Electrical Transformers for Rotary-phase Currents.
Year: 1891

page_text: Date of Application, 22nd June, 1891
Complete Specification Left, 2nd Mar., 1892-Accepted, 2nd Apr., 1892
PROVISIONAL SPECIFICATION.
[Communicated from abroad by Messrs. SIEMENS & HALSKE, of Berlin, in the
German Empire, Electrical Engineers.]
Electrical Transformers for Rotary-phase Currents.
We, SIEMENS BROTHERS & Co. LIMITED of 12 Queen Anne's Gate,
Westminster in the County of Middlesex, Electrical Engineers, do hereby declare
the nature of this invention to be as follows:-
For the transformation of rotary-phase currents, ordinary transformers can only
be used in such manner that for each conductor carrying a single alternating
current a separate transformer is provided.
If an ordinary transformer were provided with as many primary coils as there
are separate alternating currents in the rotary-phase current, the iron core would
not become magnetised at all, because the rotary-phase current has the property
that the sum of all alternating currents contained therein is at every moment zero.
It is consequently necessary to distribute the primary and secondary coils in such a
manner in a rotary-phase current transformer that each coil is capable only of
magnetising a part of the iron core, the influence of the part magnetised at a certain
moment upon the parts carrying the other coils being no greater than that due to
the law governing the rotary-phase current system. Such a distribution is obtained
for example by arranging the coils upon an iron ring in the same manner as is done
in rotary phase electromotors. Such an arrangement is however subject to the
disadvantage that the magnetic lines of force have to pass through air spaces at
certain points.
On the other hand, the arrangements which overcome this difficulty have the
disadvantage that the separate radial limbs carrying the separate coils are closed
at their outer ends by longer iron connecting pieces than at their inner ends.
The present invention consists in effecting such a distribution of the iron and the
coils thereon that both the above-named defects are obviated.
For this purpose, the several limbs of the core, which as in ordinary transformers,
can be formed of a number of superposed thin plates, are all arranged parallel to
each other, so that their imaginary magnetic axes form the edges of a prism, and
the completion of the magnetic circuit at the two ends of the said prism is effected
by two precisely similar star, ring, or otherwise suitably shaped iron pieces.
It will be at once seen that by this means the greatest economy in iron is effected,
and at the same time a very advantageous construction obtained. Thus for example
three parallel prismatic or cylindrical iron cores with their primary and secondary
coils may be arranged in a triangular position and their ends be connected by
central star shaped pieces, or six or any other number may be arranged in a circle
and their ends connected by annular or disc shaped pieces.
Dated this 22nd day of Tuna 1001
ABEL & IMRAY,
Agents for the Applicants.
COMPLETE SPECIFICATION.
Electrical Transformers for Rotary-phase Currents.
We, SIEMENS BROTHERS & Co. LIMITED of 12 Queen Anne's Gate,
Westminster in the County of Middlesex, Electrical Engineers, 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:
For the transformation of rotary-phase currents, ordinary transformers can only
го

page_text: be used in such manner that for each conductor carrying a single alternating
current a separate transformer is provided.
If an ordinary transformer were provided with as many primary coils as there
are separate alternating currents in the rotary-phase current, the iron core would
not become magnetised at all, because the rotary-phase current has the property
that the sum of all alternating currents contained therein is at every moment zero.
It is consequently necessary to distribute the primary and secondary coils in such a
manner in a rotary-phase current transformer that each coil is capable only of
magnetising a part of the iron core, the influence of the part magnetised at a certain
moment upon the parts carrying the other coils being no greater than that due to
the law governing the rotary-phase current system. Such a distribution is obtained
for example by arranging the coils upon an iron ring in the same manner as is done
in rotary phase electromotors.
Such an arrangement is however subject to the disadvantage that the magnetic
lines of force have to pass through air spaces at certain points.
On the other hand, the arrangements which overcome this difficulty have the
disadvantage that the separate radial limbs carrying the separate coils are closed at
their outer ends by longer iron connecting pieces than at their inner ends.
The present invention consists in effecting such a distribution of the iron and the
coils thereon that both the above named defects are obviated.
For this purpose, the several limbs of the core, which as in ordinary transformers,
can be formed of a number of superposed thin plates, are all arranged parallel to
each other, so that their imaginary magnetic axes form the edges of a prism, and
the completion of the magnetic circuit at the two ends of the said prism is effected
by two precisely similar star, ring, or otherwise suitably shaped iron pieces.
It will be at once seen that by this means the greatest economy in iron is effected,
and at the same time a very advantageous construction obtained.
The accompanying drawing shews by way of example two arrangements for
carrying out the above described invention.
In the arrangement shewn in part sectional elevation and sectional plan at
Figs. 1 and 2, the transformer is constructed with three parallel cores S S S
forming the corners of a regular three sided prism the ends of which cores are
connected by star shaped iron picces V serving to close the magnetic circuit, each
of the cores having primary and secondary coils C C C, carrying the three
alternating currents composing the rotary-phase current.
Figs. 3 and 4 shew a vertical section and a sectional plau of a construction
adapted for a rotary-phase current with six alternating currents; in this case
there are six cores S with their coils C, the cores being connected at each end by
soft iron rings or discs V¹.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, we declare that what we
claim is:
Constructing transformers for rotary phase currents of a number of similar cores
such as S equal in number to the number of alternating currents constituting the
rotary phase current, each core serving to carry a primary and secondary coil, and
the cores being all so arranged in parallel positions as to constitute the corners of a
regular sided prism, while the magnetic closure of the cores at each end is effected
by two similar pieces of iron such as V, substantially as described.
Dated this 1st day of March 1892.
ABEL & IMRAY,
Agents for the Applicants.