Improvement in Alternating Current Motors.
Year: 1890

page_text: COMPLETE SPECIFICATION.
Improvement in Alternating Current Motors.
We, MICHAEL VON DOLIVO-DOBROWOLSKY, Electrician, and the Company
"ALLGEMEINE ELEKTRICITÄTS-GESELLSCHAFT," both of No. 22, Schiffbauer-
damm, Berlin, Prussia, 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 :—
Our invention relates to such electric motors as are driven by a plurality of
alternating currents of respectively differing phases.
As is well known, motion is produced in the said motors in this manner that the
alternating currents are caused to generate in a body of iron magnetic poles which
continuously alter their position, and that an armature placed movably under the
influence of the said poles, is forced by the latter to partake of their motion.
The improvement forming the subject of our invention consists in the particular
arrangement and combination, with the motor, of the conductors serving to receive
the operating currents, and its purpose is to simplify the motor, to impart to it
greater stability, to enhance the security of its keeping in working order, and to
increase its useful effect.
The conductors consist in a limited number of thick bars of a well-conductive
material, such as copper, the said number depending upon the number of alternating
currents employed. If, for instance, there is but one pair of circum-rotating poles,
and if two alternating currents are employed whose phases are shifted in respect to
each other by one quarter of a phase, the number of conductor-bars is four, while
if, with the two poles, three alternating currents having their phases shifted by one
sixth of a phase, are used, six bars are wanted, &c. These bars are passed through
the body of iron composed of divisional parts, such as disks, and they are insulated
therefrom. Besides, they are all well-conductively connected together at one end,
for instance by a disk, a ring, or a star of metal, while to the other ends are
attached the wires that supply the currents. This system of connecting together
at one point the conductors appertaining to different circuits, is possible because in all
the conductors there is, from the source of current to the aforesaid point of
connection, the same decrease of tension, so that the individual circuits would
present the same potentials at the said point even if they were not connected
together.
In the annexed drawing
Fig. 1 is a transverse sectional view of a motor carried out according to our
invention and having six conductor-bars.
Fig. 2 is a perspective view of the system of connected bars belonging thereto.
Figs. 3 and 4 are like views of a motor with four conductor-bars.
C
Fig. 5 is a longitudinal sectional view corresponding to both Figures) and 3.
In Figs. 1, 3 and 5, a is the body of iron composed of a number of annular
disks, bb, c c, d d', Figs. 1, 2, and 'b', e e¹ Figs. 3, 4, are the conductor-bars, the
opposite ones whereof are connected to the respective wires of the different circuits;
e are conductive rings to which the bars are fixed. The thick lines i denote the
insulating-films serving to prevent electric contact between the bars and their
connection e on one hand and the body a and other parts on the other hand. fis
the armature and g the shaft carrying the same, the said shaft being mounted in the
bearings h. The motor with six bars represented by Figs. 1 and 2 is designed for
three alternating currents whose phases are shifted by one sixth of a phase, while
the motor represented by Figs. 3 and 4 is adapted for two alternating currents
having their phases shifted by one quarter of a phase.

page_text: 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:
In an electric motor driven by alternating currents of respectively differing
phases, the combination, with an iron body a, of a number of conductor-bars, such
as bb, c c, &c., passing through the said body and insulated therefrom, means for
conductively connecting all the said bars together at one end, and a number of
current supply conductors connected to the other ends of the bars, substantially as
described.
Dated the 15th day of December 1890
J. H. JOHNSON & Co.,
Agents.