Improvements in Electric Machines and Apparatuses for Differential- phase Alternating Currents.
Year: 1891

page_text: Date of Application, 10th Aug., 1891-Accepted, 31st Oct., 1891
COMPLETE SPECIFICATION.
Improvements in Electric Machines and Apparatuses for Differential-
phase Alternating Currents.
We, MICHAEL VON DOLIVO-DOBROWOLSKY, Electrician, and the Company
"ALLGEMEINE ELECTRICITÄTS-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, is designed to replace the system of connections of electric devices
(such as coils and lamps) for generating and receiving differential-phase alternating
currents described in the Specifications of the United States Patents No. 390414 to
Tesla and No. 390439 to Bradley, the said system consisting in this that the current-
generating and the current-receiving devices, which are equal in number, are
severally connected to form closed circuits, while the conducting or line-wires are
connected to equidistant points of the said circuits or (what amounts to the same
thing) to the united terminals of the respective devices. This system consequently
requires but as many line-wires as there are currents to be transmitted, and cach
of these wires forms a circuit with one of the other wires and one or more of the
generating devices on the one hand and receiving devices on the other hand.
The same may therefore be called the system of concatenated circuits. Or, if its
effect of producing in motors and transformers a rotating magnetic field, is taken
into account, it may also be termed the rotation current system.
If in this system the number of circuits conducting currents of consecutive
phases, is increased, the distance between the phases of the individual currents will
be diminished, and the prejudicial pulsations of the composite current, operating
for instance in lamps, as well as those of any magnetic field excited by the current,
will become smaller.
With two currents having their phases shifted by 90°, or one quarter of a phase,
the pulsations are still well observable; with three currents whose phases are
shifted by 600 or 120°, the oscillations of the magnetic field have only about
14 per cent. of the mean intensity; but if twelve currents are employed having
phasial differences of 30°, that is to say, if there are six consecutive impulsions, the
variations do not amount to more than about 4 per cent. The employment of very
many currents with such small phasial differences has, however, heretofore rendered
necessary a great number of line wires, which make the system very expensive.
If six currents pulsating successively, that is to say currents having 30° of phasial
difference, are led off independently of each other, twelve conducting-wires are
required; if, however, the circuits are connected together in the manner described
for three and four circuits by Bradley and Tesla in the aforesaid Specifications, one
half the number of wires is done away with, so that for six currents only six wires
are wanted, and for eight currents of 45° phasial difference eight wires.
Now, the object of our invention is to reduce the number of line-wires still
further, namely to one half as compared with the foregoing, so that with but four
wires eight currents of a phasial difference of 45°, and with but three wires six
currents of a phasial difference of 30° may be transmitted. For this purpose we
combine with a number of generating or receiving devices placed in closed circuit,
other like devices inserted between the points of connection of the former and the
line wires. In a dynamo, a motor, or a transformer these devices will consist in
coils placed on the respective cores in suitable position relatively to the other coils,
while for lighting purposes the said devices consist in lamps alike to those contained

page_text: in the closed circuit. This system we shall call the system of doubly concatenated
circuits. The advantages of the same are, that, with a given number of line-wires,
it allows of obtaining in generators a more quiet and unvarying production
and delivery of energy, of producing in motors and transformers circum rotating
magnetic fields being as far as possible free from pulsations and consequently of
higher efficiency, and of attaining in lamps and other electric apparatus a steadier
light or other effect.
In the annexed drawings
Figs. 1 to 4 are diagrams serving to explain the theory of the invention and the
combination of the parts in general.
Fig. 5 is a view of an annular core of iron (which may be the armature of a
dynamo or the field magnet of a motor) having four coils placed in concatenated
circuits with four line-wires according to the system of Bradley and Tesla.
Figs. 6 and 7 show two different arrangements of our new system of double
concatenation applied to a closed circuit comprising four coils.
Fig. 8 represents an annular core with eight coils connected to the line wires in
like manner as in Fig. 2.
Figs. 9 and 10 are views of a cylindrical armature of a motor provided with coils
respectively according to the old and the new system.
Fig. 11 represents an annular core with three sets of two coils each, in
concatenated connection with the line wires.
Fig. 12 shows the new arrangement with three like sets of coils.
In Fig. 13 there are two separate sets of three coils each, connected to three
line-wires, while in Fig. 14 these sets of coils are connected to three sets of two
.coils each of the new system.
Fig. 15 represents a combination of three sets of four coils each, in connection
with three line-wires, and Fig. 16 the new arrangement to be substituted therefor.
Fig. 17 is a view of a transformer with four coils placed in circuit and four other
coils for the primary currents, and eight coils for the secondary currents.
Fig. 18 shows a plurality of separate transformers connected together according
to our new system.
In Figs. 5 to 8 and 11 to 16 the pieces shown in dotted lines inside of the rings
denote armatures such as would be applicable in case the rings and coils were to
serve as field-magnets of motors.
20
The new system of connections rests on the following principle. If two
alternating currents of an equal number of alternations and equal mean strength,
but of different phases, are added together, a current will result having phases
intermediate to the former and whose strength, I, is computed by the formula:
1 = 2 i cos.
in which denotes the strength of the separate original currents and
>>
the angle of phasial difference. The result of such addition is shown graphically
by Fig. 1 in which the wave-lines represent the phases of the two original
currents, and the dotted wave-line 1' the phases of the resulting current.
In view of utilising this resulting current together with the original currents, the
current conductors are arranged in general as shown by the diagrams Figs. 2 to 4.
According to Fig. 2 three like coils ac (indicated by zig-zag lines) are connected
together to form a closed circuit; A B C are the line-wires, and A B C the new
or additional coils interposed between the latter and the points of connection of the
coils ac with each other. These coils may be the generating-coils of a dynamo
or the magnetising coils of a motor or the coils of a transformer, whether primary
or secondary.
Fig. 3 shows two closed circuits formed by the respective coils a b c and a¹ b c¹,
in combination with six additional or new coils A'B'C', A³ B² C, the coils A¹
and A being connected to the line-wire A, the coils B B to the wire B, and the
coils CC to the wire C.
Fig. 4 represents a system like to that illustrated in Fig. 2 except that the closed
circuit is formed by four coils a b c d, and that there are four new coils A' B' C'D'.

page_text: ·gs. 4, ɔ and 4 the zig-zag mes may, however, also represent lamps or sets
of lamps.
We shall now proceed to describe how the coils A'B'C', &c., are to be arranged-
together with the coils a b c, &c., on the core of an armature or of a field-magnet
under different conditions.
90
-
Taking in view Fig. 5, it will be perceived that the core-ring R is wound with
four coils a b c d placed at right angles to each other (alike to the same coils in
Fig. 4) and connected at their points of junction to the line-wires A B C D
according to the known system herein before referred to. Supposing the ring R
to be the armature of a dynamo, it is evident that the phases of the currents
induced in the said coils, are shifted one relatively to the other by 90°. Provided
these currents are of equal strength, which will ordinarily be the case, the current
in wire A, resulting as the sum of the currents in coils a and b, will have the
mean strength I = 2 i cos. = 1.4. The maxima of strength of the current in
wire A are, however, intermediate to the maxima of the currents in coils a and b.
Between each of the currents in wires A B C D and the respective composing
currents in coils a b c d there is therefore a phasial difference of 45°. Now, if
a portion of each of the wires A B C D conducting the currents I, is also wound
on the armature-ring R so as to form the coils A¹ B¹ C₁ D', as shown in two
different arrangements in Figs. 6 and 7, eight coils with currents of phasial
differences of 45° are obtained. If the number of convolutions of the coils A'B'
CD is made smaller relatively to that of the coils a bed in the proportion of
1 to 14, while the wires of the said coils A'B' C₁ D' are of correspondingly
larger sectional area, the product of the number of ampères multiplied by the
number of convolutions will be in all eight coils about the same, and the effect of
the wire-wound ring will be like to that of a ring of Bradley and Tesla having
eight coils, as represented by Fig. 8, though there are but four line-wires con-
nected to the former against eight to the latter.
Fig. 9 shows a cylindrical core R¹, having three coils a be arranged at angles
of 60° to each other, and connected in concatenated circuits to the three line-
wires A B C. Supposing this core to be the core of a motor-armature, the
currents to be employed for driving the same and flowing through the said line-
wires have a phasial difference of 60°. The current in wire A on passing over
into the coils a and b will split into two currents, the phases whereof differ by 30°
from the former. In like manner the currents in wires B and C split on passing
over into the respective coils bc and c a. Therefore, if a portion of each of the
wires A B C is coiled around the cylinder R' between the coils a bc, as shown in
Fig. 10, the new coils being marked A2, B2, C2, an armature will be obtained in
which the phasial difference of the currents is but half as large as in the armature
Fig. 9.
Fig. 11 represents an annular core with six coils connected in the old manner
for three currents of three different phases, while with the new system shown by
Fig. 12, twelve coils are obtained from which six currents of six different phases
are led off in the three line-wires.
The same difference of results is obtained by the new arrangement represented
by Fig. 14, as compared with the old one shown by Fig. 13. In both there are
two closed circuits with the respective coils a bc, a b¹ c' instead of the single
circuit in the preceding figures, but these circuits are substantially connected
parallel and may therefore be considered as one. By the combination of the coils
as in Fig. 13, however, only three currents with phasial differences of one third
of a phase are obtained, while by the combination of the pairs of coils A¹ B¹ C'
with the coils a'b c, a b¹ c', a doubling of the number of consecutive impulsions
(or bisection of phasial difference) is brought about.
In a similar manner as described with reference to Figs. 11 and 12 repre-
senting armatures or field-magnets of bipolar machines in which the opposite

page_text: coils a a, b, c c are connected to form virtually one coil, all those coils of
multipolar machines whose position relatively to the poles is the same, and which
convey currents of the same phase, may be united to form one set of coils. By
these means the new system of connections may be applied in like manner to
multipolar machines as to the bipolar ones. One half of the sets of coils
(instead of single coils) is in this case again connected to form'a closed circuit and
from this circuit the other sets of coils (instead of single coils) are branched off
at different points. Thus Fig. 15 shows a coil-carrying ring adapted to be used
as field-magnet in a four pole motor or an armature of a four pole generator, the
coils being arranged in the ordinary concatenated connection for currents of
phasial differences of 60°, while Fig. 16 represents the same ring with application
of the new system of double concatenation for a phasial difference of 30°
As has already been stated, the doubly concatenated circuits for producing a
rotation current, and obtained by the new system of connections, is to be applied
in current-generators if the highest performance and efficiency, and a steady
delivery of current, free from vibrations, is desired. The system is likewise
particularly useful for electric motors belonging to the multi-pliasial, or rotation-
current class, and in these motors the field-coils or the armature-coils or both may
be connected in the manner described. Moreover, the system may often be applied
with advantage in current-transformers constructed for currents of different phases,
and the double concatenation may be made use of for the primary coils or for
the secondary coils or for both. Fig. 17 represents a transformer for converting
four currents of 90° phasial difference into eight independent currents of 45°
difference, or vice-versa.
By Fig. 18 it is designed to show that a number of separate current-transformers
of common construction may also be connected according to the double concatena-
tion system. There is here represented the special case in which twelve currents,
1 to 12, differing from each other by one twelfth of a phase, are to be obtained
from three currents, flowing through the wires A B C, and having a difference
of one third of a phase. The circuits for the former are simply-concatenated in
the manner also shown by Fig. 8, while the circuits for the latter, i.e. the inducing
currents, are doubly concatenated, as in Fig. 12, in view of reducing the phasial
difference.
It is evident that the currents obtained by the transformer in double number
and of a phasial difference of one half, may again be doubled in another trans-
former, or sets of transformers. It is therefore easy to produce a large number
of currents of minimal phasial difference, by repeated double concatenation of the
circuits for a small number of currents differing in their phases, for instance, one
third of a phase.
By means of the new system of double concatenation applied to transformers, it
is moreover possible to produce currents differing in their phases by 90°, from
currents of 60° or 120° phasial difference, whereby it is rendered feasible to drive
two-phasial current motors with three-phase currents. To this end the currents
of 60° or 120° difference are first converted into currents differing by 30°, such as
the currents flowing in the circuits 1 to 12, Fig. 18, and from these the currents
of 90° phasial difference are selected and brought into cooperation. In Fig. 18
for instance the combination of the circuits 1, 2 and 4, 5, and that of the circuits 7,8
and 10, 11 would answer this purpose.
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 electric machines and apparatus which produce, or are operated by,
differential-phase alternating currents, the combination of three or more current-
producing or current-receiving devices, or sets of devices (such as induction-coils
and lamps) connected together to form a closed circuit or circuits, other electric

page_text: devices or sets of devices of the same kind, being alike in number to that of the
former, and severally connected with one terminal to equidistant points of the said
closed circuit or circuits and with the other terminals to the respective line-wires,
substantially as described.
Dated the 10th day of August 1891
J. H. JOHNSON & Co.,
47, Lincoln's Inn Fields, London, W.C., Agents.