Improvement in Systems of Electrical Distribution and kegulation.
Year: 1899

page_text: Improvement in Systems of Electrical Distribution and kegulation.
I, BENJAMIN GARVER LAMME, of 230, Stratford Avenue, Pittsburgh, in the
County of Allegheny, and State of Pennsylvania, U.S.A., Electrical Engineer, do
hereby declare the nature of this invention to be as follows:-
My invention relates to a system of electrical distribution and regulation, and
in particular to those systems wherein rotary transformers are employed for trans-
forming direct currents into alternating currents of one or more phases.
The object of my invention is to regulate or govern the speed of the armature
of the rotary transformer, irrespective of variation in the inductive load in the
alternating current circuit.
I attain the above ends by providing an auxiliary circuit including choking coils
so proportioned as to compensate for changes in the inductive load and thereby
maintain constant or regulate the armature reaction.
It has been determined that if the current and electromotive force waves sup-
plied by an alternating current generator are in step, the armature reaction will
be substantially zero, hence, the field-magnet strength will not be altered; if,
however, the current wave lags, the armature reaction will be increased, and the
field-magnet strength correspondingly diminished. If, on the other hand, the
current wave leads or is in advance of the electromotive force wave, the armature
reaction will be such as to strengthen the field-magnet. It is clear, therefore,
that the field-magnet strength depends on the armature reaction, hence, the
speed of the transformer can be governed by varying the relationship of current
to electromotive force.
In the accompanying drawings:-
-
Fig. 1 is a diagram of a system of distribution in which a rotary transformer
is used to transform direct currents into alternating currents, the alternating
current circuit being provided with auxiliary circuits containing choke coils of
variable self-induction.
Fig. 2 is a diagram illustrating current and magnetic saturation values per-
taining to the regulating choke coils indicated in Fig. 1, for different rates of
alternations and a constant electromotive force.
Referring now to Fig. 1, 1 is a direct current generator provided with

page_text: mains 3 and 4 which supply through a commutator 5 the armature 6 of a rotary
transformer. The field-magnet coils are indicated at 7 as being connected as
a shunt to the armature and this type of winding is preferred. A compound
field-magnet winding may, however, be used if desired. The transformer sup-
plies two-phase currents to the circuits 8, 9, 10, and 11, through collector
rings 2. Said circuits are shewn as severally supplying single-phase trans-
lating devices 12 and also an induction motor 13. Connected across the circuits 8,
9, and 10, 11, respectively, are choke coils 14, 15, each of which is provided
with an adjustable core 16, 17, respectively, and with a series of leads to which
are connected switches 18, and 19, for varying the active length of the choke coil
or cutting it out of circuit altogether. It will be clear that the self-induction of
the choke coils may be varied by adjusting the movable cores 16, 17, or varying
the active length of the coils, or by the use of both these means in combination.
It is clear from what has already been said that variation in such inductive resis-
tance will vary the speed of the armature 6 of the rotary transformer and thereby
vary the rate of alternations in the alternating current supplied from said
armature and the speed of the induction motor 13, and if a mere variation in
speed of this latter motor is required, the choke coils 14 and 15 may be adjusted
by hand.
If, however, it is desired to maintain constant the speed of the armature 6 of
the rotary transformer, notwithstanding variation in the inductive load, no mani-
pulation of the choke coils will be required after such coils have once been
adjusted to suit the system of which they form part. If we assume that the
choke coils 14 and 15 are adjusted to produce a definite current lag in each of
the circuits 8, 9 and 10, 11, respectively, there being either no load on these
circuits or a non-inductive load thereon, such for example, as the lamps 12, the
speed at which the armature 6 will rotate will depend upon the armature reaction
produced by the lagging current.
If, now, an inductive load such as the motor 13 be added to the work circuit an
additional lag in the current will be produced, consequently, the speed of the
rotary transformer will tend to increase. As the speed increases the rate of
alternations will also increase, and the choke coils 14, 15, will there-
fore take less current than before, and consequently will have less
reactive effect upon the circuit and the rotary transformer. If the choke coils
are properly designed and adjusted the decrease in the current taken by them at
the increased rate of alternations will compensate for the reactive effect due
to the increase in the inductive load on the work circuit, and the speed of the
transformer will consequently drop to substantially the same as it was before such
inductive load was put on.
The action of the choke coils under different rates of alternations is illustrated
in Fig. 2 in which the current is measured horizontally from the point a and
the electromotive force is measured vertically. Assuming that for a given rate
of alternations, the electromotive force is represented by the line c-b, and the
current taken by the choke coils is represented by the line ac, then the satura-
tion curve will be ab. If the rate of alternations increases, the electromotive 4
force remaining constant, so that the degree of saturation is represented by the
curve a-d, then the current taken by the coils will fall to the value repre-
sented by the line a―e. If the rate of alternations increases without changes
in the electromotive force so that the degree of saturation is represented by the
curve a-f, the current will fall to the value represented by line a—y.
With the apparatus indicated it will probably not be possible to secure abso-
lutely uniform speed of the rotary transformer under variations in load, but a
sufficiently close regulation for practical purposes may be obtained, at the same
time the apparatus is exceedingly simple and inexpensive.
Although I have shewn two-phase alternating current circuits joined to the 5
armature 6, it will be obvious that the invention is not restricted in this respect,
as circuits of any desired number of phases may be utilized.

page_text: Furthermore I do not restrict myself to any specific construction of rotary
transformer, either as regards the armature or field-magnet of the machine.
Dated the 28th day of March 1898.
Improvement in Systems of Electrical Distribution and Regulation.
I, BENJAMIN GARVER LAMME, of 230, Stratford Avenue, Pittsburgh, in the
County of Allegheny, and State of Pennsylvania, U.S.A., 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 electrical distribution and regulation, and
in particular to those systems wherein rotary transformers are employed for trans-
forming direct currents into alternating currents of one or more phases.
The object of my invention is to regulate or govern the speed of the armature
of the rotary transformer, irrespective of variation in the inductive load in the
alternating current circuit.
I attain the above ends by providing an auxiliary circuit including choking coils
so proportioned as to compensate for changes in the inductive load and thereby
maintain constant or regulate the armature reaction.
It has been determined that if the current and electromotive force waves sup-
plied by an alternating current generator are in step, the armature reaction will
be substantially zero, hence, the field-magnet strength will not be altered; if,
however, the current wave lags, the armature reaction will be increased, and the
field-magnet strength correspondingly diminished. If, on the other hand, the
current wave leads or is in advance of the electromotive force wave, the armature
reaction will be such as to strengthen the field-magnet. It is clear, therefore,
that the field-magnet strength depends on the armature reaction, hence, the
speed of the transformer can be governed by varying the relationship of current
to electromotive force.
In the drawings accompanying my Provisional Specification:-
-
Figure 1 is a diagram of a system of distribution in which a rotary transformer
is used to transform direct currents into alternating currents, the alternating
current circuit being provided with auxiliary circuits containing choke coils of
variable self-induction.
Figure 2 is a diagram illustrating current and magnetic saturation values per-
taining to the regulating choke coils indicated in Fig. 1, for different rates of
alternations and a constant electromotive force.
Referring now to Figure 1, 1 is a direct current generator provided with
mains 3 and 4 which supply through a commutator 5 the armature 6 of a rotary
transformer. The field-magnet coils are indicated at 7 as being connected as
a shunt to the armature and this type of winding is preferred. A compound
field-magnet winding may, however, be used if desired. The transformer sup-
plies two-phase currents to the circuits 8, 9, 10, and 11, through collector
rings 2. Said circuits are shewn as severally supplying single-phase trans-
lating devices 12 and also an induction motor 13. Connected across the circuits 8,
9, and 10, 11, respectively, are choke coils 14, 15, each of which is provided
with an adjustable core 16. 17 respectively, and with a series of leads to which

page_text: are connected switches 18 and 19 for varying the active length of the choke coil
or cutting it out of circuit altogether. It will be clear that the self-induction of
the choke coils may be varied by adjusting the movable cores 16, 17 or varying
the active length of the coils, or by the use of both these means in combination.
It is clear from what has already been said that variation in such inductive resis-
tance will vary the speed of the armature 6 of the rotary transformer and thereby
vary the rate of alternations in the alternating current supplied from said
armature and the speed of the induction motor 13, and if a mere variation in
speed of this latter motor is required, the choke coils 14 and 15 may be adjusted
by hand.
If, however, it is desired to maintain constant the speed of the armature 6 of
the rotary transformer, notwithstanding variation in the inductive load, no mani-
pulation of the choke coils will be required after such coils have once been
adjusted to suit the system of which they form part. If we assume that the
choke coils 14 and 15 are adjusted to produce a definite current lag in each of
the circuits 8, 9 and 10, 11, respectively, there being either no load on these
circuits or a non-inductive load thereon, such for example, as the lamps 12, the
speed at which the armature 6 will rotate will depend upon the armature reaction
produced by the lagging current.
If, now, an inductive load such as the motor 13 be added to the work circuit an
additional lag in the current will be produced, consequently, the speed of the
rotary transformer will tend to increase. As the speed increases the rate of
alternations will also increase, and the choke coils 14, 15, will there-
fore take less current than before, and consequently will have less
reactive effect upon the circuit and the rotary transformer. If the choke coils
are properly designed and adjusted the decrease in the current taken by them at
the increased rate of alternations will compensate for the reactive effect due
to the increase in the inductive load on the work circuit, and the speed of the
transformer will consequently drop to substantially the same as it was before such
inductive load was put on.
The action of the choke coils under different rates of alternations is illustrated
in Figure 2 in which the current is measured horizontally from the point a and
the electromotive force is measured vertically. Assuming that for a given rate
of alternations the electromotive force is represented by the line b, and the
current taken by the choke coils is represented by the line ac, then the satura-
tion curve will be a-b. If the rate of alternations increases, the electromotive
force remaining constant, so that the degree of saturation is represented by the
curve a-d, then the current taken by the coils will fall to the value repre-
sented by the line a-c. If the rate of alternations increases without changes
in the electromotive force so that the degree of saturation is represented by the
curve a-f, the current will fall to the value represented by line a-g.
With the apparatus indicated it will probably not be possible to secure abso-
lutely uniform speed of the rotary transformer under variations in load, but a
sufficiently close regulation for practical purposes may be obtained, at the same
time the apparatus is exceedingly simple and inexpensive.
Although I have shewn two-phase alternating current circuits joined to the
armature 6, it will be obvious that the invention is not restricted in this respect,
as circuits of any desired number of phases may be utilized.
Furthermore I do not restrict myself to any specific construction of rotary
transformer, either as regards the armature or field-magnet of the machine.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what
I claim is:
1. For automatically maintaining substantially constant the speed of a rotary
transformer feeding an alternating current circuit having a variable inductive
load, a choking coil connected in parallel with the variable inductive load and se

page_text: adjusted that it will compensate for the variation in the armature reaction of the
rotary transformer produced by the variation in the inductive load.
2. A system of electrical distribution in which a rotary transformer is used to
transform direct currents into alternating currents with a choke coil or coils for
regulating or governing the speed of the rotary transformer substantially as
described.
Dated 22nd day of December 1899.
W. P. THOMPSON & Co.,
Of London, Liverpool, Manchester and Birmingham.