Improved Arrangement for Exeiting the Magnets of Dynamo Electric Machines.
Year: 1899

page_text: Date of Application, 2nd Feb., 1899-Accepted, 1st Apr., 1899
COMPLETE SPECIFICATION.
Improved Arrangement for Exeiting the Magnets of Dynamo Electric
Machines.
I, MAX DÉRI, of I Reichsrath Strasse, No. 3, Vienna, Austria, 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:-
My invention relates to arrangements for exciting the magnets of dynamo
electric machines such as were described in the Specification to Patent No. 15203
of 1898, in which a construction of the field magnets and connections of the
armature and field magnet windings were set forth whereby the prejudicial
reaction of the armature currents was prevented.
I have since found that with the arrangement described in the said specification
whereby a fixed resulting field was obtained, a certain disposition of winding of
the compensation coils is the most advantageous for enabling the machine to
work without sparking.
For this purpose it is necessary that the flow of magnetic force which is excited
by the compensation coils shall, both as regards its totality and as regards its
maximum value, be equal and contrary to the flow emitted by the armature.
As the field excited by the armature currents (armature field) always has a
distribution corresponding to the sinus law, on account of the uniform winding
of the armature surface, the most effective compensation will be obtained by also
winding uniformly with the compensation coils the entire periphery of the field
magnets which is presented to the armature.
With such an arrangement the magnetic flow transversely to the main field
will be entirely neutralised.
Figures 1, 2 and 3 of the drawings shew diagrams of the armature field
represented by the sinus curve a; the compensation opposite field is represented by
the curve and the field resulting from both of the curves is represented
by rand. The armature periphery corresponding to the length of a pole
distance is here shewn developed as a straight line.
m
a
a
If, as shewn at Figure 1, the total values of the magnetic flow, that is to
say, the areas o ao and o co were equal, but the maximum values m
and m
c were different, a resulting field in the form 1 would be produced.
If on the other hand, as at Figure 2, the maximum values
and m c were equal, while the areas are different, then the resulting field would
have the form 2. But if both the form and the strength of the magnetic
flow, that is to say, the area and the maximum value, are equal, as in Figure 3,
according to the present invention, then no transverse field will result.
Having now particularly described and ascertained the nature of this
invention and in what manner the same is to be performed, I declare that what
I claim is:-
In the arrangement for exciting the magnets of dynamo machines referred to
in the Specification to Patent No. 15203 of 1898: the method of forming the

page_text: compensation coils by providing the periphery of the field magnets presented to
the armature with compensation coils that are as uniformly arranged as the
armature windings, so that the magnetic flow produced by the compensation coils,.
which is directed contrary to the armature field, shall be practically equal to
the sinus shaped armature field, both as to form and strength substantially as
described.