Improvement in Systems of Electrical Distribution.
Year: 1898

page_text: Date of Application, 2nd Aug., 1898-Accepted, 10th Sept., 1898
COMPLETE SPECIFICATION.
Improvement in Systems of Electrical Distribution.
We, THE BRITISH THOMSON-HOUSTON COMPANY LIMITED, of 83, Cannon Street,
in the City of London, Electrical Engineers, do hereby declare the nature of this
invention (which has been communicated to us from abroad by Charles P. Steinmetz,
residing at Schenectady, in the County of Schenectady, State of New York, United
States of America, Electrical Engineer, and in what manner the same is to be
performed to be particularly described and ascertained in and by the following
statement:-
The present invention relates to a system of electrical distribution, and comprises
certain improvements by which it is possible to obtain polyphase currents for
operating polyphase motors or other translating devices by interlinking a number
of sources of alternating electro-motive forces in such a manner that a desired
difference of pbase is maintained between the different machines, which difference of
phase is stable.
When a number of alternating electromotive forces are maintained in a closed circuit
by independently driven generating machines, the sum of all the electro-motive
forces must be zero and, representing the forces geometrically, all the electromotive
forces must combine to form a closed polygon. The fundamental feature of the
present invention consists in interlinking a number of alternating electro-motive
forces derived from independently driven machines in such manner that the polygon
thereby established, as above explained, must remain stable, the electromotive
forces being able to arrange themselves in a definite position. For example if
three ordinary independently driven alternating current machines are connected in
series and the three alternating forces assumed to be equal, then these alternating
forces will be represented geometrically by three lines of equal length, and such
lines can combine to form only an equilateral triangle. Thus when three machines
are coupled in this manner the resultant electromotive forces will be displaced in
phase by 120° which permits of a derivation of true three phase currents from the
three leads connecting the brushes of the different machines. In this instanco the
polygon is determined by having given the three sides necessary to fix the triangle,
which represents the combined electro-motive forces. If the voltage of the different
machines is equal the triangle formed, as already stated, will be equilateral, and
three phase currents may be obtained from the machines. If the quarter phase
currents are desired the voltage of the machines will be so proportioned that one is
substantially 1.40 times that of the other two, the other two being equal to ono
another. If currents 60° apart are desired these can be secured by making the
voltage of one machine substantially 1-73 times that of each of the other two.
When dealing with two electromotive forces the relation in which they will
combine is fixed by having given two sides and the intermediate angle of the
resulting triangle. Hence if two sources of alternating electro-motive forces are
used, and an induction motor in the manner hereinafter described, preserving the
angle between the electro-motive forces, substantially the same results may be secured
in this modified manner. If the two sources are independently driven and connected
in series directly, without the interposition of a phase controlling device, such as

page_text: the generator or the induction motor aforesaid the said forces would neutralizo
one anothers action that is, they would come to stable equilibrium when 180° apart.
When more than three electromotivo forces are combined, as for example, four,
it is impossible to fix the polygon which they will constitute by having given simply
the sides of the polygon, for it will be readily understood that four lines may
combine to form an indefinite number of polygons and so too of other polygons
except triangles. If four machines are used it becomes necessary therefore to fix
the polygon which they will constitute by the presence of other factors. This may
by done by using another machine fixing the diagonal of the polygon, or it may be
accomplished by an induction motor which determines the angle between the
diagonals. These different methods of practising the invention will be more
specifically set forth hereinafter, but it will appear from the foregoing that the
invention consists in combining the electromotive forces in, such manner that a
definite polygon of forces is formed whereby currents may be derived for operating
translating devices having a definite displacement of phase.
Of course when two or more sources of alternating E. M. F. are mechanically
connected together, the relation of their phase is determined by their mechanical
connection. This invention therefore comes into application, where the said sources
are not rigidly connected mechanically together, but are free to set themselves in
relative phasal positions, determined by the mutual reaction of their currents and
fields. It will be seen that the invention comprises as an element, a triangle of
forces, consisting of three sources of alternating electromotive force or counter
electromotive force, connected together in closed circuit, which by their mutual
reaction assume a definite phase relation to one another and form a stable system.
In the case of a larger number of forces, connected in closed circuit, stability is
given by dividing the resulting polygon of forcos into triangles of forces.
An important feature of this invention is, that when two or more sources of
single phase alternating electromotive force are connected together in the manner
described, each of said sources may independently supply single phase alternating
circuits in addition to its function of supplying polyphase currents in conjunction
with the other source or sources. In that case the single phase may or may not
constitute a part of the polyphase system.
In the accompanying drawings, Fig. 1 is a diagrain of a systein of electric supply
and distribution, embodying my invention, showing three single phase generators,
each supplying a single phase alternating circuit, and operating in conjunction to
supply polyphase currents to a part of the system. Fig. 2 is a diagram of a system
wherein sources of counter electro-motive force are used, in part, in place of
generators. Fig. 3 is a diagram showing the connections of four sources of alternating
electo-motive force with a phase controller connected to the junction of said
forces and determining the relative phases thereof. Fig. 4 is a similar diagram
showing the use of a generator as a phase controller. Fig. 5 is a diagram showing
the interposition of a transformer in the circuit the arrangement being otherwise
similar to that of Fig. 2. Fig. 6 is a diagram of another arrangement of
the system in which two machines feed independent circuits, and a third
machine assists in feeding such circuits and at the same time acts as a
phase controller for the other machines. Figs. 7 and 8 are diagrams showing the
application of the induction motor, to a system having but two generators.
Figs. 9-13 represents geometrically the relation of the electro-motive forces in
systems embodying our invention.
We will first explain the general theory of our invention in connection with
Figs. 9-13.
When three sources of alternating electro-motive force generated by
independently driven machines are connected in closed circuit we may represent the
conditions in such circuit by a triangle, whose sides are proportional in length to
the magnitude of the corresponding electromotive forces and correspond in
direction to the phases to such electromotive forces. Thus Fig. 9 may represent
the conditions in a circuit having three such generators of equal electromotive force.
The triangle of forces thus formed is therefore an equilateral triangle and the sides

page_text: and their corresponding electromotive forces are displaced by an angle of 120°.
Again in Fig. 10 tho sides are taken proportionally to the three electromotive
forces, in closed circuit said forces being so proportioned that one is substantially
1.4 times that of the other two, which are equal to one another. This makes the
two later forces 90° apart. So in any triangle representing three forces in closed
circuit we can fix the angular displacement of the sides of the triangle, and there-
fore the relative phases of the corresponding forces by properly proportioning the
sides of the triangle, that is the magnitude of such forces.
When four electro-motive forces are connected in closed circuit, then as indicated
in Fig. 11, the condition of fixing the magnitudes of the electromotive forces
evidently does not at the same time and of itself, fix the relative phases but if we
add the additional condition of fixing the length of one of the diagonals, the angles
between the sides at once become fixed and definite. So in Fig. 12, by fixing the
length of two diagonals of a five sided system, we get a stable arrangement. In
fact this procedure simply consists of splitting up the polygon into triangles, which
are themselves necessarily stable.
In place of the above procedure we may limit the angles of one or more of the
diagonals of the polygon. Thus in the case of the triangle in Fig. 9, we can
suppose the sides ab to be of given length by condition, and the third side to
contain an induction motor, which fixes the angle between this third side and the
two given sides. So also in Fig. 13, we may fix the relative angles of the sides of
the five sided figure by means of an induction motor, having coils arranged so as to
be responsive to the phases on said sides, as hereinafter explained.
Referring now to application of my invention A, A1, A2, Fig. 1, represents three
independently drivon alternating current generators of the single phase type
feeding incandescent lamps L, L, L, etc., in multiple or multiple serios through
transformers connected between the circuits 1-2, 3-4, 5-6, leading from the
respective generators. Said generators have their field magnets excited from any
source of continuous currents, as from separate exciters E, E, E and are indepen-
dently regulable at R, R¹, or automatically regulable, as by a magnet K responsive
to the potential across the mains and acting to maintain or increase the electro-
motive force when the current increases. 7, 8 and 9 represent the conductors
which connect the machines A, A1, A2, in series according to our invention and
between these conductors I may obtain three phase currents for the operation of
multiphase motors. At M is a multiphase induction motor fed by a three phase
transformer T suitably connected between themains 1-2 and 10; the main 10 leads
from the connection 9 between the machines A1, A2, that is, the mains 1, 2 and 10
are leads taken from the connections 7, 8 and 9. In the same manner M¹ represents
a multiphase induction motor, and M² a inultiphase synchronous motor, the latter
having a separate exciter E3 and being supplied with three phase currents without
transformation, between the leads 11, 12, 13, which are branches from the
mains 5-6 and the main 12 leading to the connection 8 between the machines A, A¹.
It is thus easily possible to employ a number of single phase alternating current
generators while in ordinary use in a station, to obtain multiphase currents, such
as three phase currents, for the operation of multiphase currents upon
the system,
without the use of special apparatus, it being only required to make the counec-
tions 7, 8 and 9, indicated, and run a third circuit or conductor, such as 10 or 12,
connected properly as shown.
It is not necessary to have three generators in a station to obtain such polyphase
currents, for, as shown in Fig. 2, two synchronous alternating current motors M,
and M2, may have their armatures connected in series directly by the brushes, or
through transformers, between, the mains 1-2 going from the station, and a third
circuit 5 led to the connection 17 between the motors. By proper excitation of
these synchronous motors, they can be made to change the phase relation of the
potentials on the leads 1, 2, from 180° to 120°-and supply the intermediate main
with a potential 120° from that of each of the lines 1 and 2. This connection
permits me to obtain true three phase currents between the mains 1, 5 and 2, and

page_text: such an arrangement has an advantage over that shown on Fig. 1, in that but two
conductors need to be led to the place of distribution, and from a connection between
two alternating current motors in series, as shown, may be led a third conductor 5
going to the multiphase motors of the system. These motors, can, of course, be
used to supply power, or may be rotary transformers, in addition to their use as
specially connected apparatus for obtaining multiphase currents. The motors, M, M²,
must of course be brought to synchronous speed by any suitable starting
apparatus, as in the case of any single phase motor. The incandescent lights L will
be connected through the mains 1-2 as the potential or their terminals can be
maintained constant by varying the generated potential at the station A, while the
multiphase motors, as M, in circuit with the transformer T¹, will be supplied from
all three circuits.
In Fig. 5 are shown two motors connected in series between the terminals of the
secondary of a transformer T, and three leads taken therefrom, a lead 1 from the
brush B, a lead 2 from the brush B¹, and a lead 3 from a connection joining
the brushes B2, B3. The machines A, M, M² have the same relation as do the
generators A, A³, A³, Fig. 1 or the machines A, M, M2, Fig. 2, in that they are
connected in series, but in the present instance there is an intermediate transformer,
or in other words, the series connection of the three machines is effected indirectly
through a transformer. This arrangement enables me to obtain three currents
between the leads 1, 3 and 2, and of course these currents have the potential of the
secondary of the transformer T and therofore are available by supplying multiphase
currents to motors in a limited area, as in a factory or block.
In Fig. 6 a modified arrangement of generators for obtaining both single phase
and multiphase currents is shown. The generator A delivers currents having a
potential the same as that of the machines A1 and A2. The generator A¹ feeds a
transformer T, the generator A² a transformer T¹, and the generator A feeds both
transformers in series, and thus supplies energy to both circuits 1-2, 3-4, while the
machine A¹, A2, feed said circuits independently and
may therefore be
independently regulated to maintain the desired potential of the generated currents
in said circuits. Each generator has its field magnets excited from any suitable
source of current E, independently regulable at R, R¹, R². The transformers T and
T¹, of course deliver single phase currents to the mains 1-2, 3-4 for incandescent
lights. Multiphase currents for the operation of motors are obtainable from the
two transformers T2, T3, whose primary windings are in series and their free
terminals connected to the brushes of the machine A, while the conductor 9 leads
from the common joint of these transformers to the conductor 8 uniting the machines
A¹, A².
It may be stated that the two generators A1, A2, could not be connected
in series without the generator A in this circuit, as the one machine would soon
entirely neutralize the action of the other, but the connection of the third
generator A in the manner shown prevents this effect by maintaining the potential
on the terminals of the machines A¹, A².
To obtain quarter-phase currents, that is, two currents differing by 90° in time
period, I have devised the arrangements shown in Figs. 3 and 4. It is not
possible to connect two or four independently running similar alternating current
generators in series unless some means are provided to prevent their changing
their mutual change relation. Such means are herein provided as follows :
A, A1, A2, A³. Fig. 3, represents four alternating current generators connected
in series as indicated, each having, if desired, its own independent circuit 1-2,
3-4, 5-6, and 7—8. 1 is an induction motor having a coil Q connected between
the conductors 13-15 joining the machines A, A1, A2, A³ respectively, within the
influence of these coils is mounted a closed circuited armature such as is used
with an induction motor. This induction motor connected as described, establishes
the phase relations of the four generators A, A1, A2, A³. The coils Q, Q1 being
similar in every respect and being placed at an angle of 90°, as shown, the effect
will be to maintain a quarter phase relation between the said generators, and any
departure from this relation will be counteracted by said induction motor.

page_text: The coils Q, Q1 are, as shewn, set at right angles and are of an equal number
of turns. Hence the counter electro-motive forces developed in these coils will
be at right angles and equal in value thereby determining the polygon of electro-
motive forces by the value of the angle of the two diagonals.
This motor also serves at the same time to distribute the load of the generators,
that is, if the load on one generator is in excess of that of the other, a
certain amount of energy will be transferred through the induction motor to
compensate to some extent for this difference of lead. Fig. 13 may exemplify the
application of the same principle to five generators connected in closed circuit.
An induction motor having five inducing coils, is connected respectively to the
junctions of said generators, the other terminals of the coils leading to a common
connection. These coils will, by their mutual reaction through the rotary coil of
the induction motor, establish the relative phases on the several sides of the
circuit.
.
In Fig. 4, as shown, the four generators may be maintained in stable equilibrium
in closed circuit by means of a fifth generator placed in the diagonal of the polygon
of which said four generators form the sides. Here the length of each side of
the polygon and the length of the diagonal may be taken as proportional to the
electro-motive forces of the corresponding generators, the said lengths being
definite the resulting polygon is definite and stable. Fig. 7 shows how two
alternating generators may be connected in series by means of another machine
having the functions of the machine I in Fig. 3. Thus, in Fig. 7, A and A¹ are
two alternators having it may be their own independent circuits at t, and t,
arranged to supply currents of different phase between the mains 1, 2, 3. A
coil on the machine I is connected between the conductor 7 and the conductor 5,
the latter being the intermediate conductor leading from the lead 6 between
the two machines A, A' to tho junction of the primaries of the transformers T
and T3. Another coil Q1, connected between the conductor 4 and the intermediato
conductor 5 is placed at such an angle with relation to the coil Q as corresponds to
the desirod displacement of the phase of the two currents. Within the influence
of the coils Q, Q' is replaced the revolving magnetic structure or armature I. The
coils Q, Q will establish the phase relations on the several sides of the circuit by
reason of their mutual reaction through the medium of the armature I, which acts
as a roter of an induction motor.
. In Fig. 8 an arrangement is shown whereby the coils Q and Q' are at right angles
to each other or displaced at 90°, and the phase from the currents A and A¹ will
therefore also differ by 90°, that is, they will be quarter phase currents, and be
supplied to a system through transformers T2 and T3 as before, while each machine
may like-wise have its own individual circuit, as T, T, and be independently regulated.
The winding of the coils Q and Q: may be modified if their angular displacement
is maintained. Thus, in Fig. 8 the coil Q₁ has its terminals connected to the onter
mains 4 and 7, while from its center connection is made to the middle conductor 5
through the coil Q. Any extra energy or rise of potential in either half of the
coil Q, coming from either machine, A, A¹, will be instantly transferred inductively
to the inner revolving magnetic structure or armature and by it carried to the
coil Q and delivered between the machines A, A1, thus dividing the energy between
the two machines and maintaining a phasal difference between the generated
currents corresponding, as before, to the displacement of the coils Q, Q¹.
Having now particularly described aud ascertained the nature of our said inven-
tion (as communicated to us from abroad) and in what manner the same is to be
perforined, we declare that what we claim is :-
1. The method of supplying polyphase currents from a plurality of windings
whose phase relation is otherwise undetermined, which consists in so connecting
the windings that thoir mutual reactions will establish and maintain a polyphase
relation between the electomotive forces generated therein, and carrying current
from a plurality of said windings to feed a polyphase translating device.

page_text: 2. The method of generating polyphase currents which consists in running the
main windings of a plurality of single phase alternating current dynamo electric
machines, of which one at least is a generator, on a closed circuit, causing the
relations between the machines to displace the phases of the different electro-
motive forces, and delivering a current from a plurality of said machines to a
translating device.
3. The method of obtaining polyphase currents, which consists in generating a
plurality of single phase electro-motive forces by sources each of which is free to
arrange itself in any desired phasal relation with the other sources causing the mutual
reactions of the sources, by reason of their electrical interconnection, to maintain
a polyphase relation between the said electro-motive forces, and conveying current
from said sources to a distribution system.
4 The method of maintaining a desired phase relation between a plurality of single
phase alternating current dynamo electric machines, otherwise free to arrange
themselves in any phase relation whatever, which consists in causing the counter
electromotive force of an alternating current motor to react upon a closed circuit
containing said machines, in such a way to control their phasal relations.
5. The herein described method of obtaining three phase currents, which consists
in connecting in series three single phase alternating generators, and deriving
three phase currents from mains taken from points between said generators.
6. The combination with a plurality of sources of alternating electro-motive
force connected in. series, of one or more branch circuits, each containing a source
of alternating electro-motive force, connected across intermediate points of the
circuit joining said first named sources so as to divide the polygon of electromotive
forces into triangles of electromotive forces, and to fix the phase relations.
7. The combination of a plurality of independently driven single phase alter-
nating generators, connected in closed circuit, mains leading from connections
between said generators, and polyphase translating devices supplied by said
mains.
8. The combination of a plurality of independently driven single phase alter-
nating generators, connections interlinking said generators in said circuit, and
determining the relative phases of the same, mains leading from said connections,
and polyphase translating devices supplied by said mains.
9. The combination of a plurality of sources of single phase alternating electro-
motive force, connected in closed circuit, mains connected to said sources, and
polyphase translating devices connected to three or more of said mains.
10. The combination of a plurality of alternating current dynamo electric
machines, greater in number than two, connected in closed circuit, one at least
of such machines being a generator of electrical energy, and polyphase mains
connected to the junctions of said machines.
11. The combination of three alternating current dynamo electric machines
connected in closed circuit, one at least of such machines being a generator of
electrical energy, and polyphase mains connected to the junctions of such machines.
12. The combination of three single phase alternating generators, connected in
closed circuit, mains and translating devices supplied by one or more of such
machines acting individually, and polyphase translating devices supplied by all of
such machines acting collectively.
13. The combination of sources of a plurality of alternating electromotive forces
free to arrange themselves in relative phasal relation, and electrical connections
interlinking such sources in a closed circuit and polyphase mains leading from said
circuit to a distribution system, the number of the electro-motive forces and the
manner in which they are interlinked being such that said electro-motive forces can
combine only in a fixed and stable phasal relation, and preserve a desired polyphase
relation between the electromotive forces at different positions of the connecting
closed circuits.
14. The combination of a plurality of single phase alternating generators, mains
leading from the terminals of one or more, of said generators translating devices

page_text: between such mains, connections between such generators, interlinking them
in closed circuit, mains leading from such connections, and polyphase translating
devices between mains leading from three or more different portions of said closed
circuit.
15. The combination of a plurality of alternating current dynamo electric
machines capable of running independently, greater in number than two, and
connected in a closed circuit, and leads from a plurality of intermediate points of
said circuit to a translating device.
16. The combination of three or more dynamo electric machines of the alternating
current type, capable of running independently, and connected in a closed circuit
in such a way that their mutual reactions cause their electro-motive forces to
combine in a fixed and stable phasal relation, and to, preserve a desired polyphase
relation between different points of the closed circuit, and connections leading
from intermediate points to a multiphase distribution system.
17. The combination with four or more sources of alternating electro-motive
force connected in closed circuit, of one or more additional sources of alternating
electro-motive force connected across said circuit at such points that each two
of the original sources is in series with one of the additional sources, whereby the
polygon of electro-motive force formed by the original sources is divided into
triangles of electro-motive force.