Improvements in Armatures of Dynamo Electric Machines.
Year: 1891

page_text: Date of Application, 35th Nov., 1891-Accepted, 2nd Jan., 1892
COMPLETE SPECIFICATION.
Improvements in Armatures of Dynamo Electric Machines.
I, JOHN NEBEL, of 35 Maryon Road, Charlton, in the County of Kent,
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:-
In my Specification No. 4824 of 1890 1 described two modes of winding armatures
of dynamo electric machines with multiple conductors so as to avoid some of the
evils resulting from the use of comparatively few conducting bars each of large
section. Since filing the said Specification I have worked out certain general
principles according to which armatures can be made with multiple conductors
having their connections to each other and to the segments of the commutator so
arranged that even when large currents are generated there is little or no sparking
In order that the
at the commutator and very little heating of the armature.
principles of my invention may be more clearly understood, I shall take the case of
an armature having few couductors each of large sectional area as it would be
usually made and shall shew how these conductors may be subdivided and connected
so that, instead of only the ordinary two parallel paths for current from brush to
brush of the commutator, there may be any even number of such parallel paths,
each carrying a fraction of the current which is the less, the greater the subdivision
of the conductors.
Figure of the accompanying drawings shews diagrammatically an ordinary
arrangement of conductors in a drum armature.
Figure 2 shows how these conductors may be subdivided and connected according
to my invention.
Referring to Figure 1, A indicates the rectangular copper bars, the curved dotted
lines E indicate the connections at one end of the drum and the full curved lines D
indicate the connections at the other end of the drum and to the commutator
segments C. B B indicate the brushes. As there are from brush B to brush B'
two parallel paths, each bar A has to carry half the total current produced by the
machine.
The diagram shows only 12 bars, when the number of bars is increased, the
objections still exist though to a less degree.
Now, according to my invention, I divide each of the conducting bars into 2, 3
2 bars according as
or more, say n, sections and then add or subtract 2, 4 or 2 n
the conductors have been divided into 2, 3 or n parts and I make the end con-
nections and commutator segments proportional to the number of bars.
Each bar is then connected by the curved end connections, not to the bar exactly
opposite, but to the 2nd 3rd or th bar before the opposite one according as the
conductors have been divided into 2, 3 or n parts.
The bars are thus connected in series or in one continuous circuit over the
armature and as each brush is arranged to touch always 2, 3 or a commutator
segments according as the bars consist of 2, 3 or n parts, there are from brush to
brush 4, 6 or 2 n parallel paths for the current, and consequently each bar has to
carry only th, th or nth of the total current.
If, for instance, the original armature had 12 bars and it were desired to divide
each into two sections making 24 bars, to this Lumber there should be added 2 bars
making a total of 26 or from 24 should be subtracted 2 bars leaving a total of 22.
In like manner each of the 12 bars might be divided into 3 sections, and then to the
36 so obtained should be added 4 bars or from the 36 should be subtracted 4,
thus giving a total of 40 or of 32 bars.
Figure 2 shews diagrammatically such an arrangement for conductors divided

page_text: into three sections with 4 bars subtracted making a total of 32 bars and 16
commutator segments.
In this case, each bar has to be connected by the curved end connections to
the 3rd bar next before the bar directly opposite, following always the same
direction round the periphery. Thus the bar 1, to which 17 is directly opposite is
connected through the commutator segments to 14. Again 14 has its end connection
not to 30 directly opposite, but to 27, and so on.
The brushes on each side never
touch less than three segments. In this case from brush to brush there are
6 parallel paths, therefore each bar has to carry only th of the current.
It is an advantage of this arrangement, as compared with a system of independent
parallel circuits, that it is quite symmetrical whatever be the number of the parallel
circuits, requiring at both ends of the armature exactly similar end connections,
such as cannot always be used with independent parallel circuits.
This system of winding is applicable to multipolar machines as well as to bipolar
machines. If, for example there be 4, 6 or generally 2 m poles, it is only necessary
to multiply by 2, 3 or m the number of bars for a bipolar machine and to connect
each bar by the curved end connections, not to the bar th, th or mth of the
360°
,
2m
but to
way round, that is to say not to the bar at a distance of 90°, 60° or
the second, third or nth bar before that bar according as the division of the bars
has been into 2, 3 or n parts. Thus, referring to Fig. 3 which shews diagram-
matically the winding for a machine having 4 poles and having each of its
conducting bars divided into 3 parts, it will be seen that each of these part bars,
for instance A,is connected by the curved end connection D to the commutator
segment C and thence not to A' which is 90° from A, but to B which is a bar 3
before A. Again, following the dotted lines E the bar B is connected not to B¹
which is 90° from B but to F which is 3 before B. And in like manner all the 64
bars are connected round the whole circumference to each other through the 32
commutator segments. There are as many brushes as there are poles, that is to
say 4, each bearing always on 3 commutator segments, and each pair of opposite
brushes connected parallel. Instead of continuing the connections round all in one
direction as shewn in Fig. 3, they may be carried as shewn in Fig. 4 first, as before,
forward from A to B which is 3 before A', then backward from B not to B' which
is 90° from B, but to F which is the 3rd bar beyond B¹.
For applying this system of winding to ring armatures, each conductor of the
ordinary winding may be supposed to be divided into 2, 3 &c. parts and 1 part
may be added or subtracted in order to determine the new number of conductors,
each of which is to be connected to the 2nd, 3rd or th conductor following as
shewn in Fig. 5 representing diagrammatically the winding of a ring armature
having each of its 16 conductors divided into 3 parts and I added, making a total
of 49 with the same number of commutator segments. In this case, as n = 3, each
conductor connects to the 3rd in advance of it, for example A through the com-
mutator segment C to B which is the 3rd in advance from A. The number of
brushes should be the same as the number of poles in the field, each brush bearing
on n segments and the alternate brushes connected parallel.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. A drum armature for a bi-polar dynamo-electric machine having each of its
conducting bars divided into 2, 3 or n sections and this number increased or
diminished by 2, 4 or 2 π- 2, each bar of the number so determined being
connected, not to that opposite to it, but to the 2nd, 3rd or nth before the opposite
bar, through commutator segments of which there are half as many as there are
bars and on 2, 3 or n of which each brush is arranged to bear, substantially as and
for the purposes set forth.
2. A drum armature for a dynamo electric machine of 4, 6 or 2 m poles having

page_text: its conducting bars divided into 2, 3 orn sections as for a bipolar machine, the
number so produced being multiplied by half the number of poles, and each bar
being connectel, not to the bar which is th th or mth of the circumference
round, but to the 2nd, 3rd or nth bar before that through commutator segments of
which there are half as many as there are bars, and on 2, 3 or a of which each
brush is arranged to bear, there being as many brushes as there are poles, sub-
stantially as described.
3. A drum armature for a multipolar dynamo electric machine such as is referred
to in the preceding claim, but with each bar connected forwards not to the bar
which is th, th ormth of the circumference round but to the 2nd, 3rd or nth bar
before that, and backwards to the 2nd, 3rd or ath bar beyond that, the commutator
segments and brushes being arranged in the manner referred to in the preceding
claim, substantially as described.
4. A ring armature for a dynamo electric machine having each of its conductors
divided into 2, 3 or n parts and the number so produced increased or diminished
by 1, each of these conductors connected to the 2nd, 3rd or ath in advance through
a commutator segment of which there are as many as there are conductors, and
on 2, 3 or a of which each brush is arranged to bear, there being as many brushes
as there are poles, substantially as described.
Dated this 30th day of November 1891.
ABEL & IMKAY,
Agents for the Applicant.