Improvements in Systems of Electrical Distribution.
Year: 1895

page_text: Date of Application, 9:h Feb., 1895-Accepted, 24th May, 1895
COMPLETE SPECIFICATION.
Improvements in Systems of Electrical Distribution.
I, JAMES DEVONSHIRE, Secretary of The British Thomson-Houston Limited
of 38 Parliament Street, Westminster, in the County of Middlesex, (a communi-
cation to me from abroad by Charles P. Steinmetz of Schenectady, County of
Schenectady, State of New York, United States of America) 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 :-
This invention relates to improvements in systems of electrical distribution by
alternating currents. The systems now in use for this purpose may be divided
into single phase systems, in which the energy is distributed in the form of
alternating single phase currents; and multiphase systems in which the energy is
distributed by two or more alternating currents, differing in phase.
This invention while partaking of the nature of both of these systems, is more
closely related to the single phase system, as in the normal operation thereof the
energy is transmitted by and in the form of single phase currents only. Associated
with the mains carrying the single phase currents are one or more other mains
which supply to any desired part of the system an alternating electro motive force
which is out of phase with the electro motive forces on the mains carrying the
aforesaid single phase currents. This main or mains in which the out of phase
electro motive force is maintained, do not in the normal operation of the system
supply energy to any substantial extent to the various parts of the system, but
under certain abnormal conditions, will transfer energy from one part of the system
to another. The out of phase main or mains may therefore be termed balance
wires, as they act to some extent to maintain the balance of the system, but when
the balance is effected they are substantially inactive as far as transinission of
energy is concerned.
The invention therefore comprises a set of mains connected to and supplied by
a source of single phase alternating currents, and associated with this set of mains
one or more balance wires on which is maintained an electro motive force out of
phase with the electro motive forces on the single phase mains. At various parts
of the system this third wire is connected with translating devices which require
an out of phase electro motive force for their energization, for example certain
forms of alternating current motors. These motors have some of their coils
connected across the single phase mains, and from these mains, in the normal
operation of the motors, is derived the energy which actuates them. Other coils
of the motors are connected to a balance wire and are supplied thereby with an
out of phase electro motive force. In the normal operation of the system, that is,
when the load throughout the system is normal, including the load on the motors,
then the motors will derive substantially all their operating energy from the single
phase mains, and the balance wire while maintaining an out of phase electro
motive force on the coil to which it is connected does not supply any substantial
amount of the energy which is converted into mechanical energy by the rotation of
the motor. Under these circumstances the system becomes substantially a single
phase system, and is capable of being regulated and of carrying single phase
translating devices with the same facility as the ordinary single phase system.
There being in such normal operation, only one wave of current or energy that is
actually concerned in the production, distribution and conversion of the mechanical
energy into electrical energy and back again, I term this system monocyclic.

page_text: Comparing this system with an ordinary multiphase system it is to be noted that
in the multiphase system there are three or more mains carrying two or more
alternating currents of different phase each of which supplies a substantial part
of the energy required for the normal operation of the multiphase translating
devices, and in general the energy transmitted is about equally divided between
the several currents. In the case of the monocylic system, however, as herein
described, only two of the mains and the single phase alternating current carried
thereby, are instrumental in the distribution or transmission of energy in the normal
operation of the system. The other main or mains in such normal operation
supply an out of phase electro motive force but do not have any substantial part
in the actual transfer of energy. This result is accomplished by adjusting the
relation between the impressed electro motive forces, counter electro motive forces
and resistances, both inductive and non-inductive, of the several circuits. In an
ordinary multiphase system this relation is such that in the normal operation of
the multiphase translating devices the counter electro motive force developed in
each branch or circuit in such devices is considerably less than the impressed electro
motive force existing in such branch, or circuit. The consequence of this is that
in each of such circuits a current will flow, consuming energy, and this energy is
drawn from all of the mains. In the monocylic system, however as herein
described, the impressed electro motive force in one or more of the branches or
circuits of the translating devices is made substantially equal to the counter electro
motive force which is generated in such branch or circuit in the normal operation
of the devices, consequently practically no current will flow in such branches or
circuits, the electro motive forces therein being practically balanced. Under
variations of load above or below the normal, this balance will no longer exist
and the balance wire will then be traversed by a current. Thus in the case of an
overload in question, the counter electro motive force will fall below the impressed
electro motive force in the branch connected to the balance wire so that a current
will result in the direction of the impressed electro motive force, that is, the
device will absorb energy from the balance wire. On the other hand, in the case
of an abnormally light load on the translating device the counter electro motive
force in such device will rise above the impressed electro motive force and current
will flow in the direction of the counter electro motive force, thus supplying energy
to the balance wire. The balance wire thus acts as a possible means for trans-
ferring and equalizing the load throughout the system.
The out of phase electro motive force on the balance wire may be derived from
the same machine that supplies the alternating current to the single phase mains,
or it may be derived from a separate machine. It is in fact immaterial what means
are employed to maintain the out of phase electro motive force whether it is by
the action of a source associated with the main source of single phase current-or
of a source entirely distinct therefrom or by the action of one or more of the
translating devices themselves. Thus as I will bereinafter point out, certain classes
of translating devices, such as motors having displaced coils, are capable of
supplying the out of phase electro motive force by their normal operation, while
deriving their operating energy from the single phase mains.
The invention lies not so much in the type or arrangement of apparatus employed,
as in the proportioning of the forces acting therein, and of the resistances opposed
to such forces, so as to bring about a normal condition of static equilibrium or
balance, as regards the balance wire and the parts immediately connected
therewith.
Figure 1 is a diagram of a system of distribution to which this invention is
applicable, the source of out of phase electro motive force being shown as
additional to, but associated with, the main source of a single phase alternating
currents.
Figure 2 is a diagram of a system similar to that shown in Figure 1, the out of
phase electro motive force however, being derived directly from the main source of
alternating single phase current.

page_text: Figure 3 is a diagram of a system of distribution in which the out of phase
electro motive force is obtained, not from a source of electric energy, but, by the
action of the translating devices themselves.
Figure 4 illustrates the application of the invention to a system in which the
electro motive forces are 120° apart in phase.
Figure 5 shows a system in which the electro motive force is supplied by a
motor generator, at a distance from the source of the single phase currents.
In Figure 1, G is an alternating generator having a main armature coil g whose
ends are connected to collector rings 1, 2 Associated with this main coil is an
additional coil g', which is angularly displaced, (preferably 90°) with reference to
the main coil, and is connected at one end to an intermediate portion of the main
coil and at its other cud to a third collector ring. Brushes 6162 bearing on
collector rings, are connected to single phase mains 1. 2. A brush *
bearing on collector ring 3, is connected to a third wire 3. The generator G
is shown as compound wound, having one field coil F included directly in
the single phase circuit through a rectifying commutator C, a resistance R
shunting the break of the commutator to prevent sparking. The other field coil F
is energized by a separate exciter E, having a regulating rheostat R' connected to
the exciting circuit of said field coil and serving for manual regulation of the
potential on the single phase mains 1 and 2 in accordance with the load on the said
mains.
The mains 1 and 2 lead to a point or points at a greater or less distance from
the generator G and are connected to and supply translating devices. The
potential on these mains being in general very high, it is of course desirable to
insert potential reducing transformers between the mains and the translating
devices.
4,5 indicates a branch or sub-circuit containing single phase translating devices L
and supplied with a single phase current through a transf.mer 1 connected
directly across the single phase mains 1. 2. Of course in practice there would be
usually a large number of such single phase branch circits connected to the maius
at different points. With reference to such single phase branch circuits as 4, 5,
Figure 1. the system acts in every respect like an ordinary single phase system,
aud change of load on such single phase circuits as 4, 5 Figure 1. is adjusted for
by the compounding action of the series coil F of the generator and by manual
regulation of the separate exciter circuit by means of a rheostat R' precisely as
with the ordinary single phase system. The energy required for the operation of
these single phase translating devices is derived altogether fro the main generating
coil g of the generator G.
7
The supplementary coil gl however, at the same time generates an electro motive
force which is out of phase with the electro motive force generated in the main
coil, and there are thus developed between the third wire 3 and the respective
mains 1 and 2 electro motive forces which are the resultant of the forces generated
in the supplementary coil, and in the two portions of the main coil, and these
electro motive forces will be different in phase from one another, and from that
existing between mains 1 and 2.
At one or more points of the system connections are made to translating devices,
such as transformers or motors, which require for their operation, out of phase
electro motive forces. Thus connections 6 and 7 are shown leading from
mains 1 and 2, and connection 8, from third wire 3, to induction motor M, having
au inducing winding with main and supplementary coils similarly arranged to those
of the generator G, the single phase lines 6 and 7 leading to the main coil m of
the motor, and the balance wire connection 8, leading to the supplementary coil m¹
thereof. These coils may be supposed to act on a closed circuited armature in the
usual manner and when the motor is started from rest the out of phase electro
motive forces, supplied to its angularly displaced coils will furnish the torque
required for starting. When the motor is running a counter eléctro motive force
is developed in all of, its coils, and the counter electro motive force developed

page_text: between lines 6 and 8 and between lines 7 and 8 will be the resultant of the
counter electro motive forces generated in the main and supplementary coils m m².
The direction and magnitude of the current flowing in the several branches or
circuits, of the motor, depends on the relation between the impressed and the
counter electro motive forces in the respective branches or circuits. By properly
proportioning the windings of the generator, or of the motor, or by properly
adjusting the impedance of the several circuits, the effective impressed and counter
electro motive forces in any of the branches can be made substantially equal,
when the motor is running at normal speed and load. Thus in the case of the
motor M, the coil m¹ may have a relatively high resistance or a high self
induction, so as to relatively diminish the effective impressed electro motive force,
or it may have a greater inducing effect, relatively to the main coil than is the case
with the corresponding coil of the generator, or the third wire 3, and connections
may be of relatively high impedance. Any arrangement or adjustment, in fact,
may be adopted that will bring up the counter electro motive force or depress the
impressed electro motive force in the coil m' so as to make them substantially
equal in the normal operation of the motor-while preserving the necessary
excess of impressed over counter electro motive force in the other coil or coils--so
as to enable the necessary flow of current in the last named coils for the operation
of the motor. This peculiar form of induction motor is illustrated and described
simply as one of a variety of arrangements in which the invention of this
application may be embodied; but as appears herein, the invention may also be
embodied equally well in a variety of other arrangements, and I make no special
claim to the construction of the induction motor, since I regard this as a distinct
invention, which is claimed in another application for Letters Patent bearing equal
date herewith No. 2918 95
The motor M is shown directly connected to the mains and third wire, but it is
obvious that tension reducing transformers may be included in the connections if
desired. If the motor is adapted to the same phasal relation of electro motive
forces as are developed by the generator G, the transformers may be arranged as
indicated at T, two transformers t and t¹ having their primary windings connected
respectively between the main 1 and the third wire 3 and the main 2 and said
third wire. Their secondaries are similarly connected to lines 9, 10 and 11
leading to motor M¹, which is similar in construction and operation to motor M,
the windings being so proportioned that, in the normal operation of the motor, the
counter electro motive force developed in the coil connected to third wire 11 is
substantially equal to the electro motive force impressed thereon. Single phase
translating devices L are also shewn connected across in the circuits 9, 11
and 10, 11. With respect to these translating devices, the wire 3 acts substantially
as a balance wire, like the third wire of an ordinary three wire system.
The operation of the system is as follows:-The generator G develops between
mains 1 and 2, a single phase alternating electro motive force which alone is
effective in the operation of the single phase translating devices connected across
said mains. At the same time there are generated between the third wire 3 and
the mains 1 and 2, electro motive forces out of phase with one another, and with
that between mains 1 and 2. Such electro motive forces, delivered to the motors,
enable the same to be started from rest under load and to be brought up to
normal speed. The counter electro motive force thus developed in the branch of the
motors, which is connected to the third wire, then becomes substantially equal to
the impressed electro motive force in such branch, while the counter electro
motive forces in the branches connected to the single phase lines remaining less
than the impressed electro motive force from said mains-current will flow from
the mains sufficient for the normal operation of the motors. If then any motor
becomes overloaded the counter electro motive force in its out of phase branch will
fall below the impressed electro motive force, and energy will again be delivered
to the motor through the third wire until the overload is removed. This extra
energy will be derived either from the generator, or from any other motor which
t

page_text: is connected to the same system and is not equally overloaded. And if any one
of the motors is underloaded, the counter electro motive force in its out of phase
branches will rise above the impressed electro motive force and the motor will
deliver energy to the third wire, such energy being derived from the single phase
mains. Thus the third wire under such abnormal conditions will transfer energy
between the motors and the generators-and between the several motors-acting.
as a balance wire for the whole system.
It will be seen that the third wire acts in relation to all the devices to which it
is connected, as a possible means of supplying energy when needed, or of
transferring surplus energy from one part of the system to other parts, and this
energy is of course supplied and transferred by and in the form of alternating
currents, out of phase with those on the single phase mains. Such currents are
however, comparatively small and incidental, compared with the current on the
single phase mains-and would generally be momentary, or at least of short
duration. The third wire may therefore be comparatively small in cross section.
The main advantage of the system however, lies in the fact that, owing to the
relative unimportance of the incidental currents flowing in the third wire the
generator may be regulated solely with a view to the maintaining of proper
potential on the single phase mains-and these mains alone being substantially
concerned in the transmission of energy-the difficulty of balancing up the load
between several circuits does not arise.
In Figure 2 is represented a system of distribution wherein the generator G'
has two sets of angularly displaced coils gg', which taken together, in series,
develop a resultant single phase of electro motive force on the mains 1 and 2,
while acting individually they produce out of phase electro motive forces between
mains 1 and third wire 3, and between main 2 and third wire 3. The generator is
shown as separately excited with means for manual regulation-but it will be
understood that it may be compound wound like the generator indicated in
Figure 1. Single phase translating devices L may be supplied by transformers
connected directly across the single phase mains. The generator coils are indicated
as displaced 60°, giving 60° angle of phase difference between circuits 1, 3,
and 2, 3. From these electro motive forces 60° apart-appropriate transformers
may develop any desired phase relation-or the electro motive forces may be
applied to motors especially adapted to work with this particular phase relation.
Thus motors M, M, M are indicated with reversed coils connected to the third
wires of the several sub-circuits. In each case however, the windings and
impedance are so proportioned as to give an approximate balance between the
counter and impressed electro motive forces when the motor is in normal
operation.
The sub-circuit 17, 18, 19 containing motor M*, is also shown as containing
lamps L³ connected across the single phase sub-mains.
The out of phase electro motive force, in the system shown in Figure 1, is
derived from a source supplementary to, but associated with, the source of single
phase current. In the system shown in Figure 2, the out of phase electro motive
force is derived from the same coils that generate the electro motive force on the
single phase mains. It matters not however, how this out of phase electro motive
force is developed-whether it comes from the same machine as the single phase
currents, or from another machine.
If the out of phase electro motive force comes from a separate machine from
that generating the single phase current, such separate machine may be either a
generator a motor, that is, it may derive its operating energy either from a
separate and additional source of power, or from the single phase lines themselves.
In fact, in the system above explained, each motor connected to the system acts
to generate in the third wire connections an out of phase electro motive force,
opposite and approximately equal to that impressed by the generator. It therefore
becomes obvious that I may omit the connection of the third wire to the

page_text: generator, leaving it to connect only the motors among themselves. The third
wire will then still act as a balance wire among the several motors. Such a
system is represented in Figure 3, wherein G2 is the generator which in this case
would be of the strict single phase type, delivering a single phase alternating
current to mains 1, 2, and having its field coil F³ excited by separate exciter E³.
Means for automatic or manual regulation may be provided, as before, to regulate
the potential on the single phase mains, in accordance with the load thereon.
Single phase translating devices L are supplied by said mains, through potential
reducing transformers, as indicated at T³.
Two or more alternating motors M7 M8 have a part of their coils connected
across the single phase mains, and their other coils which are angularly displaced
with reference to the former-are connected together by the third wire 3. In said
figure, these connections are effected, in each case, through the intervention of
transformers. In case the motors are adapted to operate with similar phase relations
these transformers may be of the kind indicated in Figure 3, being similar to the
transformer arrangement shown at tt', Figure 1. It will now be seen that the multi-
phase motors, so arranged, will serve to maintain, when in normal operation, and out
of phase electro motive force between the lines 1 and 3, and 2 and 3. Furthermore,
any one of the motors having been started, it will supply the out of phase electro
motive force required for starting any one of the other motors, a momentary out
of phase current flowing through the third wire until the motors reach the
normal relation of speed. Transfer of energy between the several motors will
take place in accordance with the
::.
1
capiatutu.
The first motor of the system to start in operation must of course be started by
some extra means or special means, but such not being a part of the invention, and
there being various well known ways of accomplishing it no special means for this
purpose are shewn.
The out of phase electro motive forces may also be generated at a point distant
from the source of single phase currents, by a generator or motor generator,
located at such distant point and connected to the mains and to the balance wire-
the latter being in that case, connected to the various multiphase translating devices,
but not connected back to the generator. Thus in Figure 5, a system of distribution
is shewn in which mains 1, 2 supplied with single phase current by generator G³,
are connected also to the coils of a generator or motor-generator M.G.-at a
distance from the generator G 3. The machine M.G. may be driven by an
independent source of power, so as to constitute a generator or it may derive its
operating energy from the single phase mains. It is connected to balance wire 3,
arranged to generate out of phase electro motive forces between the mains 1 and 2
and balance wire 3. Alternating current translating devices, such as motor M are
connected to said mains and balance wire-and the normal condition on said balance
wire is one of equilibrium, as before.
The invention is readily applicable to the ordinary three phase system-by
properly proportioning the resistances or impedances of the several circuits, or by
making the several coils of the generators or of the motors, slightly unequal in
effect. Such a system is shewn in Figure 4. G being a three phase generator,
connected to mains 1, 2 and 3. Single phase translating devices are included
between two of the mains 1 and 2-and multiphase devices are connected to said
mains and also to the third wire 3. The condition of balance on this third main
may be effected by making the coil g³ of the generator which is connected thereto,
of less effect than the coils gl g² connected to the mains 1 and 2, or it may be
accomplished by making the third main 3 of high resistance, or as indicated in the
drawing both of these expedients may be adopted in the same system.
It will be understood that when the term "connected" is used in this Specification,
it must be taken in a broad sense, as including connections through transformers
as well as direct connections.
While I have spoken of the translating devices which are connected to both the

page_text: mains and the balance wire as "multiphase" translating devices I wish it to be
understood that they are not multiphase except as regards the electro motive forces
acting therein. The translation of energy is substantially of a single phase
character and the devices are, strictly speaking, when used according to this
invention, single phase translating devices,-generating out of phase electro motive
forces and this is the sense in which the term "multiphase translating devices" is
herein intended.
It is obvious that where two mains are shewn any number of mains may be
understood, and similarly a third wire may be typical of any number of balance
wires, which may be associated with the same or different mains.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed 1 declare that what I
claim is :-
1. In a system of electrical distribution the combination of single phase mains,
carrying a single phase alternating current-a third wire-means for developing
between said third wire and mains, electro motive forces out of phase with that on
the single phase mains, and translating devices connected across said single phase
mains and also connected to said third wire-the energy required for the normal
operation of such translating devices being derived substantially from said single
phase mains.
2. The combination with a multiphase translating device of single phase mains
connected thereto and supplying same with substantially all of the energy required
for its normal operation-and a third wire also connected to said multiphase
translating devices and impressing thereon an alternating electro-motive force, out
of phase with that on the single phase mains, but supplying substantially no energy
to said translating device, in the normal operation thereof.
3. In a system of electrical distribution the combination of single phase alternating
mains, one or more balance wires, between which and said mains, alternating electro
motive forces are maintained out of phase with the electro motive force on said
mains, and multiphase translating devices having coils connected to said single
phase mains, and deriving therefrom substantially all the energy required for the
normal operation of the devices-and having other coils angularly displaced with
reference to aforesaid coils-and connected to said third wire, but deriving
substantially no energy therefrom in such normal operation.
4. The combination of two or more multiphase devices, which in their normal
operation develop in different portions thereof-electro motive forces of different
phase, of single phase mains connecting portions of said devices and serving for the
normal transfer of current to or from the same and a balance wire connecting
other parts of such devices of different phase of electro motive forces, the electro
motive forces in said balance wire being in the normal operation of the devices,
substantially balanced.
5. The method of operating multiphase translating devices which consists in
supplying to some of the coils thereof, a single phase alternating current of
sufficient energy for their normal operation, causing said current to induce in other
coils of said devices, electro motive forces out of phase with the electro motive
force of such single phase current, and impressing on such other coils, an
alternating electro motive force opposed and substantially equal to the counter
electro motive force developed in the normal operation of the devices.
6. The method of operating multiphase translating devices which consists in
supplying to a portion of such device, by a single phase current, energy sufficient
for the normal operation thereof and maintaining on another portion of such device
an electro motive force out of phase with that of said current.
7. The method of operating a multiphase translating device having different
portions or branches in which in normal operation, counter electro motive forces of
different phase are developed, which consists in impressing on said different portions
or branches electro motive forces, respectively opposed to said counter electro

page_text: motive forces the impressed electro motive force being greater than the counter
electro motive force in one or more of the portions-and substantially equal to the
counter electro motive force in another portion.
8. The combination with two or more multiphase devices, each having
relatively displaced coils, of mains connecting corresponding coils in the
several devices and serving for the normal transfer of energy to or from the
same and a third wire connecting coils displaced relatively to aforesaid coils
the electro motive forces developed by said devices in said third wire being opposed,
and approximately equal in the normal operation of the devices.
9. The combination with a multiphase motor having relatively displaced coils, of
single phase mains connected to a portion of said coils and supplying substantially
all of the operating energy of the motor in the normal operation thereof and a
third wire connected to a portion of said coils displaced relatively to aforesaid
portion and impressing thereon an electro motive force substantially equal to
the counter electro motive force developed therein, in the normal operation of the
motor.
10. In a system of electrical distribution the combination of single phase mains,
carrying a single phase alternating current--a third wire-means for developing
between said wire and mains, electro motive forces out of phase with that on the
single phase mains, single phase translating devices supplied by said mains, and
multiphase translating devices connected across said single phase mains and also
connected to said third wire-the energy required for the normal operation of such
multiphase translating device being derived substantially from said single phase
mains.
11. In a system of electrical distribution the combination of single phase mains,
single phase transmitting devices connected across said mains, a generator of single
phase alternating currents is connected to said mains, means for regulating said
generator in accordance with the load on said single phase mains, a third wire,
means for developing between said third wire and mains, electro motive forces out
of phase with that between said mains, and multiphase translating devices connected
across said mains and deriving substantially their whole normal operating energy
therefrom and also connected to said third wire.
12. In a system of electrical distribution in which single phase and multiphase
devices are connected to the said mains, the method of distribution which consists
in supplying through said mains, single phase alternating currents of sufficient
energy for the normal operation of all such devices, and regulating the potential on
said single phase mains in accordance with the load thereon.
13. The combination of three or more lives, means for supplying said lines with
out of phase electro motive forces, translating devices connected to said lines and
generating out of phase counter electro motive forces, the ratio of counter electro
motive force to impressed electro motive force being less on one or more of said
lines than it is on the others.
14. In a system of electrical distribution the combination of three or more lines,
means for developing between said lines out of phase electro motive forces, a
translating device having different portions in which out of phase electro motive
forces are generated, such portions being connected respectively to said lines, and
the ratio of counter electro motive force to impressed electro motive force being less
in one or more of the portions than it is in the others.
Dated this 8th day of February 1895.
JAMES DEVONSHIRE.