutator brushes. N. S. are field magnet poles.
Assuming that the armature is rotated in the direction of the arrow 1 and is
running as a generator, then the direction of the current through the armature
winding and the respective commutator coils when the same are in the positions
shewn, will be that indicated by the arrows on the said winding and coils. At this
time the armature current is mainly passing through the commutator coil B₁+ to
the central commutator section E¹ under the brush F+ and from the brush F-
through the commutator section E, to the commutator coil B¹-; the current
flowing through the commutator coils B2+ and B2- in advance of the coils B'+
and B and which are respectively connected to the commutator sections E
and E, that are about to leave the tips of the brushes, is approaching zero under
the effect of the greater E.M.F. which is being generated in the commutator
coils B'+ and B' in consequence of the latter coils being under the tips N* S*
of the pole pieces NS; and a current is commencing to flow through the com-
mutator coils B³+ and B³- connected to the commutator sections E3 and E, that
are just coming under the brushes in consequence of the E.M.F. generated in them
being approximately equal to that in the coils 13+ and B'- which are carrying
the bulk of the current. As the armature advances forward the commutator
coils B+ and B₁- will leave the tips N* S* of the pole pieces N S and the
E.M.F. generated in them will rapidly fall in consequence, while the portions of
the armature coil which are connected between them and the commutator
coils B+ B will also be well away from the tips of the pole pieces and will be
comparatively inactive. The commutator coils B+ and 'B' will however be
approaching the tips N*S* of the pole pieces where the magnetic flux is densest,
and as a consequence if the proportions of the armature coils to the commutator
coils are correct, the current in the portions of the armature coil A connected
between B+ B¹— and B³+ B³— respectively will be reversed and that in the
commutator coils B'+ B' will be brought down to zero just as the sections E' E
to which they are connected are leaving the tips of the commutator brushes and
a sparkless break will be the result.
The two arrows N' S₁ passing through the armature indicate the direction of
magnetisation which would be produced by the field coils alone. The arrows N' S'
indicate the direction of magnetisation and position of the poles which would be
produced by the current in the armature coils if the commutation took place in
the ordinary way by brushes having a lead in the direction of rotation. The
arrows N S indicate the direction and approximate position of poles when the
brushes are set with a backward lead and the machine is running as a generator,
which is rendered practicable by my invention. From this it follows that whercas
in the former case the current in the two sections of the armature coils situated for
the time being between the pole pieces of the field magnet is opposite to the
direction of field excitation; in the latter case the effect of the current flowing
through the said two sections or series of armature coils is to aid the field
excitation, with the result that instead of an increase in the armature current
tending to reduce the E.M.F. generated as in the case with simple shunt
machines running with a forward lead in the ordinary manner, the armature current
tends to increase the magnetic flux and consequently to increase the E.M.F.
generated. To secure that increased electro motive force shall be caused by an

page_text: increase of current in the armature or main circuit in dynamo machines for
parallel working, it has hitherto been necessary to resort to compound winding of the
field coils.
Furthermore as the strength of the trailing corner of the pole piece when
running as a generator, or the leading corner when running as a motor, increases
with the armature current, the brushes will require little or no adjustment, the
E. M.F. required to effect the reversal of the current in the coils during commu-
tation, being automatically increased as required, by the increase in the strength
of the said pole piece.
In the arrangement shown in Fig. 2 the main or armature winding A is wound
upon the well known Hefner Von Alteneck principle, in 48 sections of two turns
each on an armature core of the drum type. The slots C in this armature core
are cut deeply and the first half of the winding wound in the bottom thereof, the
second half following next while the commutator coils occupy the upper portions
of the slots.
A portion of one of the commutator coils B is shewn broken away, and a
junction, with the insulation stripped off, between the main armature winding and
a commutator coil is shewn at D. It will be seen from this figure that each of the
commutator coils passes near one end into the slot second removed, in the direction
opposite the direction of rotation of the armature when running as a generator,
from the slot into which the part of the main winding passes to which it is con-
nected. After traversing the length of the slot, it crosses at the far end to the
other side of the armature and returns through the diametrically opposite slot,
after which it is connected to the commutator section opposite it. Thus all the
visible junctions marked DD belong to the commutator coils that are connected to
the commutator sections on the side diametrically opposite to that part where the
covering is removed in the drawing, while the commutator coils, the ends of which
are seen in the drawing connected into their respective commutator sections, pass
around the armature and are joined to the main winding on the opposite side at
corresponding points diametrically opposite to the junctions lettered D D. The
several commutator coils B'B' 133 which are marked with a minus sign form the
commutator connections for the second or top half of the main winding, and those
marked with a plus sign form the commutator connections for the first or lower
half of the main winding. The points in the main winding from which the current
is drawn are approximately on the opposite side of the armature to that on which
are the commutator sections to which they are connected through the commutator
coils. The commutator coils and the main winding are wound in the same direction.
Thus assuming the armature winding to have been passed around the armature from
left to right on the top, and from right to left below, and the successive sections of
the winding to have been put on in such a manner that each succeeding one is a
step further in the direction in which the armature is represented as moving, then
in like manner the commutator coils will be wound from left to right over the top
of the armature and from right to left below. The commutator coil B'+ being
under the trailing tip or horn N* of the pole piece N, the machine being con-
sidered as a generator, has an E.M.F. generated in it equal to that generated in
one turn of the main winding, and the commutator section connected to it being
under the brushes, the main current is drawn through this coil. The path of the
current in the commutator coils, commutator sections, and brushes, is indicated by
arrows. The coil B+ has a large arrow drawn upon it to indicate that the main
portion of the armature current is passing to the commutator section E¹ and thence
to the brush F+ through this coil. In like manner the coil marked B'- also
has a large arrow drawn upon it to indicate that the main portion of the current
is passing through it back into the main winding. This arrow is shewn divided
into two towards the point, to indicate the division of the current into two parts at
the junction with the main winding. A small arrow is drawn upon each of the
commutator coils marked B'+ B²- B³+ B³-. The small arrows on B'+
and B³- are intended to indicate that the current in these coils is approaching

page_text: -
zero in consequence of the action before described, and that by the time the
corresponding commutator sections have broken connection with the tips of the
brushes, only one pair of which can be clearly seen in Fig. 2, the current in these
coils will be just at the zero point, and the break will thus be sparkless. The
small arrows on coils B+ B- are intended to indicate that a current is just
starting in these coils owing to the connection being established between the
brushes and the corresponding commutator sections. As the rotation proceeds,
the commutator coils marked B'+ B'- will move away from under the magnet
pole N, and the E.M.F. generated in them will rapidly fall, consequently the
current in B²+ and B' will diminish, and that in B+ and B will increase at
a corresponding rate until, when the coils B+ and B³- have reached the position
shewn as occupied by the coils B'+ B', they will be carrying nearly the whole
current, and the coils B'+ and B will then have arrived at the positions shewn
as occupied by the coils B*+ B²- and the current in them will be approaching
zero. It will be seen that each of these commutator coils which has passed from
under the pole piece, during the time in which the corresponding commutator
section is still under the brush, is connected in parallel with the adjacent com-
mutator coil which is still under the said pole, the connection between the two
being completed through one section of the main winding which is also well out
from under the pole piece. The excess E.M.F. in the commutator coil under the
pole, over that in the main winding coil and the commutator coil which have passed
out from under the said pole, will be sufficient to reverse. the current in the main
winding and reduce that in the last mentioned commutator coil to zero just as the
commutator section connected to this coil leaves the brush, and thus a sparkless
break will be secured. A sparkless break will be thus obtained both when the
brushes have a backward lead and the machine is running as a generator, and also
when the brushes have a forward lead and the machine is running as a motor.
The effect of giving the brushes a backward lead when running as a generator
is as hereinbefore stated with reference to Fig. 1, that the portion of the main
winding of the armature situate between the field magnet poles, assists the exciting
coils of the field magnet by increasing the magnetic flux, with the result that a
rise in the E.M.F. generated will take place with an increase in the load put
upon the machine-a result hitherto obtained by compound winding of the field
magnets. The result of giving the brushes a forward lead when running the
machine as a motor, is that the current in the before mentioned portion of the
main winding still aids in increasing the effective magnetic flux thereby producing
greater stability of the magnetic field, and also an increased torque with an
increased load.
The density of the magnetic flux under the tip or horn of the magnetic pole
marked N (Figs. 1 and 2) will be increased when the armature current is
increased, owing to the well known effect of the current in the armature winding.
The result will be to make the commutator coils more active. A greater E.M.F.
will consequently be generated in the one for the time being under the pole tip N*
and a greater excess of E.M.F. will consequently be produced over that generated
in the section of the main winding in which the current is required to be
reversed and in the commutator coil which has moved away from the pole, than
would be the case with less current. Thus as a greater E.M.F. is required to
reverse the greater current in the armature sections, the required conditions are
produced nearly or quite automatically, that is to say, little or no shifting of the
brushes with varying current will be required. This inore or less perfect automatic
action I have found to be most pronounced with dynamo machines having toothed
or slotted armatures and short air spaces, and this invention is of special value for
such machines, as by its use, these machines can be made to run sparklessly even
though the air space be made very short, and when this is done, shorter and con-
sequently lighter field magnets and less exciting force suffices, so much so that
by means of my invention I can when desirable entirely dispense with winding
upon the field magnets, in which cases I may make the field magnet poles to

page_text: embrace a considerably smaller portion of the armature than is usual. Fig. 3. is
a diagrammatic representation of field magnets and armature designed to work
without winding upon the field magnets. G is the armature core. H. H. are the
magnets. It will be seen that if the machine is constructed according to my
invention, as herein before described, to run with a backward lead when running as
a generator, or a forward lead when running as a motor, the commutator brushes
being set approximately on the line I. I a considerable portion of the armature
winding will tend directly to produce the required magnetic flux through the said
armature, and also through the field magnets.
The lengths of wire which are to form the commutator coils
may be connected
to the main armature winding as the winding operation proceeds. The ends of the
said lengths may be either coiled up to keep them out of the way until the main
winding is finished after which they can be wound into their respective positions
over the main winding; or the said lengths of wire may be wound as soon as
convenient into their proper places either above, below, or in between the main
winding wire or wires.
I have found it convenient to joint short lengths of insulated preferably flexible
conductor at convenient points between the sections of the main winding during
the winding operation and then to put on the commutator coils leaving the ends
free. The commutator coils can then be connected to the flexible ends after the
winding is completed. The amount of lead of the commutator coils as compared
with the main winding sections to which they are connected, can then be readily
altered if desired.
When the dynamo or motor is required to run in either direction at will, I may
employ two independent commutators and two sets of commutator coils and give
the set of commutator coils connected with one commutator a lead in one direction
with reference to the armature coils and those connected with the other com-
mutator an equal lead in the opposite direction. One commutator will then be used
when the machine is running in one direction, and the other when the machine is
running in the opposite direction, the brushes being lifted off the commutator
which is not in use.
Fig. 4 is a diagrammatic view illustrating this construction as applied to a
machine having a gramme armature and intended to run as a motor with forward
lead. A is the main armature winding. B B are the commutator coils of one
set; they are connected as before to the armature winding and to the respective
strips of the commutator Ex which will be in use when the machine is running in
the direction of the arrow shown in full lines. B* B* are the commutator coils
of the other set, connected to the armature winding and to the respective strips of
the commutator E which will be in use when the machine is running in the opposite
direction and which will be fixed on the armature shaft at the end of the armature
opposite to that at which the commutator Ex will be located. F³ is one of the
brushes for the commutator E, and F is one of the brushes for the commutator E³.
M M are the field magnet poles.
When the machine is to run in the direction of the full arrow, the brushes F*
and Fy must be moved into the positions shown in full lines so that the brushes F* and
commutator E will alone be operative.
When the machine is to run in the direction of the dotted arrow, the brushes Fz
and F must be moved into the positions shown in dotted lines so that the
brushes F and commutator E will then be alone in use.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed I declare that I do not
claim broadly connecting the sections of the armature winding to the commutator
strips through conductors arranged to pass through the magnetic field with the
object of overcoming wholly or partially the spark at the commutator, but what I
claim is :-
1. In a dynamo electric machine of the kind in which the commutator strips

page_text: are connected to the sections of the armature winding through commutator coils in
which an electro-motive force is set up when the machine is running, connecting
each of the said cominutator coils to the armature winding in such a manner that
it will have a backward lead with reference to the point between sections of the
armature winding to which it is connected, when the machine is running as a
generator, and a forward lead when the machine is running as a motor, and
arranging the commutator brushes so as to have a backward lead when the
machine is running as a generator and a forward lead when it is running as a
motor, the arrangement in each case being such that the armature current will tend
to increase the total magnetic flux, and that the resultant E. M.F: induced in any
two of the commutator coils and in the section of the armature winding that
connects them will reverse or tend to reverse the current in the said section of the
armature winding and reduce to zero the current in the commutator coil connected
to the commutator strip that is about to leave the commutator brush at the time
when one of the said two commutator coils is under one of the horns of the field
magnet poles that is strengthened by the armature current and the other has passed
from under the same and the two corresponding strips of the commutator are con-
nected by a commutator brush, substantially in the manner hereinbefore described
with reference to Figs. 1 and 2 of the drawings.
2. A dynamo electric machine of the kind herein before referred to with reference
to Fig. 3. of the drawings, in which the armature coils are connected to the com-
mutator segments through commutator coils and the brushes are arranged with
reference to the field magnet poles all in the manner referred to in the preceding
claim, so that the magnetic flux will be produced mainly or entirely by the current
in the portion of the armature winding which is for the time being between the
field magnet poles.
3. A dynamo electric machine constructed with two independent commutators
and with two sets of commutator coils arranged as set forth, the set of commutator
coils connected to one commutator having a lead in one direction relatively to the
armature coils, and the set connected with the other commutator having an equal
lead in the opposite direction, so that one or other of the commutators can be used
according to the direction in which it is desired the said machine shall run, the
brushes being lifted off the commutator that is not in use substantially as
described.
W. B. SAYERS.
W. Lloyd Wise,
46, Lincoln's Inn Fields, London, W.C., Agent for the Applicant.