Improvements in the Connections of Alternating Current Generators and Electric Motors.
Year: 1889

page_text: Date of Application, 5th Dec., 1889
Complete Specification Left, 27th Aug., 1890-Accepted, 18th Oct., 1890
PROVISIONAL SPECIFICATION.
Improvements in the Connections of Alternating Current Generators
and Electric Motors.
د,
We, MICHAEL VON DOLIVO-DOBROWOLSKY, Engineer, and the Company "ALLGE-
MEINE ELEKTRICITÄTS-GESELLSCHAFT,' a Joint Stock Company entered according
to the German Laws in the Register of Trades both of No. 26 Schlegelstrasse
Berlin, Prussia, do hereby declare the nature of this invention, whereof the said
Von Dolivo-Dobrowolsky is the inventor, to be as follows:-
Our invention relates to the method of imparting motion to the armature of an
electric-motor by causing the magnetic axis of the field-magnet thereof to be pro-
gressively shifted, or to rotate, through the medium of two or more alternating
currents whose phases of vibration follow each other in succession.
Among the means for producing such currents, one which may be considered the
most advantageous heretofore proposed, substantially consists in providing the
armature of the electric generator and the field-magnet of the motor each with
several coils placed on different diameters of the machines, or at an angle to each
other, and connecting the coils of the generator with those of the motor in such
manner that a number of circuits being independent of each other are formed. By
this method, certainly, alternating currents are obtained the phases whereof follow
each other; but the said method has various inconveniences.
According to our invention, the different coils, instead of being independent, are
conductively connected together in each machine, and the connections between the
respective coils of the two machines are such that the coils of the generator supply
electric impulsions to two or more of the connecting wires or mains simultaneously,
though these impulsions vary in degree relatively to each of them, and that each
impulsion transmitted through a main is distributed upon two or more coils of the
motor. All the circuits are therefore dependent upon each other.
The new system of connections which we employ for this purpose may be carried
out in two different arrangements shown by Figures 1 and 2 of the annexed drawings.
In both figures E is the rotating armature of an electric generator or dynamo,
a b c are three coils placed thereon, F is the field-magnet of the motor and a¹¹ c¹ are
the magnetizing-coils thereof.
According to Fig. 1 the coils a b c are all connected together so as to form a
continuous convolution. In like manner the coils a¹ 61 c¹ are connected together,
and the pairs of coils a b, bc, c a, are connected to the respective pairs, a' b¹, b¹c¹, c¹ a¹
by the mains def. In this case the coils are in parallel connection. The connections
between the said mains and the coils a be may be produced by the rings d² e² f², rotating
with the armature, the rods d'e¹ f' and brushes d³ ³ ƒ³.
In the arrangement shown by Fig. 2 the coils a b c do not form a continuous
convolution, and they are connected at one end only to the respective rings d² e² f2,
while at the other end they are connected together by the conductors ghi. In like
manner the coils a¹ care conductively connected at one end to the respective
mains d, e, f, while at the other. end they are connected together by the con-
ductors gh. Under these conditions the coils are all connected in series.
A modification of the said arrangements is obtained by connecting the coils
of the armature E parallel and those of the field-magnet F in series, or vice-versa.
Instead of but three coils any larger number may be employed.
Another modification in the construction of the generator consists in increasing the
number of poles of the field-magnet and providing the armature with as many groups
of coils as there are pairs of poles, the corresponding coils of each group, i.e. the coils
in which at any given moment like currents are induced, being connected to form a

page_text: set, and the different sets being connected in pairs to the mains in like manner as
described relatively to the single coils of the two-pole motor.
Dated the 5th day of December 188a
J. H. JOHNSON & Co.,
Agents.
COMPLETE SPECIFICATION.
Improvements in the Connections of Alternating Current Generators
and Electric Motors.
We, MICHAEL VON DOLIVO-DOBROWOLSKY, Engineer, and the Company "ALLGE-
MEINE ELEKTRICITÄTS-GESELLSCHAFT," both of No. 26 Schlegelstrasse, Berlin,
Prussia, do hereby declare the nature of this invention, whereof the said Von Dolivo-
Dobrowolsky is the inventor, and in what manner the same is to be performed, to he
particularly described and ascertained in and by the following statement :-
Our invention relates to the method of imparting motion to the armature of an
electric motor by causing the magnetic axis of the field-magnet thereof to be pro-
gressively shifted, or to rotate, through the medium of two or more alternating
currents whose phases of vibration follow each other in succession.
Among the means for producing such currents, one which may be considered the
most advantageous heretofore proposed, is described by Tesla in the Specification of
the United States Patent No. 381,968. The same substantially consists in providing
the armature of the electric generator and the field-magnet of the motor each with
several coils placed on different diameters of the machines or at an angle to each other
and connecting the coils of the generator with those of the motor in such manner that
a number of circuits being independent of each other are formed. By this method,
certainly, alternating currents are obtained the phases whereof follow each other; but
the said method has various inconveniences. Thus, if machines are employed having
two coils placed at a right angle to each other, and which therefore produce but two
currents, differing in their phases by one quarter of a phase, the sum of the
magnetizing forces of the two systems is not the same at every moment, and, in
consequence of these variations in the sum of forces, prejudicial magnetic pulsations
arise in the motor. These pulsations are limited or avoided, and the useful effect of
the motor is increased if three or more coils are employed, because in such case the
fluctuations in the magnetizing forces are less. Each of the independent circuits to
be established between the two machines, however, requires two conducting-wires, or
mains, or, if the return-conductors of all the circuits are united into one, there must
be one conducting-wire or main more than there are independent coils. Therefore, if
the number of the coils is increased to such extent that the said fluctuations in the
magnetizing forces are practically avoided, the great number of mains renders the
system very expensive.
According to our invention, the different coils, instead of being independent, as in
former arrangements, are conductively connected together in each machine, and the
connections between the respective coils of the two machines are such that the coils
of the generator supply electric impulsions to two or more of the mains simultaneously,
though these impulsions vary in degree relatively to each of them in the mains, and
that each impulsion transmitted through a main is distributed upon two or more coils
of the motor. All the circuits are therefore dependent upon each other. With this
mode of connection the total energy of all the currents acting on the motor is
practically the same at every moment, a far greater degree of uniformity in their
operation is consequently attained, and but as many mains are required as there are
coils in either machine. The said coils may be connected together in two different
manners adapted to be called parallel connection and connection in series.
The annexed drawings represent a generator A and a motor B, arranged and
combined according to our invention. Figs. 1 to 4 show the coils of each machine
in parallel connection, the different figures serving to illustrate the state and direction
of the currents produced by the rotation of the armature E. Figs. 5 and 6 show the

page_text: same machines with their coils connected in series. Fig. 7 represents the coils of
the generator connected parallel and those of the motor in series, while according to
Fig. 8 this arrangement is inverted. In Figs. 5 to 8 the armature G has been omitted.
Fig. 9 is a view of generator having four poles and two groups of coils.
In Fig. 1, D is the field-magnet and E the armature of the generator, while F is the
field-magnet and G the armature of the motor. N and S are the poles of the
magnet D. The armature E has three coils a, b, c, and the field-magnet F three
coils a, b, c, the coils of each machine being shown separated from each other a
short distance in order to render them more distinct; but they are so connected
together as to form a continuous convolution. d² is a contact-ring rotating with the
armature E, da rod connecting the ring d² with the wire which leads from the
coil c to the coil b, while d³ is a brush being in contact with the ring and to
which is connected the conducting-wire or main d. By means of like contact-
rings e² 2, rods elf and brushes e³ ³ sliding connections are established between
the pairs of coils a e, ba and the respective mains e f. The mains d e f are fixed
at de to the respective pairs of coils b¹ cl, a' c¹, a' b¹ of the motor B.
If the armature E, during its rotation in the direction of arrow 1, has attained the
position shown by Fig. 1, the coils a and c are exposed in equal degree to the influence
of the magnetic field; but one coil is above, the other below the neutral line kl. Two
equal currents 2, 3 of opposite direction are therefore at this moment induced in the
said coils a c. The currents simultaneously induced in the coil 6, neutralize each
other on account of the coil being by one half above and by one half below the line kl.
The said currents 2, 3 unite and pass through rod e', ring e, brush e³, main e (see
arrow 4) to point e, where the combined current divides again to flow in two branches,
according to arrows 5, 6, through the coils a¹ c¹ of the field-magnet F, through the
respective mains df (see arrows 7, 8), brushes d³ ³, rings 2 72 and bars d¹¹ to
the coils from which they issued. The coil b' at the time receives no current. The
currents 5 and 6 will under these conditions excite the field-magnet F in such manner
that the magnetic axis has the position N' S¹.
When the armature E has come into the position shown by Fig. 2, which is
60 degrees forward of the former position there will be induced in the coils b and c,
being now situated symmetrically to the magnetic field and to the neutral line,
contrary currents of equal strength, indicated by the arrows 9, 10, while the coil a is
without current on account of its receiving two equal but contrarily-directed inductive
impulsions. The course of the currents will under these conditions be as shown by
arrows in the said figure. The current in wire f has a direction contrary to that
which it had in the first instance; it must therefore, in the meantime, have once been
zero, and this is the case when the coil c is centrally opposite to the north pole N, so
that it is at the maximum point of induction. The magnetic axis of the electro-
magnet of the motor will now have the position N2, S2, Fig. 2, the same having
successively passed through all the positions lying between the one indicated by
line N¹ S', Fig. 1, and the said position N² S³.
After the armature E has rotated farther by another angle of 60 degrees, as
represented in Fig. 3, the currents that are induced, will flow as shown by arrows in
this figure, and the magnetic axis will have the position N³ S³.
Similarly it results that after the armature E has completed half a revolution, the
state of the currents will be as indicated in Fig. 4, the magnetic axis being then
at N* S. In like manner the following positions of the said axis may be
determined.
The final result of these considerations is that, by means of the described con-
nections, the rotation of the armature E produces a continuous progressive shifting of
the magnetic axis of the field-magnet F, and consequently a rotation of the armature G.
Besides it will be perceived that there is a gradual transition from the maximum
induction of one coil to that of the other, the total electric work or energy produced
being in consequence not subject to fluctuations.
Figs. 5 and 6 show the respective coils of the armature E and of the field-magnet F
connected in series, that is to say: the coil a is connected at one end, for instance at

page_text: the end which is forward during the rotation of the armature, to the like end of the
coil b by a wire g, the coil b is connected in the same manner by the wire / to the
coil c, and the latter by wire i to the coil a. Similar connections are established by
the wires g¹¹ between the coils a¹ be¹. The ends of the coils a a' not being thus
connected, are put in conductive communication with each other by the parts d¹ d² d³d,
the like ends of the coils by the parts e¹ e² e³ e, and those of the coils ce¹ by the
parts f1f2f3f.
If the rotating armature Ę is in the position Fig. 5, a current will be induced in
each of the two coils a c in the same manner as explained above with reference to
Fig. 1. The current from coil a passes through the wire i to coil c and, after uniting
its electro-motive force with that of the current in the latter coil, flows through the
connections f f f f to coil c and thence through wire to coil a', and returns by
the connections d d³ d² d' to coil a. The magnetic field produced by means of the
currents circulating in the coils a¹ and c¹, has its axis at N¹ S₁.
After one sixth of a rotation of the armature, the state of the currents and the
position of the magnetic axis will be as shown by Fig. 6, the axis having shifted by
the same angle as the armature E. Thus with the coils connected in series an
analogous effect is produced as with the parallel connection.
The respective coils of the armature E and of the field-magnet F may also be con-
nected together differently, that is to say the ones parallel and the others in series.
Thus Fig. 7 shows an armature E with parallel connections of coils and a field-
magnet F with coils connected in series, while Fig. 8 represents the contrary
arrangement. With regard to Fig. 7 it may be observed that, when the armature E
is in the position shown, and a current flows from the same through wire e to coil cl
this current passes from the latter partly through wire h¹, coil and back through
wire d, while the other part of the current takes its course through wire i¹, coil a¹ and
wire ƒ, the magnetic axis having then the position N' S', Fig. 7. If the coils are con-
nected as represented by Fig. 8, and if the armature E is in the position shown in this
figure, the current passing outward through wire f, will circulate partly through the
coil & and partly through the coils a' c', and return through wire d.
For all ordinary purposes three coils in the generator and three in the motor will
be found sufficient; but any larger number may be employed.
1
A modification in the construction of the generator consists in increasing the'
number of poles of the field-magnet and providing the armature with as many groups
of coils as there are pairs of poles, the corresponding coils of each group, i.e. the coils
in which at any given moment like currents are induced, being connected to form a
set, and the different sets being connected in pairs to the mains in like manner as
described relatively to the single coils of the two-pole generator.
Thus in the generator shown by Fig. 9, the field-magnet has four poles N S¹ N* S*,
while the armature carries two groups of coils, one group comprising the coils a b c,
the other the coils a* bx cx. The coils a and a* are connected together by the
wire a², the coils and 6x by the wire 62, and the coils c and cx by the wire c². The
connection of the two sets of coils a a*, cex with the contact-ring e2 is obtained by
the wires e e, that of the sets a ax, bbx with the ring f2 by the wires f¹f and that
of the sets bb, c cx with the ring d by the wires d¹ d.
The described connections of the coils with each other and with the mains may be
employed with advantage not only for operating alternating current motors, but also
in other cases, for instance, if the currents produced by an alternating-current
generator are to be converted by means of a transformer into currents of different
tension. The arrangement serving for this purpose is described in another Specifi-
cation of ours entitled "Improvements in Electrical Induction Apparatuses, or
Transformers," dated 5th December 1889 No. 19555.
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:
1. In electric generators the combination of three or more coils or sets of coils.

page_text: connected together either parallel or in series, and an equal number of mains connected
to the said coils or sets of coils, each main forming with each of the other mains and
one or more coils or sets of coils a circuit, substantially as described.
2. The combination of the armature of an electric generator and the field-magnet
of an electric motor, each comprising three or more coils or sets of coils connected
together either parallel or in series, and a like number of mains connecting together
the respective coils or sets of coils of the generator and of the motor, each of the said
mains forming with each of the other mains and one or more coils of the generator
and of the motor a circuit, substantially as specified.
Dated the 97th day of August 1900
J. H. JOHNSON & Co.,
Agents.