Improvement in Laminated Armatures for Dynamo-electric Machines.
Year: 1899

page_text: Date of Application, 29th Sept., 1899-Accepted, 11th Nov., 1899
COMPLETE SPECIFICATION.
Improvement in Laminated Armatures for Dynamo-electric
Machines.
I, JAMES BURKE, of Oudenarderstrasse 23/30, Berlin, in the Empire of
Germany, 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:-
Armature cores as usually constructed have notches all round their peripheries,
which receive the armature winding.
One of the limits of capacity of an armature, whether of a generator or of a
motor depends chiefly on the development of sparks on the commutator.
One of the principal causes of such sparking is the condition of the armature
teeth as they pass between two magnetic poles. In this position, which may
be called the commutation zone, the teeth are magnetized only to a small degree
and the windings adjacent thereto have a large self induction at reversal, which
condition may be regarded as the chief cause for sparking.
If it were possible to give the armature teeth during their passage through the
commutation zone, a high magnetic saturation, the sparking limit might be con-
siderably extended, as the self induction is thereby reduced.
The present invention relates to means, whereby the armature teeth are made
to have a high degree of magnetic saturation during their passage through the
commutation zone, as I shall describe referring to the annexed drawings, Figs. 1,
2, 3 and 4, which represent armature discs S, having teeth z, in and near which
I punch slots which produce two effects:
First: Part of the magnetic flux is forced into the teeth that are adjacent to
the armature coils under commutation, and-
:
Secondly A more uniform distribution of magnetic flux is maintained in the
air gap by interposed magnetic reluctance in the armature core.
In Fig. 1 the slots s are radial extending from the middle of the teeth towards
the axis. In Fig. 2 instead of each radial slot being cut in an uninterrupted
line, it is made in two parts one part in the armature tooth and one in the inner
part of the core, the two slots being in one line; this change does not produce
any considerable change in the result caused by the arrangement shewn in Fig. 1,
but the effect being in both cases nearly the same.
In Fig. 3 the armature teeth are left without slots, only the inner core of
the armature being provided with slots, thereby producing a more uniform dis-
tribution of magnetic flux in the air gap, while an increased saturation in the
armature teeth would only be obtained to a very limited degree.
Fig. 4 shews another modification by which a considerable part of the magnetic
Hux may be directed through the armature teeth, thus increasing their magnetic
saturation while a modifying effect on the distribution of the magnetic flux in
the air gap would not be attained by this arrangement of the slots.
Instead of making the slots straight they may be curved or undulated, and
arranged in many different ways, their object being to exercise an influence in
directing part of the magnetic flux to those parts of the armature where an
increased magnetic action or saturation is desired.

page_text: This method of directing the magnetic flux within the armature is not limited
to toothed armatures, but it may be employed to advantage also for smooth
armature cores.
Having now particularly described and ascertained the nature of this inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is:
The construction of a laminated armature for a dynamo-electric machine in
which the laminations are provided with slots so arranged that part of the
magnetic flux is forced to follow a defined course for the purpose of increasing
the magnetic saturation in the armature teeth and also as a means for obtaining
a more uniform distribution of the magnetic flux in the air gap, substantially
as described.
Natal th: 0041.
19 ་
1
1000
ABEL & IMRAY,
Agents for the Applicant.