Improvements in Methods of and Means for Electrical Conversion and Distribution.
Year: 1897

page_text: Date of Application in the United Kingdom, 26th Aug., 1897
Complete Specification Left, 24th June, 1898-Accepted, 26th Aug., 1898
PROVISIONAL SPECIFICATION.
Improvements in Methods of and Means for Electrical Conversion
and Distribution.
1, BENJAMIN GARVER LAMME, C/o., Westinghouse Electric and Manufacturing
Company, East Pittsburg, State of Pennsylvania, United States of America,
Electrical Engineer, do hereby declare the nature of this invention to be as
follows:-
My invention relates to systems of electric distribution involving means for
converting alternating into direct currents and it has for one of its objects to
provide a rotary transformer for converting multiphase alternating currents
into direct currents, which shall operate efficiently and satisfactorily irrespective
of the wave form of the currents supplied to it and the number and character
of the machines which may be coupled in parallel with it.
A further object of the invention is to provide a method and a means whereby
a three-wire direct current system may be supplied with energy from an alternat-
ing current supply circuit at a minimum expense and loss of energy and with
a maximum degree of efficiency.
A further object of the invention is to provide a method and means whereby
direct current motors may be run at different speeds without varying the field
magnet excitation or the applied electromotive force.
A further object of the invention is to provide means whereby a plurality of
different voltages may be secured in connection with an alternating current cir-
cuit and a rotary transformer.
Reference being had to the accompanying drawings,
Figure 1 is an end elevation of a rotary transformer constructed in accordance
with one feature of my invention, the end bearing being broken away and the
armature conductors and commutator being shewn diagrammatically.
Figure 2 is a side elevation of the rotary transformer shewn in Figure 1.
Figure 3 is a diagram illustrating the phase relation and amplitude of the
magnetic fields produced by the armature currents of the transformer shewn in
Figures 1 and 2.
Figure 4 is a diagram illustrating another feature of my invention in con-
nection with a two-phase alternating current system of distribution.

page_text: Figure 5 is a similar view shewing a different form of stationary transformer
and additional direct current circuits.
Figure 6 is a diagram illustrating the invention in connection with a three
phase alternating current system.
Figure 7 is a diagram illustrating two additional features of my invention in
connection with a single phase alternating current system.
Reference being now had particularly to Figures 1, 2, and 3, 1 is a multi-
polar field magnet of ordinary construction, except that the pole pieces 2 are
preferably shorter and wider than those usually employed and are not provided
with magnetising coils. In some cases coils may be altogether omitted from the
field magnet pole pieces. In machines the size and construction of which are
not such as to afford the necessary circuits for induced secondary currents in
the frame itself, coils 2ª are provided. These coils may be joined together in
series as shown, or in some cases each coil may be closed upon itself. Where the
coils 2 are joined together in series, as indicated in Figure 1, it will usually be
advisable to provide a switch 2b for opening and closing the circuit. This switch
may also embody a variable resistance 2°. The pole pieces 2 are preferable
laminated as is usual and cast into the body or frame of the field magnet. The
armature 3 which is shown diagrammatically, is preferably of the usual iron clad
type, that is provided with deep slots or grooves in which the coils are located.
the winding being of the usual direct current generator closed coil type, and
connected at one end to the segments of commutator cylinder 4 on which bear
brushes 5, and at the other end to collecting rings 6 on which bear brushes 7. In
the construction shown, four rings and four brushes are employed, which indicates
that the machine is constructed for the transformation of two phase alternating
currents, although it is to be understood that the machine may be constructed
for the transformation of currents of a different number of phases if desired. If
multiphase currents are applied to the armature winding of the machine above
described at the proper points magnetic fields or poles shifting or rotating about
the axis are produced, the armature winding forming the magnetising coils. If
the armature be rotated in a direction opposite to that of the shifting magnetic
field and at an equal rate of speed, the poles or fields will remain fixed in space,
as in an ordinary. machine with field magnets carrying magnetising coils. If
the brushes be located on the commutator cylinder in positions midway between
the poles they will deliver direct current. In order to keep the magnetising
current small there must be a good magnetic path outside of the armature body.
This is provided in the form illustrated by the cast iron frame having the laminated
pole pieces. Substantially the same result may be secured however by a ring of
laminated plates either fixed or rotating with the core and so arranged as to
provide an air gap between them and the core. If the armature coils are of the
same width as the pitch, the magnetic field due to one phase is pointed, while
the resultant of the two phases is flat-topped, the areas of the two being equal,
but the heights being different. Consequently the total induction per pole is
constant, but the maximum induction varies. By making the coils somewhat
narrower than the pitch, the shape of the field due to one phase is made flat on
top and the resultant of the two is also flat. By this means the shape of the
magnetic field may be made almost constant at all times and the maximum induc-
tion will also be constant. The maximum value of the magnetic field corresponds
to the point where the alternating current is supplied to the winding. The direct
current will also set up a magnetic field which is a maximum at the point where
the direct current brushes are in contact. The direct current brushes, should
commutate the coils at the edge of the field which generates the direct current
electromotive force, and consequently the field due to the magnetising alternating
current should be shifted to a ninety degree position with respect to the field
due to the direct current, in order to give proper commutation. This is actually
the condition in the machine, for the magnetizing alternating current lags.
about ninety degrees behind the alternating current electromotive force by reason

page_text: of the fact that the apparent magnetizing energy is much greater than the
true watts when the machine is running without load.
As the load comes on, the alternating current, which is represented by an
equivalent direct current, is in phase with the electromotive force applied, and
therefore at ninety degrees to the magnetizing current. This useful alternating
current will also set up a field. We have then three magnetic fields set up,
two of which are one hundred and eighty degrees from each other and the
third at ninety degrees from each of the others. The two at one hundred and
eighty degrees are those due respectively to the useful alternating current and
the direct current. These are opposite and aproximately equal in value and
they therefore neutralize each other. The field set up by the useful alternating
current is represented in Figure 3 by the line a that by the direct current by
the line b and that by the magnetizing alternating current by the line c.
As
the direct current and the useful alternating currents are very nearly equal in
magnetizing power and oppose each other, the only field in the machine is that
due to the magnetizing current. This may be much less than would be given
by either of the other two fields, or in other words, the magnetizing current in
a properly designed machine of this type may be made much smaller than the
useful current, and the resultant current may be very little greater than the
useful current.
The losses due to the resistance of the windings are inuch less
than in a direct current generator delivering the same current. The useful
alternating current at times feeds directly into the direct current brushes and at
the worst condition the winding is utilized advantageously. The resultant copper
loss due to the useful alternating current is about 38 per cent. for two phases,
and about 60 per cent. for three phases of the loss in a direct current machine.
To this must be added the loss due to the magnetizing currents which is usually
small.
It has been found that if the keeper or outer ring is in the form of a
cast yoke provided with either cast or laminated poles or projections,
as indicated in the drawing, the armature will run at the proper
speed without any other devices for driving. This is similar to making
the external ring with notches to reduce the local field around the commutated
coils.
As has already been stated in substance, coils located on the pole pieces and
short circuited on themselves are useful and desirable in machines the yokes or
frames of which are laminated or are so small in cross section that they do not
afford proper circuits for induced secondary currents.
A machine like that described is independent of wave form and may, there-
fore, be run in connection with any type of alternating current generator. Such
a machine will run steadily under any condition whereas a rotary transformer
of the ordinary form is sensitive to line drop, adjustment of field strength etc.
Several machines of the type described may be run from a common set of bus
bars, without interfering with the operation of each other in any way.. The
efficiency of such machines is high on account of their being no field losses, and
the amount of copper employed is only about one fourth of that necessary in the
ordinary form of rotary transformer.
In Figure 4 I have shown a system for utilising two phase alternating currents
in connection with a direct current work circuit embodying a neutral or com-
pensating third conductor. This form of work circuit in which the translating
devices are arranged in two sets or series each of which are connected in multiple
between the one of the main conductors and the neutral or compensating conductor
is well known in the art, but heretofore it has been usual to employ two direct
current generators in connection with such a system in order to secure the desired
results..
With this form of my invention I employ a two phase generator 8 with the
two circuits of which are respectively connected the primary windings 9 and 10

page_text: of stationary transformers 11 and 12. The terminals of the secondaries 13 and 14
of these transformers are connected to corresponding collector rings of the rotary
transformer 15. The outer or main conductors 16 and 17 of the direct current
circuit are supplied with current from the commutator 18 of the said rotary
transformer. A third conductor 19 extends between the conductors 16 and 17,
and the translating devices are arranged in two sets or groups, one set or group
being connected between the conductors 16 and 19, and the other set between
the conductors 17 and 19. In case the two sets of translating devices are equal
in number and kind, there will be no unbalancing of the circuit and transfer
of energy, as is well understood. In order to provide however for the transfer
of energy in one direction or the other, according to which side of the circuit is
overloaded with reference to the other, I connect the middle conductor 19 to the
middle point of the winding of each of the secondaries 13 and 14 of the trans-
formers 11 and 12. When the middle conductor is so connected, the potential.
between it and each of the main conductors 16 and 17 is one half that between
the two conductors 16 and 17, and if there is an unbalancing of the loads
energy will be transferred to or from the middle points of the secondaries 13
and 14, as the case may be, in the same manner as in the systems heretofore in
use, in which the balancing conductor is connected between two direct current
generators employed for supplying the work circuit with energy.
If the conductor 19 is connected to the middle points of the secondaries. 13
and 14, the currents which flow in it are always direct currents. Although an
alternating current flows in each of the transformer secondary coils a reversal
takes place at its ends once in each alternation.. The direct current flowing in
conductor 19 is therefore a true alternating current in the transformer coil,.
the coil being reversed with reference to the current rather than the current
with reference to the coil. The coil thus acts as an auto-transformer and not as
a choke coil in supplying equal electromotive force to the two branches of the
direct current circuit.
In Figure 5 I have shown a system in which the two phase alternating current
generator 8 supplies energy to two auto-converters 20 and 21, the leads to the
collecting rings of the rotary transformer 15 being taken from such points in
the single winding of these converters as to reduce the applied electromotive
force the desired amount. In this case as in the one above described, the direct
current is supplied from the commutator 18 of the rotary transformer to the
outer conductors 16 and 17 of the direct current work circuit, and the neutral or
balancing conductor 19 is connected to the middle points of the windings 20
and 21. If the electromotive force supplied by the generator 8 is suitable for
application directly to the rotary transformer, the secondary leads may also be
connected to the terminals of the coils 20 and 21, in which case the transfer of
energy will be effected to and from the middle points of these coils in the same
manner as above described, but there will be no reduction of voltage between
the generator 8 and the rotary transformer 15. In Figure 5 I have also shewn
two additional direct current work circuits 22, 23 and 24, 25, the conductors of
each of which are connected respectively to one of the direct current terminals
of the rotary transformer and to the middle points of the windings of the
stationary transformers 20 and 21. With this arrangement I am enabled to
utilize direct current for any desired purpose, the potential between the con-
ductors 22 and 23 and between the conductors 24 and 25 being one half that
across the brushes of the commutator 18 and equal to that between the con-
ductors 16 and 19 and that between the conductors 17 and 19. Either or both
of these work circuits 22, 23 and 24, 25, may be employed in connection with
the circuits 17 and 19, or by themselves.
In Figures 6 I have shewn the system illustrated in Figure 4, except that a
three phase generator 8° and a three phase transformer 26 are employed in lieu 5
of the two, phase generator and the two phase transformers shewn in Figure 4.
With the arrangement shewn, in which the star winding of transformers is
4

page_text: employed, if the neutral or compensating wire 19 is connected to the middle
point of the secondary, as indicated, the results above described will be secured.
In each of the systems above described, the rotary transformer 15 may be of the
type shewn in Figures 1 and 2, in which only the armature is provided with
magnetizing coils, or the usual form of transformer may be employed, as may
be desired.
་
In Figure 7 I have shewn a single phase generator 8b and a single trans-
former 27, the rotary transformer 15" in this case being supplied with a single
phase current from the secondary of the transformer 27. The latter is provided
with a field magnet winding 28 in order that it may operate without being
driven by external means. The conductors 16, 17 and 19 of the direct current
circuit are arranged to operate in the same manner as the corresponding con-
ductors in the systems before described.
The direct current circuits thus far described are suitable for both light and
power purposes. In order to secure a uniform and equal potential between
the conductors 16 and 19 and 17 and 19, and the transmission to and from the
stationary transformer secondary of direct currents, it is necessary that the neutral
conductor be connected to the middle point of such secondary as has been above
described. If, however, it is desired to secure in connection with either or both
of the conductors 16 and 17 an electromotive force suitable for the operation
of lights, it may be done by means of a conductor 29 which is connected to any
point in the secondary of the stationary transformer. I have shewn the secondary
of the transformer 27 as provided with loops leading to contact points 30, with
the latter of which a movable switch arm 31 engages. With the switch arm 31
in the position shewn, the potential between the conductor 17 and 29 will be
substantially seven-tenths of that between the conductor 16 and 17, but the
current transmitted will be alternating or fluctuating, and therefore not suitable
for other purposes than for electric lighting. By moving the switch arm 31,
so as to connect the conductor 29 with other points in the secondary of the trans-
former 27, other voltages between seven-tenths and one half of the voltage across
the terminals of the rotary transformer may be secured."
In Figure 7 I have also shewn a direct current motor 32 supplied with energy
from the circuit 16, 17, and provided with a shunt field winding 33. As the
electromotive force supplied to the motor 32 from the circuit 16, 17, is constant.
the motor will run at a given constant speed when so connected.
In order to
run the motor at double this normal speed, I reduce the counter electromotive
force one-half as follows: I provide the motor with a pair of collecting rings 34
and connect these rings by an auto-transformer 35. I also connect the middle
point of the transformer 35 with the branch conductor 17° leading from con-
ductor 17 by means of a conductor 36 and a switch arm 38. The switch arm 38
is so arranged as to permit of connecting the said branch conductor 17ª with either
the conductor 36 or with the corresponding brush of the commutator 37.
I desire it to be understood that the details of my invention may be varied
from what is shewn and described without departing from its spirit and
scope.
1
COMPLETE SPECIFICATION.
Improvements in Methods of and Means for Electrical Conversion
and Distribution.
I, BENJAMIN GARVER LAMME, c/o., Westinghouse Electric and Manufacturing
Company, East Pittsburg, State of Pennsylvania, United States of America,

page_text: Electrical Engineer, 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:―
My invention relates to systems of electric distribution involving means for
converting alternating into direct currents and it has for one of its objects to
provide a rotary transformer for converting multiphase alternating currents
into direct currents, which shall operate efficiently and satisfactorily irrespective
of the wave form of the currents supplied to it and the number and character
of the machines which may be coupled in parallel with it.
A further object of the invention is to provide a method and a means whereby
a three-wire direct current system may be supplied with energy from an alternat-
ing current supply circuit at a minimum expense and loss of energy and with
a maximum degree of efficiency.
A further object of the invention is to provide a method and means whereby
direct current motors may be run at different speeds without varying the field
magnet excitation or the applied electro-motive force.
A further object of the invention is to provide means whereby a plurality of
different voltages may be secured in connection with an alternating current cir-
cuit and a rotary transformer.
Reference being had to the accompanying drawings,
Figure 1 is an end elevation of a rotary transformer constructed in accordance
with one feature of my invention, the end bearing being broken away and the
armature conductors and commutator being shown diagrammatically.
Figure 2 is a side elevation of the rotary transformer shewn in Figure 1.
Figure 3 is a diagram illustrating the phase relation and amplitude of the
magnetic fields produced by the armature currents of the transformer shewn in
Figures 1 and 2.
Figure 3 is a development shewing the armature winding.
Reference being had to Sheet of the drawings left with my Provisional Specifi-
cation,
Figure 4 is a diagram illustrating another feature of my invention in con-
nection with a two-phase alternating current system of distribution.
Figure 5 is a similar view shewing a different form of stationary transformer
and additional direct current circuits.
Figure 6 is a diagram illustrating the invention in connection with a three
phase alternating current system.
Figure 7 is a diagram illustrating two additional features of my invention in
connection with a single phase alternating current system.
Reference being now had particularly to Figures 1, 2, 3 and 3ª, 1 is a multi-
polar field magnet of ordinary construction, except that the pole pieces 2 are
preferably shorter and wider than those usually employed and are not provided
with magnetising coils. In some cases coils may be altogether omitted from the
field magnet pole pieces. In machines the size and construction of which are
not such as to afford the necessary circuits for induced secondary currents in
the frame itself, coils 2ª are provided. These coils may be joined together in
series as shown, or in some cases each coil may be closed upon itself. Where the
coils are joined together in series, as indicated in Figure 1, it will usually be
advisable to provide a switch 2b for opening and closing the circuit. This switch
may also embody a variable resistance 2. The pole pieces 2 are preferably
laminated as is usual and cast into the body or frame of the field magnet. The
armature 3 which is shewn diagrammatically, and a development of which is
illustrated in Figure 3 is preferably of the usual iron clad type,
that is provided with deep slots or grooves in which the coils are located,
the winding being of the usual direct current generator closed coil type, and
connected at one end to the segments of commutator cylinder 4 on which bear
brushes 5, and at the other end to collecting rings on which bear brushes 7. In
the construction shewn, four rings and four brushes are employed, which indicates

page_text: that the machine is constructed for the transformation of two phase alternating
currents, although it is to be understood that the machine may be constructedl
for the transformation of currents of a different number of phases if desired. If
multiphase currents are applied to the armature winding of the machine above
described at the proper points magnetic fields or poles shifting or rotating about
the axis are produced, the armature winding forming the magnetising coils. If
the armature be rotated in a direction opposite to that of the shifting magnetic
field and at an equal rate of speed, the poles or fields will remain fixed in space.
as in an ordinary machine with field magnets carrying magnetising coils. If
the brushes be located on the commutator cylinder in positions midway between
the poles they will deliver, direct current. In order to keep the mhgnetising
current small there must be a good magnetic path outside of the armature body.
This is provided in the form illustrated by the cast iron frame having the laminated
pole pieces. Substantially the same result may be secured however by a ring of
laminated plates either fixed or rotating with the core and so arranged as to
provide an air gap between them and the core. If the armature coils are of the
same width as the pitch, the magnetic field due to one phase is pointed, while
the resultant of the two phases is flat-topped, the areas of the two being equal,
but the heights being different. Consequently the total induction per pole is
constant, but the maximum induction varies over the polar surface. In the
present invention the coils are made narrower than the pitch, as will be seen
by examining Figure 3 and the shape of the field due to one phase is
thereby made flat on top, or the maximum induction occurs over a greater
portion of the polar surface at the same instant, the resultant of the two
phases is also flat as will be obvious. By this means the shape of the
magnetic field may be made almost constant at all times and the maximum induc-
tion will also be constant. The maximum value of the magnetic field corresponds
to the point where the alternating current is supplied to the winding. The direct
current will also set up a magnetic field which is a maximum at the point where
the direct current brushes are in contact. The direct current brushes should
commutate the coils at the edge of the field which generates the direct current
electromotive force, and consequently the field due to the magnetizing alternating
current should be shifted to a ninety degree position with respect to the field
due to the direct current, in order to give proper commutation. This is actually.
the condition in the machine, for the magnetizing alternating current lags
about ninety degrees behind the alternating current electromotive force by reason
of the fact that the apparent magnetizing energy is much greater than the
true watts when the machine is running without load.
As the load comes on, the alternating current, which is represented by an .
equivalent direct current (namely, that given out on the direct current side of
the transformer) is in phase with the electromotive force applied, and therefore
at ninety degrees to the magnetizing current. This which may be called the use-
ful alternating current will also set up a field. We have then three magnetic fields
set up, two of which are one hundred and eighty degrees from each other and the
third at ninety degrees from each of the others. The two at one hundred and
eighty degrees are those due respectively to the useful alternating current and
the direct current These are opposite and aproximately equal in value and
they therefore neutralize each other. The field set up by the useful alternating
current is represented in Figure 3 by the line a that by the direct current by
the line band that by the magnetizing alternating current by the line c. As
the direct current and the useful alternating currents are very nearly equal in
magnetizing power and oppose each other, the only field in the machine is that
due to the magnetizing current. This may be much less than would be given
by either of the other two fields, or in other words, the magnetizing current in
a properly designed machine of this type may be made much smaller than the
useful current, and the resultant current may be very little greater than the
useful current,

page_text: The losses due to the resistance of the windings are much less than in a direct
current generator delivering the same current, and if in place of connecting the
slip rings 6 to that end of the armature opposite the commutator as shewn for
the sake of clearness in Figure 3" they are connected to the windings at the same
end às the commutator or to the commutator bars themselves, the useful alternat-
ing current will at times feed directly into the direct current brushes.
resultant copper loss due to the useful alternating current is about 36 per cent.
for two phases, and about 60 per cent. for three phases of the loss in a direct
current machine. To this must be added the loss due to the magnetizing current
which is usually very small.
The
It has been found that if the keeper or outer ring is in the form of a
cast yoke provided with either cast or laminated poles or projections,
18 indicated in the drawing, the armature will run at the proper
speed without any other devices for driving. This is similar to making
the external ring with notches to reduce the local field around the commutated
coils.
As has already been stated in substance, coils located on the pole pieces and
shortcircuited on themselves are useful and desirable in machines the yokes or
frames of which are laminated or are so small in cross section that they do not
afford proper circuits for induced secondary currents.
A machine like that described is independent of wave form and may, there-
fore, be run in connection with any type of alternating current generator. Such
a machine will run steadily under any condition whereas a rotary transformer
of the ordinary form is sensitive to line drop, adjustment of field strength etc.
Several machines of the type described may be run from a common set of bus
bars, without interfering with the operation of each other in any way. The
efficiency of such machines is high on account of there being no field losses, and
the amount of copper employed is only about one fourth of that necessary in the
ordinary form of rotary transformer.
Referring now to sheet of the drawings left with my provisional specification,
in Figure 4 I have shown a system for utilising two phase alternating currents
in connection with a direct current work circuit embodying a neutral or com-
pensating third conductor. This form of work circuit in which the translating
devices are arranged in,two sets or series each of which are connected in multiple
between one of the main conductors and the neutral or compensating conductor
is well known in the art, but heretofore it has been usual to employ two direct
current generators in connection with such a system in order to secure the desired
results.
With this form of my invention I employ a two phase generator 8 with the
two circuits of which are respectively connected the primary windings 9 and 10
of stationary transformers 11 and 12. The terminals of the secondaries 13 and 14
of these transformers are connected to corresponding collector rings of the rotary
transformer 15. The outer or main conductors 16 and 17 of the direct current
circuits are supplied with current from the commutator 18 of the said rotary
transformer. A third conductor 19 extends between the conductors 16 and 17,
and the translating devices are arranged in two sets or groups, one set or group
being connected between the conductors 16 and 19, and the other set between
the conductors 17 and 19. In case the two sets of translating devices are equal
in number and kind, there will be no unbalancing of the circuit and transfer
of energy, as is well understood. In order to provide however for the transfer
of energy in one direction or the other, according to which side of the circuit is
overloaded with reference to the other, I connect the middle conductor 19 to the
middle point of the winding of each of the secondaries 13 and 14 of the trans-
formers 11 and 12. When the middle conductor is so connected, the potential
between it and each of the main conductors 16 and 17 is one half that between
the two conductors 16 and 17, and if there is an unbalancing of the loads

page_text: energy will be transferred to or from the middle points of the secondaries 13
and 14, as the case may be, in the same manner as in the systems heretofore in
use, in which the balancing conductor is connected between two direct current
generators employed for supplying the work circuit with energy.
If the conductor 19 is connected to the middle points of the secondaries 13
and 14, the currents which flow in it are always direct currents. Although an
alternating current flows in each of the transformer secondary coils a reversal
takes place at its ends once in each alternation. The direct current flowing in
conductor 19 is therefore a true alternating current in the transformer coil,
the coil being reversed with reference to the current rather than the current
with reference to the coil. The coil thus acts as an auto-transformer and not as
a choke coil in supplying equal electromotive force to the two branches of the
direct current circuit.
In Figure 5 I have shown a system in which the two phase alternating current
generator 8 supplies energy to two auto-converters 20 and 21, the leads to the
collecting rings of the rotary transformer 15 being taken from such points in
the single winding of these converters as to reduce the applied electromotive
force the desired amount. In this case, as in the one above described, the direct
current is supplied from the commutator 18 of the rotary transformer to the
outer conductors 16 and 17 of the direct current work circuit, and the neutral or
balancing conductor 19 is connected to the middle points of the windings 20
and 21. If the electromotive force supplied by the generator 8 is suitable for
application directly to the rotary transformer, the secondary leads may also be
connected to the terminals of the coils 20 and 21, in which case the transfer of
energy will be effected to and from the middle-points-of-these-coils-in the same
manner as above described, but there will be no reduction of voltage between
the generator 8 and the rotary transformer 15. In Figure 5 I have also shown
two additional direct current work circuits 22, 23 and 24, 25, the conductors of
each of which are connected respectively to one of the direct current terminals
of the rotary transformer and to the middle points of the windings of the
stationary transformers 20 and 21. With this arrangement I am enabled to
utilize direct current for any desired purpose, the potential between the con-
ductors 22 and 23 and between the conductors 24 and 25 being one hair that
across the brushes of the commutator 18. and equal to that between the con-
ductors 16 and 19 and that between the conductors 17 and 19. Either or both
of these work circuits 22, 23 and 24, 25, may be employed in connection with
the circuits 17 and 19, or by themselves.
In Figure. 6 I have shewn the system illustrated in Figure 4, except that a
three phase generator 8 and a three phase transformer 26 are employed in lieu
of the two phase generator and the two phase transformers shown in Figure 5.
With the arrangement shewn, in which the star winding of transformers is
employed, if the neutral or compensating wire 19 is connected to the middle
point of the secondary, as indicated, the results above described will be secured.
In each of the systems above described, the rotary transformer 15 may be of the
type shewn in Figures 1 and 2, in which only the armature is provided with
magnetizing coils, or the usual form of transformer may be employed, as may
be desired.
In Figure 7 I have shewn a single phase generator 8b and a single trans-
former 27, the rotary transformer 15 in this case being supplied with a single
phase current from the secondary of the transformer 27. The latter is provided
with a field magnet winding 28, in order that it may operate without being
driven by external means. The conductors 16, 17 and 19 of the direct current
circuit are arranged to operate in the same manner as the corresponding con-
ductors in the systems before described.
The direct current circuits thus far described are suitable for both light and
power purposes. In order to secure a uniform and equal potential between
11

page_text: the conductors 16 and 19 and 17 and 19, and the transmission to and from the
stationary transformer secondary of direct currents, it is necessary that the neutral
conductor be connected to the middle point of such secondary as has been above
described. If, however, it is desired to secure in connection with either or both
of the conductors 16 and 17 an electromotive force suitable for the operation
of lights, it may be done by means of a conductor 29 which is connected to any
point in the secondary of the stationary transformer. I have shewn the secondary
of the transformer 27 as provided with loops leading to contact points 30, with
the latter of which a movable switch arm 31 engages. With the switch arm 31
in the position shewn, the potential between the conductor 17 and 29 will be
substantially seven-tenths of that between the conductor 16 and 17, but the
current transmitted will be alternating or fluctuating, and therefore not suitable
for other purposes than for electric lighting. By moving the switch arm. 31,
so as to connect the conductor 29 with other points in the secondary of the trans-
former 27, other voltages between seven-tenths and one half of the voltage across
the terminals of the rotary transformer may be secured.
In Figure 7 I have also shewn a direct current motor 32 supplied with energy
from the circuit 16, 17, and provided with a shunt field winding 33. As the
electromotive force supplied to the motor 32 from the circuit 16, 17, is constant,
the motor will run at a given constant speed when so connected. In order to
run the motor at double this normal speed, I reduce the counter electromotive
force one-half as follows; I provide the motor with a pair of collecting rings 34
connected to the armature winding in the usual manner and connect theso
rings by an auto-transformer or resistance 35. I also connect the middle
point of the transformer 35 with the branch conductor 17 leading from the con-
ductor 17 by means of a conductor 36 and a switch arm 38. The switch arm 38
is so arranged as to permit of connecting the said branch conductor 17 with either
the conductor 36 or with the corresponding brush of the commutator 37. Now tho
difference of potentials between the middle point of the transformer 35 and
the commutator brush is half that which normally exists between the commutator
brushes hence when the switch 38 is turned to the position shewn in the drawing
the counter electromotive force has been reduced to half what it was before con-
sequently the motor will rotate at double the speed.
I desire it to be understood that the details of my invention may be varied
from what is shewn and described without departing from its spirit and
scope.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is:-
1. For polyphase currents, a rotary transformer having a rotary or stationary
multipolar field. magnet either without magnetizing coils or provided with coils
each wound in a closed circuit or forming part of a closed circuit, and a rotary
armature wound with coils to which the polyphase current mains are connected
substantially as described.
2. For polyphase currents, a rotary transformer having a rotary or stationary
multipolar field magnet, and a rotary armature wound with coils the width of
each coil being considerably less than the distance between the centres of the
field magnet poles for the purpose specified.
3. A rotary transformer constructed substantially as described with reference
to Figures 1 to 3 of the accompanying drawings.
4. A system of distribution in which translating devices arranged on a three
wire or similar system are fed from the direct current side of a rotary transformer
supplied with energy from a stationary transformer or auto-transformer to a point
intermediate of the terminals of which the neutral wire of the three wire of
like system is joined.

page_text: 5. The various systems of distribution described with reference to Figures 5 to 8
of the accompanying drawings.
6. The system of operating an electric motor at different speeds by reducing
its counter-electromotive force substantially as described.
Dated the Twenty-fourth day of June 1898...
W. P. THOMPSON & Co.,
322, High Holborn, London, W.C., Patent Agents for the Applicant.