Improvements in or relating to Alternating Current Systems of Distribution and Regulation.
Year: 1896

page_text: Date of Application, 24th Nov., 1896
1002
Oth Out
1007
PROVIDIONAL OF ECIFICATION.
[Communicated from abroad by BENJAMIN G. LAMME and RALPH D. MERSHON,
both of Pittsburgh, County of Allegheny, State of Pennsylvania, United
States of America.]
Improvements in or relating to Alternating Current Systems of
Distribution and Regulation.
I, REGINALD BELFIELD, of 32, Victoria Street, in the City of Westminster,
Electrician, do hereby declare the nature of this invention to be as follows:-
The invention relates to alternating current systems of distribution and regula-
tion, and it has for its object to provide a means whereby the effect of self-induction
in alternating current transmission circuits may be neutralized and whereby the
alternating current generator supplying the circuit may be so regulated that it
may supply a maximum amount of real energy to the circuit; a further object of
the invention is to provide a means for and method of automatic regulation in the
systems of electrical distribution in which rotary transformers are employed for
transforming electric alternating currents into direct currents for use in operating
translating devices, whereby the electromotive force delivered to the direct current
circuit will be automatically adjusted in accordance with changes in the load upon
such circuit, so as to give an approximately constant electromotive force or an
increasing electromotive force either at the terminals of the machine or at the load
end of the circuit.
It is well known that all alternating current circuits have more or less self-
induction, the amount depending upon the length of the circuit and the number
and character of the translating devices supplied by it. In cases where the work
circuit mains are located at a considerable distance from the generator, and trans-
formers are employed either for reducing the voltage at the work circuit end of
the feeders, or for both raising the voltage at the generator end and reducing it at
the work cirouit end, the amount of self-induction is sufficient to introduce a
considerable lag factor which will materially reduce the amount of real energy
available for use in the work circuit. The current lag in the circuit also affects
the operation and output of the generator, since it increases the armature reaction
which, in turn, weakens the field magnet.
The present invention provides a means whereby a rotary transformer may be
utilized for the transformation of alternating currents into direct currents and at
the same time serve to bring the alternating current into step with the electro-
motive force in the circuit, and to so regulate the generator that it will give a
maximum output of real energy.
As the voltage at the direct current end of a rotary transformer always bears a
definite fixed relation to that at the alternating current end, it is necessary to pro-
vide some means for raising the voltage supplied to the latter, with the increase
of load upon the direct current circuit, in order to compound or over-compound
the transformer, and thus secure an approximately constant, or increasing, electro-

page_text: motive force, either at its direct terminals or at the load ond of its circuit under
varying loads.
In carrying out the invention a transformer is employed the armature of which
may have either one or a plurality of windings as inay he desired, and the field
magnet of which is provided with both shunt and series coils. In the alternating
current supplying the transformer we introduce inductive resistance, the amount
of which will depend upon the degree of compounding or over-compounding which
is desired. By properly proportioning the resistance of the shunt circuit, the field
charge for the condition of no load may be made such that the current supplied to
the transformer will be either leading, lagging, or in step with the electromotive
force. For the purpose of the invention, however, the field charge will preferably
be so adjusted that there will be a lagging current through the armature coils at
no load. As the load comes on, the series coil will strengthen the field of the
machine, and thus reduce the lagging component and consequently the drop of
voltage in the alternative current circuit due to the inductive resistance,
until finally all of the current supplied to the transformer will be in step with the
electromotive force at its terminals. When this condition is attained there will
still be some drop in electromotive force between the source of current and the
terminals of the rotary transformer, but if the field of the transformer continues
to strengthen by reason of the increase of current through its series coils, there
will be added to the current flowing through the transformer a component in
advance of the electromotive force at the transformer terminals, and this will still
further decrease the drop in voltage due to the inductive resistance included in the
circuit between the source of ourrent and the transformer, until the electromotive
force supplied to the transformer is approximately equal to that of the source of
the current.
If the load is increased beyond this point, the electromotive force supplied to the
transformer may remain approximately equal to that of the source of current, or
may fall below or rise above it, according to the relative adjustment of the
inductive resistance and the transformer field magnet coils.
In some cases, however, it is preferable in obtaining this regulating action for
constant or increasing electromotive force at the direct current terminals through-
out the range of load to have such an adjustment of the inductive resistances that
the series coils will at full load cause the electromotive force at the terminals of
the transformer to be about equal to that of the source. Such equality may,
however, by proper adjustment, he made to come at any point between zero and
full load.
In the accompanying drawings
Figure 1 is a diagram of circuits and machines so arranged that the injurious
effects of self-induction in the generating circuit are neutralized.
Figure 2 is another diagram of a system of distribution in which the electro-
motive force supplied to the direct current is automatically adjusted according to
the load on the circuit.
Referring to Figure 1, 1 is a two phase alternating current generator the
armature of which is provided with an inter-connected winding 2. 3 is the field
magnet winding excited by current from a suitable exciter 4. The armature
winding is tapped at four points, and two circuits for each phase are connected
to the winding, as indicated. Step up transformers 5 and 6 are supplied with
currents of one phase, and step up transformers 7 and 8, with currents of a phase
differing 90° therefrom. The secondary of the transformer 5 is connected with a
transmission circuit 9, 10, the secondary of the transformer 6 with a similar
circuit 11, 12, the secondary of the transformer 7 with the circuit 13 and 14, and
the secondary of transformer 8 with the circuit 15. 16. 17 is a step down trans-
former the primary of which is connected with the circuit 9, 10, and 18, 19,
and 20 are similar transformers respectively connected with the several trans-
mission circuits 11-12, 13. 14, and 15 -16. The secondaries of the
transformers 17 and 19 supply current to the alternating current end 21 of a rotary

page_text: transformer 22, and the secondaries of transformers 18 and 20 are similarly
connected to the alternating current end 23 of a rotary transformer 24. The field
magnets of these rotary transformers 22 and 24 are respectively provided with
shunt coils 25 and 26 and series coils 27 and 28. The current from the direct
current ends 20 and 30, respectively, of the rotary transformers 22 and 24, is
supplied to the mains 30* in the usual manner. The armature construction of
the rotary transformers is not illustrated, it being understood that it may be of
any suitable character known in the art and provided with either a single winding
or a plurality of windings.
In a system of apparatus and circuits like that shewn and described the usual
effect of the compound winding for the field magnets of the rotary transformers
obviously depends upon the presence in the alternating current circuits of more or
less self-induction; in fact the unavoidable presence of self-induction in such
circuits is recognized, and it is the object of the present invention to provide a
means whereby the injurious effects of such self-induction may be obviated. If
the field magnet windings of the transformers are properly proportioned and
adjusted the circuit through the series coils will increase as the load upon the
circuit 30 increases, thus strengthening the field and accelerating the phase of
the lagging currents in the alternating current circuits supplying the transformers
until the currents and corresponding electromotive forces are brought substantially.
into step, thus supplying the maximum amount of real energy to the transformers
and reacting upon the generator 1, so as to bring its current and electromotive
force waves into step with each other, and thus reduce the armature reaction
sufficiently to give a materially increased output over what would be secured if
the self-induction of the alternating current circuit were permitted to have its
usual effect upon the current flowing through the circuit.
Referring now to Figure 2, 31 is a rotary transformer the armature of which
may have one or two windings as may be desired. 32 represents the shunt field
magnet winding and 33 the series field magnet winding, and 34 and 30 direct
current feeders supplying mains 38 and 39. Translating devices receiving
currents from said mains are shewn at 40, 41 and 42. Any other desired arrange-
ment of translating devices and cirouits may obviously he employed. 43 and 44
are stationary step-down transformers or converters the primaries of which are
respectively connected with the circuits 45 and 46, and 47 and 48, supplied with
current from a two phase generator 49. It will be understood that in cases where
the generator potential is not too high, the rotary transformer may be supplied
directly therefrom without the interposition of step-down converters. In each alter-
nating current circuit supplied by the secondaries of the converters 43 and 44,
or by the generator directly as the case may be, is a choke coil 50. These coils
may, if desired, however, he included in the circuit supplying the primaries of the
converters 43 and 44, and in some cases such converters may themselves include
sufficient inductive resistance to provide the necessary difference of potential
between the generator and the transformer. The transformer field magnet
windings and the inductive resistance represented by the choke coils 50 will be
adjusted for each particular organization of apparatus; but when once adjusted
for any special case they have a constant value."
I have illustrated the invention as applied to a two phase system of distribution
but it will be understood that it is equally applicable to single phase systems or to
those having a greater number of phases than two. Where choke coils are
employed, as will usually be necessary in order to secure the desired inductive
potential drop, they will be so proportioned that there will be no saturation of their
cores under any condition. As the inductive drop due to the choke coils is
diminished by the strengthening the field under an increase of load and the current
is brought more nearly into step with the electromotive force impressed upon the
circuit by the generator 19 the effective electromotive force supplied by the rotary
transformer to the direct current circuit will be kept up to the desired value. The
inductive resistance and the field coils of the transformer may be made so that the

page_text: current and electromotive force will be brought into step under any desired
conditions of load depending upon the conditions of the plant in connection with
which the invention is employed and the results sought to be secured thereby.
Dated this 24th day of November 1896.
W. P. THOMPSON & Co.,
322, High Holborn, London, W.C., Patent Agents for the Applicant.
Improvements in or relating to Alternating Current Systems of
Distribution and Regulation.
I, REGINALD BELFIELD, of 32, Victoria Street, in the City of Westminster,
Electrician, 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:-
The invention relates to systems of distributing and regulating alternating
currents.
The object of the invention is to provide a method of and means for varying the
lag of the current in an alternating current circuit and thereby neutralise the
self induction of the circuit so that the generator can work at its maximum speed
and efficiency.
The improved method of varying the lag of a current in alternating current
circuits depends on the fact that if an electromotive force opposite in direction to
the impressed electromotive force be introduced the lag of the impressed current
will be reduced as the new or back electromotive force increases. According to
the present invention an electric motor is placed in the alternating current circuit
the field magnet of said motor being excited from another source, and then by
increasing the excitation of this field magnet the back electromotive force of the
motor is increased, and the lag of the current in the circuit reduced, that is to say,
to a certain extent the effect of the self-induction in the circuit is neutralized.
Furthermore, the reduction of the lag brings the current more into step with the
impressed electromotive force, and thereby acts to decrease the armature reaction
of the generator, and this decrease of armature reaction will of course act bene-
ficially on the field magnet and so increase the output of the generator. It will
be also remarked that the practical neutralization of the self induction will, if the
alternating current circuit be supplying a work circuit either through a trans-
former or otherwise, increase the potential difference at the terminals of such work
circuit.
In order that the invention may be clearly understood we will proceed to explain
how it may be carried into practical effect in a system of distribution in which
alternating currents are converted by a rotary transformer into direct currents
which are supplied to the translating devices. In such a system the alternating
side of the rotary transformer may be considered as an electric motor, and variation
in the excitation of the field magnet of the rotary transformer will operate to vary
the lag of the current in the alternating circuit.
In the drawings filed with the Provisional Specification the rotary transformer
has a field magnet which is wound with both shunt and series coils for the purpose
of varying the excitation. The current in the series coil will of course vary with
the load in the direct current circuit.
Figure 1 is a diagram of circuits and machines so arranged that the injurious
effects of self-induction in the generating circuit are neutralized.
Figure 2 is another diagram of a system of distribution in which the electro-

page_text: motive force supplied to the direct current circuit is automatically adjusted
according to the load on the circuit.
Referring to Figure 1, 1 is a two phase alternating current generator the armature
of which is provided with an inter-connected winding 2. 3 is the field magnet
winding excited by current from a suitable exciter 4. The armature winding is
tapped at four points, and two circuits for each phase are connected to the winding,
as indicated. Step up transformers 5 and 6 are supplied with currents of one
phase, and step up transformers 7 and 8, with currents of a phase differing 90°
therefrom. The secondary of the transformer 5 is connected with a transmission
circuit 9, 10, the secondary of the transformer G, with a similar circuit 11, 12, the
secondary of the transformer 7 with the circuit 13 and 14, and the secondary of
transformer 8 with the circuit 15, 16. 17 is a step down transformer the primary
of which is connected with the cirouit 9, 10, and 18, 19, and 20 are similar trans-
formers respectively connected with the several transmission circuits 11--12,
13-14, and 15-16. The secondaries of the transformers 17 and 19 supply current
to the alternating current end 21 of a rotary transformer 22, and the secondaries
of transformers 18 and 20 are similarly connected to the alternating current end 23
of a rotary transformer 24. The field magnets of these rotary transformers 22
and 24 are respectively provided with shunt coils 25 and 26 and series
coils 27 and 28. The current from the direct current ends 29 and 30, respectively,
of the rotary transformers 22 and 24, is supplied to the mains 30 in the usual
The armature construction of the rotary transformers is not illustrated,
it being understood that it may be of any suitable character known in the art and
provided with either a single winding or a plurality of windings.
In a system of apparatus and circuits like that shown and described, the usual
effect of the compound winding for the field magnets of the rotary transformers
obviously depends upon the presence in the alternating current circuits of more
or less self-induction; in fact the unavoidable presence of self-induction in such
circuits is recognised, and it is the object of the present invention to provide a
means whereby the injurious effects of such self-induction may be obviated. If
the field magnet windings of the transformers are properly proportioned and
adjusted the circuit through the series coils will increase as the load upon the
circuit 30 increases, thus strengthening the field and accelerating the phase of
the lagging currents in the alternating current circuits supplying the transformers
until the currents and corresponding electromotive forces are brought substantially
into step, thus supplying the maximum amount of real energy to the transformers
and reacting upon the generator 1 so as to bring its current and electromotive force
waves into step with each other, and thus reduce the armature reaction sufficiently
to give a materially increased output over what would be secured if the self-
induction of the alternating current circuit were permitted to have its usual effect
upon the current flowing through the circuit.
Referring now to Figure 2, 31 is a rotary transformer the armature of which
may have one or two windings as may be desired. 32 represents the shunt field
magnet winding and 33 the series field magnet winding, and 34 and 35 direct
current feeders supplying mains 38 and 39. Translating devices receiving
currents from said mains are shown at 40, 41 and 42. Any other desired arrange-
ment of translating devices and circuits may obviously be employed 43 and 44
are stationary step down transformers or converters the primaries of which are
respectively connected with the cirouits 45 and 46, and 47 and 48, supplied with
current from a two-phase generator 49. It will be understood that in cases where
the generator potential is not too high, the rotary transformer may be supplied
directly therefrom without the interposition of step down converters. In each
alternating current circuit supplied by the secondaries of the converters 43 and 44
or by the generator directly as the case may be, is a choke coil 50. These coils may
5 if desired however, be included in the circuit supplying the primaries of the
converters 43 and 44, and in some cases such converters may themselves include
sufficient inductive resistance to provide the necessary difference of potential

page_text: between the generator and the transformer. The transformer field magnet
windings and the inductive resistance represented by the choke coils 50 will be
adjusted for each particular organisation of apparatus; but when once adjusted for
any special case, they have a constant value.
I have illustrated the invention as applied to a two-phase system of distribution
but it will be understood that it is equally applicable to single phase systems or to
those having a greater number of phases than two. Where choke coils are
employed, as will usually be necessary in order to secure the desired inductive
potential drop, they will be so proportioned that there will be no saturation of
their cores under any conditions. As the inductive drop due to the choke coils is
diminished by the strengthening of the field under an increase of load and the
current is brought more nearly into step with the electromotive force impressed
upon the circuit by the generator 19, the effective electromotive force supplied by
the rotary transformer to the direct current circuit will be kept up to the desired
value. The inductive resistance and the field coils of the transformer may be
made so that the current and electromotive force will be brought into step under
any desired conditions of load depending upon the conditions of the plant in
connection with which the invention is employed and the results sought to be
secured thereby.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed as communicated to
me by my foreign correspondents I declare that what I claim is:-
1. The method of varying the lag of the current in an alternating current
circuit by altering the magnetic field and thereby the back electromotive force of
a motor or rotary transformer connected in said circuit.
2. A system of distribution of alternating currents in which is provided an
electric motor having means for varying the excitation of its field magnet whereby
the lag of the current in the mains may be varied and the effect of self-induction
in the circuit neutralised if desired.
3. A rotary transformer having its field magnet wound with both a shunt coil
and a series coil for the purposes specified.
4. In a system of electrical distribution by alternating currents which are con-
verted by a rotary transformer into direct currents which are supplied to the
translating devices, the provision of means for automatically maintaining constant
the voltage of the direct current mains.
5. Systems of electrical distribution arranged as described with reference to the
accompanying drawings.
Dated this 23rd day of August 1897
W. P. THOMPSON & Co.,
Of London, Liverpool, Manchester and Birmingham,
Patent Agents for the Applicant.