Improvements in Dynamo Electric Machines.
Year: 1898

page_text: Date of Application, 28th Oct., 1898
Complete Specification Left, 28th July, 1899-Accepted, 28th Oct., 1899
PROVISIONAL SPECIFICATION.
Improvements in Dynamo Electric Machines.
We, WILLIAM BROOKS SAYERS, of Glenwood, Bearsden, near Glasgow, in the
County of Dumbarton, Electrical Engineer, and HENRY ALEXANDER MAVOR, of
47, King Street, Mile End, Glasgow, and MAVOR & COULSON, LIMITED, also of
47, King Street aforesaid, Engineers and Electricians, do hereby declare the
nature of this invention to be as follows:-
This invention relates to dynamo electric machines in which the commutation of
the armature current is effected by means of commutator coils acted on by the main
pole or poles, or by a main pole and supplementary or reversing pole, or by
independent reversing poles, as variously described in the Specifications of former
Letters Patent No. 16572 of 1891, No. 10298 of 1893, and No. 27209 of 1896 and
in the Specification of an Application for Letters Patent No. 5177 of 1898, and it
has for object to increase the current output, as far as regards the sparking limit,
with a given size of armature, to increase the allowable error in setting the brushes
upon the commutator while still maintaining a fixed position for all loads, and to
render it practicable to commutate with a relatively weaker reversing field than
heretofore and thus reducing the value of the electromotive forces in action during
the process of commutation, whereby the tendency to spark with a given load is
correspondingly reduced. The invention also has for object to retain the com-
pounding effect due to armature reaction while using the reversible form of com-
mutator coils with the hereinafter described arrangements of the poles which act
upon them. The first mentioned object is attained according to this invention by
so arranging the armature windings that the period of time occupied by the
reversal of the current during commutation will be greater than is the case
with the arrangements heretofore described.
In the arrangements described in the Specifications of Letters Patent No. 10298 of
1893 and No. 27209 of 1896 and of Application No. 5177 of 1898, the span between
the poles or pole tips which act upon the commutator coils at the moment of
commutation is slightly greater than the distance apart of the two sides of a
commutator coil. With this arrangement the period of time occupied by the
reversing of the current in a section of the armature winding undergoing reversal
is equal to the time occupied by the armature in turning through an angle equal
to in the case of a single wound armature and where n is the number of sections
360 × 2
360
n
into which the armature winding is divided or to
n
cases of double or triple windings respectively, or generally to
is the number of windings upon the armature.
363 × 3
or
in the
n
380 × P
where P
n
According to the present invention instead of making the distance between
the poles which act upon the commutator coils at the time of commutation rather
greater than the distance between the two sides of a commutator coil, the distance

page_text: between the said poles is made rather greater than the distance between one
side of one commutator coil and the opposite side of the next adjacent commutator
coil, or next but one, or next but two, or even more, the result. being that with a
proper gradient in the reversing field, the periodicity of reversal will be reduced
to approximately one half if two commutator coils lie within the span between
the poles, or one-third if three commutator coils lie within the span, and so on.
It is to be understood that the brushes are to be adjusted, to make contact between
the commutator sectors for the required time, and that. varying the width of tread
of each brush will affect the period of reversal, so that any intermediate periodicity
between those indicated can be secured by suitably adjusting the tread of the
brushes.
→
The poles which act upon the commutator coils may be the tips of the main field
magnet poles in which the entire flux both. for producing the effective E.M.F. of
the machine and also the reversing flux is produced by the armature current, as
described and illustrated in the Specification of Letters Patent No. 16572 of 1891
or the imagnets may be wound with shunt coils, or shunt and series coils, in the
ordinary way, and used with or without any of the forms of reversing poles
described in the other specifications hereinbefore referred to.
⋅
When it is desired to make the machine excite its own field magnets by means of
the armature current, or to increase, by the same means, the total flux in the case
of a shunt machine, so as to obtain the effect of compound winding without series
coils, the disposition of the commutator coils with respect to the main winding
is made different from that described in the Specification of Letters Patent
No. 10298 of 1893; that is to say, instead of each commutator coil having its two
sides equally spaced from the point of connection beween two main coils, as
described and illustrated in the specification just referred to, the winding is so
arranged that one side-that is the leading side if the machine is to work as a
generator, shall be placed at a greater distance from the point of connection
between the main coils than, the other or trailing side. The result is that the
commutation is effected on the backward lead, and the resultant effect of the
armature reaction will increase the total flux and thus cause an increase in
the E.M.F. generated in the armature with increasing load. The compounding
effect, however, is only obtained when the machine is run in the direction for
which the winding has been, arranged.
Dated this 28th day of October 1898.
:
For the Applicants,
W. LLOYD WISE,
46, Lincoln's Inn Fields, London, W.C., Chartered Patent Agent.
COMPLETE SPECIFICATION.
Improvements in Dynamo Electric Machines.
We, WILLIAM BROOKS SAYERS, formerly of Glenwood, Bearsden, but now of
Albrecht, Milngavie, near Glasgow, in the County of Dumbarton, Electrical
Engineer, and HENRY ALEXANDER MAVOR, of 47, King Street, Mile End, Glasgow,
and MAYOR & COULSON, LIMITED, also of 47, King Street aforesaid, Engineers
and Electricians, 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 relates to dynamo electric machines in which the commutation
of the armature current is effected by means of commutator coils acted on by the
main pole or poles, or by a main pole and a supplementary or reversing pole, or
by independent reversing poles, as variously described in the Specifications of
former Letters Patent No. 16572 of 1891, No. 10298 of 1893, No. 27209 of 1896,
and No. 5177 of 1898, and it has for object to increase the current output, as far

page_text: as regards the sparking limit, with a given size of armature, to increase the allow-
able error in setting the brushes upon the commutator while still maintaining a
fixed position for all loads, and to render it practicable to commutate with a
relatively weaker reversing field than heretofore, thus reducing the value of the
electro-motive forces in action during the process of commutation whereby the
tendency to spark with a given load is correspondingly reduced. The invention
also has for object to retain the compounding effect due to armature reaction.while
using the reversible form of commutator coils with the hereinafter described
arrangements of the poles which act upon them.
The first mentioned object is attained according to this invention by so arrang-
ing the sections of the armature winding that the period of time occupied by the
reversal of the current during commutation shall be greater than is the case with
the arrangements heretofore described. In the arrangements described in the
Specifications of Letters Patent No. 10298 of 1893, No. 27209 of 1896, and
No. 5177 of 1898, the span between the poles or pole tips or reversing poles which
act upon the commutator coils at the moment of commutation is approximately
equal to or slightly greater than the distance apart of the two sides of a com-
mutator coil. With this arrangement the period of time occupied by the revers-
equal
ing of the current in a section of the armature winding undergong reversal
to the time occupied by the armature in turning through an angle equal to n
in the case of a single wound armature and where n is the number of sections
into which the armature winding is divided, or to.
360 × 2
n
or
360
360 × 3
in the
n
360 X P
where P
22
cases of double or triple windings respectively, or generally to
is the number of windings upon the armature.
According to the present invention instead of making the distance between the
edges of each pair of poles which act upon the commutator coils at the time of
commutation approximately equal to or slightly greater than the distance between
the two sides of a commutator coil, the distance between the said poles is made
rather greater than the distance between one side of one commutator coil and the.
opposite side of the next adjacent commutator coil or next but one, or next but
two commutator coil, or even more, the result being that with a proper gradient in
the reversing field, the periodicity of reversal, i.e. the number of reversals in a
given time, will be reduced to approximately one half if two commutator coils
lie within the span between the poles, or to one third if three commutator coils
lie within the span, and so on, the duration of each commutation being conse-
quently doubled, trebled and so on. It is to be understood that the brushes are
to be adjusted to make contact between the commutator sectors for the required
time, and that varying the width of tread of each brush will affect the period or
duration of reversal, so that any intermediate periodicity between those indicated
can be secured by suitably adjusting the tread of the brushes.
The poles which act upon the commutator coils may be the tips of the main field
magnet poles in which the entire flux both for producing the effective E.M.F. of
the machine and also the reversing flux is produced by the armature current, as
described and illustrated in the Specification of Letters l'atent No. 16572 of 1891,
or the magnets may be wound with shunt coils, or shunt and series coils, in the
ordinary way, and used with or without any of the forms of reversing poles
described in the other specifications hereinbefore referred to.
Fig. 1 of the accompanying illustrative drawings is a diagram showing an
armature winding corresponding to that shown in Fig. 3 of the said former
Specification No. 27209 of 1896 but with the adjacent pair of reversing pole
pieces P, spaced apart so as to have a span equal to or a little greater than that
occupied by two commutator coils B. that is to say to the span between one side B¹
of one coil B and the opposite side 132 of the next coil, the tread of each commutator
brush I being made equal in width to about two segments C of the commutator.
With this arrangement the period, i.e. duration of reversal will be twice as great

page_text: as would be the case if the said reversing poles were spaced apart so as to have a
span equal only to that of one commutator coil and the tread of each brush covered
only one segment of the commutator.
360 × 2
The bracket E indicates the distance through which a main coil or section of
the armature winding on the circumference of the armature will travel while
undergoing commutation, and the period of time occupied by the reversing of the
current will be equal to the period occupied by the armature in turning through
an angle equal to
whereas with the spacing of poles and relative span
of commutator coils shown in Fig. 3 of the former Specification No. 27209 of 1896,
the reversal would be accomplished during the time occupied by the armature in
turning through an angle of where n is the number of sections into which the
N
360°
12
armature winding is divided. The periodicity of commutation is therefore one
half and the duration of commutation twice as great in the improved arrangement,
and the reversal of a given current can be accomplished with a weaker field, or
with a more gradual gradient, so that a greater current can be reversed, and the
exact position and span of the commutator brushes require less accurate adjustment
for the attainment of a given result.
When the span or distance apart of the poles P P1 is equal to the span corre-
sponding to three commutator coils, the periodicity is reduced in the same way
to 3rd and so on.
The arrows a indicate the direction of the magnetic flux through the magnetic
circuit comprised between the connected pair of pole pieces P, P', their yoke
pieces y y and the armature core M as in the arrangement shown in Fig. 3ª of
Specification No. 27209 of 1896.
When it is desired to make the machine excite its own field magnets by
means of the armature current, or to increase, by the same means, the total flux
in the case of a shunt machine, so as to obtain the effect of compound winding
without series coils, the disposition of the commutator coils with respect to the
armature winding is made different from that described in the Specification of
Letters Patent No. 10298 of 1893, that is to say, instead of each commutator
coil B having its two sides B1, 132, equaily spaced from the point of connection A³
between two main coils, as described and illustrated in the specification just
referred to, the winding of the commutator coils is arranged as shown dia
grammatically in Fig. 2 so that one side-that is the leading side B2 of each
commutator coil B if the machine is to work as a generator in the direction of the
arrow, shall be placed at a great distance circumferentially from the point A2 of
connection between the armature coils than the other or trailing side B. The
result is that although both sides of each commutator coil are operative under
the adjacent pair of poles P, P¹ the commutation of the armature coils is effected
on the backward lead, and the resultant effect of the armature reaction will
increase the total flux and thus cause an increase in the E.M.F. generated in the
armature with increasing load, thus producing a compounding effect without the
use of compound winding upon the field magnet. The compounding effect, however,
is only obtained when the machine is run in the direction for which the winding
of the commutator coils has been arranged.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed we declare that what
we claim is :-
1. In a dynamo machine of the kind having commutator coils, arranging the
edges of each pair of poles which act upon the commutator coils at the time of
commutation, at a distance apart rather greater than the distance between one side
of one commutator coil and the opposite side of the next adjacent commutator coil
or next but one, two or more coils, substantially as described for the purpose
specified.

page_text: 2. In a dynamo machine of the kind having commutator coils, arranging each
of the commutator coils so that one of its sides shall be at a greater distance
circumferentially than the other side from the point between the armature coils
or sections to which the commutator coil is connected, substantially as herein
described with reference to the drawings for the purpose specified.
Dated this 28th dow of July 1800
For the Applicants,
W. LLOYD WISE,
46, Lincoln's Inn Fields, London, W.C., Chartered Patent Agent.