Improvements relating to the Generation and Distribution of Alternating Electric Currents for Light and Power.
Year: 1897

page_text: Date of Application, 30th Mar., 1897.
Complete Specification Left, 30th Dec., 1897-Accepted, 12th Mar., 1898
Improvements relating to the Generation and Distribution of
Alternating Electric Currents for Light and Power.
I, JASPER WETTER, Patent Agent, of 37 & 39, Essex Street, Strand, in the
County of London, do hereby declare the nature of this invention as communicated
to me by the Elektrizitats-Aktiengesellschaft (vormals Schuckert & Co.), Manu-
facturers, of Nurnberg, Germany, to be as follows:-
The ordinary single-phase system of distribution is most suitable for electric
lighting, but as the single phase motors generally known cannot start at full load,
its application has been very limited. On the other hand, the polyphase system
is most suitable for the transmission and distribution of power, owing to the high
starting power of polyphase motors and the equal distribution of the load on the
different branches. If, however, the polyphase system is used to supply current
for lighting purposes, the distribution becomes unequal and consequently also the
luminosity of the lamps in different branches, or it is necessary to adopt compli-
cated regulating devices.
The present invention has for its object, to combine the advantages of the single
phase with those of the polyphase system, so as to be specially suitable for a mixed
distribution of electric current for lamps and motors.
For this purpose the armature of the generator is provided with two windings,
ns in the case of a two-phase armature, the second phase lagging 90° behind-the
first. The beginning of one winding is joined on to the middle of the other, aud
the two windings, or the electromotive forces produced in the same, have a pre-
determined ratio to each other.
If in the accompanying diagram Fig. 1, ab represents the electromotive force
of the main winding, and if the supplemental winding - be equal to one half
of ab, the resulting electromotive forces and bd will have a difference of phase
equal to 90°.
The conductors starting from the points a, b and d are in this case to be con-
nected with two-phase motors, while lamps only are to be connected with the two
external conduits coming from a and b.
If, however, the supplemental winding is made of such a size, that it produces
an electromotive force --f-a-b, lang a the resulting electro-motive forces a-e
and will lag 120° one behind the other and forth two phases, while the electro-
motive force of the main winding, ab, forms the third phase of a three-phase
motor.
The combination of the electro motive forces a-band.cf may be considered
as a combined one-phase system, in which the main winding supplies the whole
of the lighting current and a part of the power current, while the supplemental
winding supplies the remaining part of the power current.
Fig. 2 is a diagram showing the distribution of current for light and for three-
phase motors. A is the main winding, the ends of which are connected with a

page_text: and b, which are the starting points for the two external or main conduits. The
supplemental winding B is joined with one end to the middle of A and with the
other to c, from which the third, that is to say the weak or intormediate conductor
starta.
The three-phase motors are connected with all three conductors, as shown at C,
Fig. 2; the fighting current is derived from the two external conductors only, as
shown at D, Fig. 2.
Another method of attaining the same object is indicated by Fig. 3. Instead
of using the main conduit for the simultaneous supply of lighting and power ourrent,
two separate windings, A, and Ag, may be adopted, of which A, supplies
current only for lampa and current consumers which require only a single-phase
current, while a supplemental winding B is connected with the middle of the
winding Ag, and the windings A and B thus combined produce together only tho
power current.
The windings A, and A, may be arranged in parallel and joined together with
their ends at the two starting terminals for the two main conductors.
Fig. 4 shows a special example of a three-phase lighting installation, in which
the two groups of lamps need not be loaded equally. The combination of the
generator windings is the same as in Fig. 2, except that the junction between the
supplemental coil B and the main coil A forms also the starting point for
the middle conductor of a three-phase system for the places of consumption for
Lighting current.
Fig. 5 shows another very simple arrangement. In many cases the consumption
of current for power amounts to less than twenty per cent. of that used for electric
lighting, in which case the sectional area of the intermediate conductor may be
less than ten per cent. of that of one of the two main conductors.
If, in the case of generating stations whose area of consumption is not at too
great a distance, the dimensions of the main winding A., are calculated for high
pressure, and those of the supplemental winding B, for low or working pressure,
all three conductors may have the same thickness or sectional area, which is an
advantage as regards the manufacture of cables.
The cost of copper from the generating station to the principal points of distribu-
tion is somewhat higher, but considerable expense will be saved by simplifying
the transformation.
As shown by Fig. 5, the middle conductor is joined directly to a terminal of
the motors, that is to say to the motor starter, whereas ordinary single-phase
transformers are simply arranged between the external high-pressure conductors.
The secondary terminals of the transformers are then connected with the two other
terminals of the polyphase motors. The middle conductor starting from the
secondary generator winding B, may be connected to earth, either directly or
through the intermediary of a resistance, in order to avoid the occurrence of any
high pressure at the corresponding motor terminals.
The same transformers may he utilised for the simultaneous supply of lighting
current with or without the use of an additional secondary coil (which will be
referred to later on).
Fig. 6 indicates a further application of this system. If it is desired, to use only
two conductors for transmitting electricity to a distance, only single-phase
generators A are erected at the power station, and synchronous single-phase motor-
generators in the area of distribution. To the middle of the armature winding A,
of these motors is joined a supplemental winding B, the other end of which is
connected with the middle conductor. These produce a component energy, which
lags 90 degrees behind the principal phase. The composition of the electro-motive
forces and the manner in which light and power current is taken off, are then
exactly as in the arrangements represented by Figs. 1 to 3.
Moreover, the manner of counecting the circuits indicated in Fig. 6, in which
only a single-phase transformer is required for connecting multiphase transformers,
is also applicable in this case, if A, indicates the motor-winding for high pressure

page_text: and B, the generator winding for low pressure. The two windings A, B or
A B may be mounted on one armature.
It is advantageous also to utilise these synchronous motors for producing a lead
of phase in the electro-motive force, to compensate the lag of phase which is pro-
duced by the no-load current for motors or transformers, and by the self-induction
of the circuit.
For this purpose the magnets are super-excited, and the motors are made larger
to correspond.
With all these arrangements, we obtain also the great advantage, that, na in
a single-phase system, the pressure only need be regulated for the consumption of
light, and therefore only the excitation of the magnet; for the supplemental wind-
ing revolves in the same field, in consequence of which the same ratio between the
electro-motive forces of the two windings is always maintained, and thereby a
balanced multiphuse system for working electro-motors is always ensured.
The arrangement of the transformers will be explained with the aid of Fig. 2.
C shows the connections of a three-phase transformer or of three single-phase trans-
formers, while the other methods of connecting transformers imply new simplifica-
tions, in euch case two single-phase transformers being used with three-phase
Diotors.
E indicates two transformers connected exactly in the same manner, as the main
and the supplemental windings are arranged in the generator, which may be called
the T connection, to distinguish it from the V connection shown at F.
At E the main transformer produces one phase, and the resultant of each half
of the main transformer in combination with the supplemental transformer pro-
duces the two other phases.
In the V connection shown at F each transformer receives the full current of
the corresponding phase, which phases are placed at 120 degrees to each other;
the third phase passes through both transformers jointly and produces a resultant
which is placed at an angle of 120 degrees to each of the two other phases.
A further advantage may be derived from the following method of connection.
If the same secondary terminals of a transformer with which motors are connected,
are used also for taking off current for lighting purposes, as at E, fluctuations of
pressure and therefore also of light will occur at each switching in or out, or
whenever the load on the motors changes, which fluctuations are caused by a dis-
placement of phase between current and pressure in inductive circuits. Experi-
ients have shown, that these fluctuations may be avoided by dividing the
secondary coils of the transformer into sections, and using one section of the same
for motors, while the other is used for lighting, as indicated by Fig. 2 G. The
primary coil may also be arranged in parallel and joined by means of separato
connections to corresponding conductors of the distributing network.
Dated this 30th day of March 1897.
FAIRFAX & WETTER,
Agents for the Applicant.
Improvements relating to the Generation and Distribution of
Alternating Electric Currents for Light and Power.
I, JASPER WETTER, Patent Agent, of 37 & 39, Essex Street, Strand, in the
County of London, do hereby declare the nature of this invention and in what

page_text: manner the same is to be performed to be particularly described and ascertained
in and by the following statement:-
The ordinary single-phase system of distribution is most suitable for electric
lighting, but as the single phase motors generally known cannot start at full load,
its application has been very limited. On the other hand, the polyphase system
is most suitable for the transmission and distribution of power, owing to the high
starting power of polyphase motors and the equal distribution of the load on the
different branches. If, however, the polyphase system be used to supply current
for lighting purposes, the distribution becomes unequal and consequently also the
luminosity of the lamps in different branches, or it is necessary to adopt compli-
cated regulating devices.
The present invention has for its object, to combine the advantages of the single
phase with those of the polyphase system, so as to be specially suitable for a mixed
distribution of electric current for lamps and motors.
For this purpose the armature of the generator is provided with two windings,
as in the case of a two-phase armature, the second phase lagging 90° behind the
first. The beginning of one winding is joined on to the middle of the other, and
the two windings, or the electro-motive forces produced in the same, have a pre-
determined ratio to each other. In further describing the invention reference will
be made to the drawings, Figs. 1 to 6, filed with the Provisional Specification.
If in the diagram Fig. 1 ab represents the electromotive force of the main
winding, and if the supplemental winding fd bo equal to one half of a-b, the
resulting electromotive forces a-d, b-d will have a difference of phase equal
to 90°.
The conductors starting from the points a, b and are in this case to be con-
nected with two-phase motors, while lamps only are to be connected with the two
external conduits coming from a and b.
129
If, however, the supplemental winding be made of such a size, that it produces
an electromotive force of=ta, b, tang the resulting electro-motive forces a-c
and will lag 120° one behind the other and form two phases, while the electro-
motive force of the main winding, a-b forms the third phase of a three-phase
notor.
The combination of the electro motive forces ab and c-f may be considered
as a combined one-phase system, in which the main winding supplies the whole
of the lighting current and a part of the power current, while the supplemental
winding supplies the remaining part of the power current.
Fig. 2 is a diagram showing the distribution of current for light and for three-
phase motors. A is the main winding, the ends of which are connected with a
and b, which are the starting points for the two external or main conduits. The
supplemental winding B is joined with one end to the middle of A and with the
other to e, from which the third, that is to say the weak or intermediate conductor
starts.
The three-phase motors are connected with all three conductors, as shown at C,
Fig. 2; the lighting current is derived from the two external conductors only, as
shown at D, Fig. 2.
Another method of attaining the same object is indicated by Fig. 3. Instead
of using the main conduit for the simultaneous supply of lighting and power current
two separate windings, A, and Ag, may be adopted, of which A, supplies
current only for lamps and current consumers which require only a single phase
current, while a supplemental winding B is connected with the middle of the
winding A, and the windings A and B thus combined produce together only the
power current.
The windings A, and A, may be arranged in parallel and joined together with
their ends at the two starting terminals for the two main conductors.
Fig. 4 shows a special example of a three-phase lighting installation, in which
the two groups of lamps need not be loaded equally. The combination of the

page_text: gonerator windings is the same as in Fig. 2, except that the junction between tho
supplemental coil B and the main coil A forms also the starting point for the
middle conductor of a three-phase system for the places of consumption for light-
ing current.
Fig. 5 shows another very simple arrangement. In many cases the consumption
of current for power amounts to less than twenty per cent. of that used for electrio
lighting, in which case the sectional area of the intermediate conductor may be
less than ten per cent, of that of one of the two main conductors.
If, in the case of generating stations, whose area of consumption is not at too
great a distance, the dimensions of the main winding A are calculated for high
pressure, and those of the supplemental winding B, for low or working pressure,
all three conductors may have the same thickness or sectional area, which is can
advantage as regards the manufacture of cables.
The cost of copper from the generating station to the principal distributing
centres is somewhat higher, but considerable expense will be saved by simplifying
the transformation.
As shown by Fig. 5 the middle conductor is joined directly to a terminal of
the motors, that is to say, to the motor starter, whereas ordinary single-phase
transformers are simply arranged between the external high-pressure conductors.
The secondary terminals of the transformers are then connected with the two other
terminals of the polyphase motors. The middle conductor starting from the
Secondary generator winding B, may be connected to earth, either directly er
through the intermediary of a resistance, in order to avoid the occurrence of any
high pressure at the corresponding motor terminals.
The same transformers may be utilised for the simultaneous supply of lighting
current, with or without the use of an additional secondary coil (which will bo
referred to later on).
Fig. 6 indicates a further application of this system. If it is desired, to use only
two conductors for transmitting electricity to a distance, only single-phase
generators A are erected at the power station, and synchronous single-phase motor-
generators in the area of distribution. To the middle of the armature winding A
of these motors is joined a supplemental winding B, the other end of which is
connected with the middle conductor. These produce a component energy, which
lags 90 degrees behind the principal phase. The composition of the electro-motive
forces and the manner in which light and power current is taken off, are then
exactly as in the arrangements represented by Figs. 1 to 3.
Moreover, the manner of connecting the circuits indicated in Fig. 5, in which
only a single-phase transformer is required for connecting multiphase transformers,
is also applicable in this case, if A, indicates the motor-winding for high pressure
and B, the generator winding for low pressure. The two windings A, B or
A B may be mounted on one armature.
It is advantageous also to utilise these synchronous motors for producing a lead
of phase in the electro-motive force, to compensate the lag of phase which is pro-
duced by the no-load current for motors or transformers, and by the self-induction
of the circuit.
For this purpose the magnets are super-excited, and the motors are made larger
to correspond.
With all these arrangements, we obtain also the great advantage, that, as in
a single-phase system, the pressure only need be regulated for the consumption of
light, and therefore only the excitation of the magnet; for the supplemental wind-
ing revolves in the same field, in consequence of which the same ratio between the
electro-motive forces of the two windings is always maintained, and thereby a
balanced multiphase system for working electro-motors is always ensured.
The arrangement of the transformers will be explained with the aid of Fig. 2.
C shows the connections of a three-phase transformer or of three single-phase trans-
formers, while the other methods of connecting transformers imply new simplifica-

page_text: tion, in each case two single-phase transformers being used with three-phase
motors.
E iudicates two transformers connected exactly in the same manner, as the main
and the supplemental windings are arranged in the generator, which may be called
the connection, to distinguish it from the V connection shown at F.
At E the main transformer produces one phase, and the resultant of each half
of the main transformer in combination with the supplemental transformer pro-
duces the two other phases.
In the connection shown at Feach transformer receives the full current of
the corresponding phase, which phases are placed at 120 degrees to each other;
the third phase passes through both transformers jointly and produces a resultant
which is placed at an angle of 120 degrees to each of the two other phases.
A further advantage may be derived from the following method of connection.
If the same secondary terminals of a transformer with which motors are connected,
are used also for taking off current for lighting purposes, as at E, fluctuations of
pressure and therefore also of light will occur at each switching in or out, or
whenever the load on the motors changes, which fluctuations are caused by a dis-
placement of phase between current and pressure in inductive circuits. Experi-
ients have shown, that these fluctuations may be avoided by dividing the
secondary coils of the transformer into sections, and using one section of the same
for motors, while the other is used for lighting, as indicated by Fig. 2 G. The
primary coil may also be arranged in parallel and joined by means of separate
connections to corresponding conductors of the distributing network.
The primary winding may also be arranged in parallel and fead by two branches
to equal conductors of the distributing network.
In current generators, with two windings, both the main windings and the
supplemental windings are calculated for definite capacities of work of the machines.
If now, in an existing plaut, the ratio between the consumption of lighting current
and the consumption of power current in one direction or in another, it is advan-
tageous to provide that the current generators may be adapted to these periodical
variations.
For this purpose one or more single-phase generators may be mounted in the
central station in addition to the existing machines, which single-phase generators
are switched into circuit in case of increased demand for light (for instance in the
evening), parallel to the main windings of the current generators already in motion,
as indicated by Fig. 7 of the accompanying drawings, or in case the consumption
of current for motive power prevails, parallel to the supplemental windings (as
indicated by Fig. 8) or parallel to one of the two resultants, or to both (Fig. 9).
In adopting the method of connection represented by Fig. 9, the single-phase
machine running in parallel with the supplemental winding has only to produce
0.866 of the electromotive force of a phase, which may be effected in a simple
manner by a correspondingly weaker excitation of the field magnets.
The same object may be attained by providing the central station with a double
current generator as a reserve, that is to say, two mechanically coupled single-
phase machines, which, if the demand for light increases are connected at equal
phase (Fig. 10) or if the consumption of current prevails, are connected with their
phases at 90°, as indicated by Fig. 11, and coupled in parallel with the current
generator already in motion.
Having now particularly described and ascertained the nature of the said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is: :-
1. A system of distribution of alternating electric currents for simultaneously
supplying electric lamps with single-phase current and electro-motors with
multiphase current, said system comprising two windings on the dynamo-electric
generators, which differ in phase 90°, viz. a main-winding connected at its ends
with the two main conductors of the single-phase distributing net, and a supple-

page_text: mental winding connected at one end with the middle of the main-winding, while
the other is the starting point of an intermediate conductor which in conjunction
with the main conductors serves to feed the multiphase motors, substantially as
described.
2. In a system of electric distribution as specified above, a dynamo electric
generator having a main winding divided into two separate windings, one of which
supplies only the single-phase current for the two main conductors, while the
other, which is connected in the middle with the supplemental winding, produces
jointly with the latter the polyphase current, substantially as described.
3. A composite system of distribution of single-phase electric current having
generator windings connected as specified by Claim 1, the main winding being
adapted to produce high tension current and the supplemental winding low tension
current, in order that only a single-phase transformer or several single-phase
transformers arranged in parallel may be required for feeding multiphase motors,
substantially as described.
4. A single-phase system of power transmission, comprising synchronous motor
generators each of which has two windings differing in phase 90°, viz. one receiv-
ing current and being fed by the single-phase system, and one generating current
and being connected at one end with the middle of the current receiving winding,
while the other end is connected with the intermediate conductor leading outward,
for the purpose of distributing electric energy to lamps and multiphase currents
in the manner specified by Clause 1.
5. The application of only two single-phase transformers for supplying three-
phase current in the manner described with reference to Fig. 2 E and Fig. 2 F.
6. The subdivision of the secondary windings of the transformers in such a
manner, that one part serves exclusively for loads free from induction, such as
glow-lamps, and the other for inductive loads, such as motors, substantially as
described.
7. In a system of distribution of alternating currents, as specified by Clause 1,
single-phase current generators arranged synchronously and in parallel to the main
windings, or to the supplemental windings differing in phase 90°, or to a resultant
or the two resultants of the main and supplemental windings, for adapting the
output of the machine either to a prevailing consumption of lighting current or to
a prevailing consumption of power current, according to requirement, substantially
as described.
8. In a system of alternating current distribution as specified by Clauso 1, two
mechanically coupled single-phase machines arranged in parallel to the current
generators in motion, either equiphase or with phases differing 90°, for the purpose
of adapting the output of the machines to a prevailing consumption of lighting
current or to a prevailing consumption of power current, according to requirement,
substantially as described.