Improvements in Methods of and Means for Regulating Alternating Current Dynamo-electric Machines or Distribution Systems.
Year: 1897

page_text: Date of Application, 14th Dec., 1897-Accepted, 29th Jan., 1898
Improvements in Methods of and Means for Regulating Alternating
Current Dynamo-electric Machines or Distribution Systems.
We, THE BRITISH THOMSON-HOUSTON COMPANY LIMITED, of 83, Cannon Street,
in the City of London, Electrical Engineers, do hereby declare the nature of this
invention (which has been communicated to us from abroad by Edwin W. Rice,
Junior, of Schenectady, in the County of Schenectady, State of New York, United
States of America) and in what manner the same is to be performed, to be
particularly described and ascertained in and by the following statement:-
The present invention relates to improved methods of and means for regulating
dynamo-electric machines or distribution systems, and comprises a number of novel
steps and features capable of being applied in a wide variety of ways.
The particular application of these novel features which will be described herein-
after, at length, is a mode of regulating or compounding alternating current
dynamo electric machines whose field coils are energized by an exciting machine
without the necessity of commuting the whole or any portion of the main current,
as has heretofore been the practice; and furthermore, compounding or compen-
sating not only for changes of current under different conditions of load, but also
for changes in the phase relation of current and electro-motive force which arises
from time to time in alternating current distribution systems from various causes
well known to electrical engineers.
It is well known that when the load on any dynamo electric machine, acting as
a generator, increases, the resistance-drop also increases, and the terminal voltage
falls. The voltage at any distant point on the distribution system falls at the
same time, and to an even greater extent. But where alternating current
generators are used, any change in the phase relations between current and electro-
motive force in the main circuit of the machine causes a change in the voltage at
any point in the system. Our correspondent understands this action to be due to
several causes, of which the most important are: first, an increase of lag tends to
increase the drop due to self-induction in the armature; and, second, an increase
of lag tends to increase the armature reaction.
With constant internal electromotive force, and with any given positive amounts
of resistance and self induction in the armature, the terminal voltage of the
machine will be different from, and usually smaller than, the internal electro-
motive force. The terminal voltage will also, in general, lag behind the internal
electromotive force. It is therefore necessary, in order to maintain constant
voltage at the brushes, to increase the internal electromotive force with any increase
of load or of lag in the main circuit, and to decrease it with any decrease of load or
of lag. Furthermore it is necessary, up to a certain point at least, to decrease the
internal electromotive force with any increase of lead in the main current, for any
small lead of the main current in advance of the terminal electromotive force of
the machine will only tend to bring it more nearly in phase with the internal
electromotive force, and thus reduce the inductive drop of the armature and the
armature reaction.
In the above discussion it has been assumed that straight compounding is

page_text: desired. But it is well known in the art that it is often desirable to obtain
over-
compounding." That is to say, it may be desirable to maintain constant voltage
at any selected point in the system. If this point is at the brushes of the gene-
rator, the compounding is straight; if this point is at any distance from the
brushes, as for example at the translating devices or at some selected point in
the net-work, the machine is said to be adjusted for "over-compounding." In the
first case we have to consider only the resistance and reactance of the machine,
while in the second case the resistance and reactance of the transmission lines up
to the selected point, as well as the effective resistance and reactance of the step-
up transformer, (if one be used) must be taken into account. It will appear later
that this invention is equally applicable to either of these needs.
Briefly stated, the specific method of compounding described and illustrated in
this application consists in passing the current. of the main machine by suitable
electrical inductive connection through the armature or current generating member
of the exciter, thereby producing in the exciter armature alternating polarities
which reverse in synchronism with the movements of the armature in space across
its field poles. By the reactive influence upon the field of the exciter of the alter-
nating current thus fed through its armature, the resultant field magnetism of the
exciter, and consequently its voltage is varied automatically from time to time, so
that the current derived from its commutator, and used for exciting the field of
the main machine, preserves the field magnetization of the main machines of such
value as renders the machine self-regulating under varying conditions of load.
In some instances the result to be secured will make it advisable to pass through
the exciter armature not the main current of the machine but a current propor-
tional to the voltage of the machine. In the one case, the main current or a
ehunted portion of the main current, is fed to the armature of the exciter, in the
other case the armature of the exciter will be included in a shunt circuit across the
brushes of the main machine or the circuit wires connected thereto.
It is, however, not intended to limit the scope and novelty of this invention
solely to such a method of compounding separately excited alternators as has been
outlined, since the invention comprises radically novel features which are useful
in many other systems and combinations. Prominent among these is the mode in
which the exciter, considered simply as a dynamo machine apart from its combina-
tion with the main alternator, is regulated; secondly, the automatic regulation of
dynamo machines or systems so as to compensate for the effects of lagging and
leading currents in the external circuit.
Heretofore it has been customary to regulate dynamos in various ways; for
example, by a resistance in series with or in shunt around the field circuits or by
shifting the brushes or by other ways, which need not be mentioned.
In the system now proposed regulation is secured automatically by the reactive
influence upon the field of the machine of an alternating current which is caused
to flow in its armature, and the expedients which have heretofore been resorted to
may be dispensed with altogether, or at all events, used simply as auxiliaries to
the novel method of regulation just mentioned. It is evident that a dynamo so
regulated may be used for many other purposes than to excite the field of a second
machine, and hence the novelty of this part of the invention is by no means con-
fined to the combination of a main generator and exciter which mutually serve to
regulate each other.
Furthermore, it has heretofore been proposed to compensate the effects of lead-
ing and lagging currents in an alternating current system by special phase
controllers by which the phase relation of the current and electromotive force may
be varied at will.
In the present invention the effects of changes in the phase relation of current
and electromotive force are corrected by regulating the main machine. For
example, if the current in the circuit of an alternating generator lags behind the
impressed electromotive force at the terminals of the machine, the potential will
become less than it would be under the same conditions were the current in phase

page_text: with the electromotive force; on the contrary, if the current becomes leading,
the potential will tend to rise. A distinctive feature of this invention is that the
generator in such cases may be automatically regulated to correspond with the
various phase relations existing in the circuit under different conditions, so that
should the current fall out of phase, and become lagging, such a change of itself
brings about directly or indirectly the necessary regulation of the generator to suit
the condition assumed. The same holds true if the current becomes leading instead
of lagging. This result generically stated, is secured by including in the circuit
of the machine an electro-responsive device of such character that it takes cognis-
ance, so to speak, of the existing phase relation at a given time, giving one response
or producing one effect when the current lags, and a different response or different
effect when the current leads. These secondary effects are utilised to regulate,
or control the regulation of, the generators or other apparatus requiring regulation..
In the specific apparatus hereinafter described, the electro-responsive device
answering this purpose is the exciter dynamo, which, as will be explained, raises
the voltage of the main dynamo when the current lags and reduces the voltage
when the current leads. It is however, evident that the same function can be
secured by other apparatus and utilized in a variety of combinations in which the
electro-responsive device is coupled either in series or in shunt relation to the
circuit, so that such of the claims hereinafter made as relate to this part of
the invention are intended to be generic.
The
In the embodiment of the different features of the invention specifically
described hereinafter there is provided a main alternator, which is assumed to be
a generator feeding a distribution system, through motors, rotary converters, or
electro-dynamic phase controllers may be regulated in a similar manner.
main generator may be constructed in any ordinary manner. A continuous
current exciter of any ordinary description furnishes current for exciting the field
magnets of the main machine. This exciter not only provides a proper excitation
for the alternator under its regular or normal load, but it varies the excitation
automatically under different conditions in accordance with the ordinary
principles of compound winding, as these terms are ordinarily understood
in the art, so that as the load increases the potential also increases correspond-
ingly, or, if preferred, in a greater ratio, as in the case of over-compounded machines.
It is therefore possible to dispense with the commutator heretofore employed for
rectifying the whole or a part of the current of a machine in order to make it self-
compounding, together with all accessory devices for suppressing sparking, and so
on.
The simplest arrangement is to provide the main alternator with a single field
winding, and to use only a single exciting machine, which therefore plays the part
both of the ordinary exciter and of all special means for compounding. It is, however,
quite possible to supply the initial field magnetization for the alternator from one
source of current supply, and the varying excitation, necessary for compounding,
from a separate regulated machine. The exciter comprises an armature with a
series closed-coil winding and commutator of any ordinary pattern, and the field
magnet of the exciter, when the machine is to run at the same speed as the main
generator, should have the same number of poles as the main machine. It is,
however, only essential that the number of poles of the two machines and the
speeds at which they are driven should be such that from an electrical standpoint
the machines run in synchronism with one another, so that the alternations of the
current from the main generator are in step with the movement of the exciter
armature across its poles. The current induced in the armature of the exciter is
rectified by a commutator and excites its own field magnets and also the field
magnets of the main machine, as has heretofore been customary. The current in
the main generator is passed through the armature of the exciter, and in so doing,
developes alternating polarities therein which react upon the field magnetization of
the exciter, and so vary its voltage. The amount of this reaction and the con-
sequent regulation secured will correspond with the strength of the main current
passed through the armature, and also the phase relation of the current.
1

page_text: The connections between the armatures of the two machines are so made that
the polarities induced in the exciter armature are of opposite sign to the adjacent
field poles at any given instant and somewhat ahead of the exciter field magnetiza-
tion. The result is that with increasing main current the current passing through
the exciter armature strengthens to a correspondingly greater degree the exciter
field, and thereby the excitation of the main alternator. If the current lags, as
under an inductive load may occur, the magnetization produced by the alternating
current passed through the exciter armature comes more nearly in line with
the exciter field magnetization, thus strengthening its field more and increasing
the excitation of the alternator; while, on the contrary should the current lead, the
magnetization of the exciter armature, due to this current, is less in line with
that of the exciter field, and thereby strengthens it less, or may even be in
opposition to the exciter field and so weaken it.
In some cases the arrangement may be such that the polarities induced in the
armature of the machine regulated by armature reaction, will be of like sign to
the adjacent field poles, so that regulation is due to the differential rather than the
cummulative action of the magnetic fields; the armature poles in this case weaken-
ing instead of strengthening the field poles. Such an arrangement is specially
desirable in constant current machines or systems, while the former arrangement
is better adapted to constant potential machines. If the machines are properly
proportioned, the regulation secured in this manner may be entirely automatic,
though adjustable resistances may be used in the field magnet circuits of the
machines as auxiliaries in securing the desired regulation, or correcting the effects
of imperfections in design or for adjusting the machines for different ratios of
compounding.
When the exciter has the same number of poles as the main machine; the two
machines may be driven in synchronism by mounting their armatures upon the
main shaft, or by running the armature of the exciter by a synchronous motor or
by the alternating current from the generator itself, after the manner of a rotary
converter. The alternating current of the main machine is passed through the
armature of the exciter, either by direct electrical connections or indirectly
through the transformer or other inductive apparatus.
The accompanying drawings show embodiments of this invention. Fig. 1 is
a diagram of an alternating generator and exciter and connections therefor con-
structed and arranged according to the said invention, the exciter armature being
understood to be upon the same shaft as the armature of the main generator;
Fig. 2 is a sectional elevation of an arrangement similar to the above
except that a transformer is introduced between the main alternator and
the exciter armature; Fig. 3 shows a modification wherein the exciting
armature is synchronously driven by derived current from the line, and need not
be upon the same shaft; Fig. 4 shows a modification; Fig. 5 shows diagrammatic-
ally a further modification illustrating particularly a way in which the regulating
effect of the main current upon the exciter may be controlled, and Figs. 6, 7 and 8
are diagrams explanatory of the mode of operation of the invention.
In Fig. 1 G represents an alternating current generator, having armature coils A,
field magnet coils F, and collector rings 2, the latter being shown upon the left
side of the drawing, for clearness of illustration. Upon these rings bear the
brushes 13 B, connected to the line wires 12, between which translating devices
´of any desired character are designed to be coupled in parallel. The field magnet
coils are shown wound to produce alternate poles in the usual way. S is the shaft
of the generator, and upon this shaft is fixed the armature a of the exciting
machine E, which machine also has field magnet coils f wound to produce alternate
poles, and in this particular embodiment of the invention equal in number to the
number of the poles of the alternator G. C is a commutator on the shaft S con-
nected to the windings of the armature a, which are of the multipolar type corres-
ponding to the number of pairs of poles of the field, and, in the case illustrated, a

page_text: series winding adapted to twelve poles. Upon the commutator C bear the
brushes 61, 62, at points of opposite polarity, and from these brushes connections 34
lead from the brushes to the field magnet coils of the alternator and of the exciter
which, as illustrated, are in series, but may be equally well in multiple. The com-
mutator and brushes may be connected and arranged as is customary in any
continuous current machine of this type.
When the shaft is rotated, the exciter will act as an ordinary multipolar, direct
current generator and will build up until the designed electromotive force is
developed; this force may be adjusted to the proper amount by the regulating,
resistance R included in the circuit of the field magnet coil f. The field magnets F
of the alternator are at the same time excited and an alternating electromotive
force is generated between the lines 1, 2, the amount of current flowing depending
upon the load; as the load increases it becomes necessary to increase the excitation
of the field magnets F, that is, compound the machine.
This result is obtained by passing the line current through the armature a,
as shown by the connections from the main armature to the collector ring r², which
tap the exciter armature winding at the points ?, p¹. It is of course to be under-
stood that this tapping may be accomplished either by collector rings where the
two machines are not mounted upon the same shaft, or by direct connection (which
is to be preferred, if convenient) where the exciter armature is upon the same shaft
with the alternator.
It is shown in dotted lines at 7-7 that the field magnets of the two machines
may be arranged in multiple; and the switch s may be employed to close the shunt
circuit G in order to build up more rapidly the field of the exciter machine.
In many cases it will be preferable to effect an inductive transfer of the alternat-
ing current in order to facilitate controlling or varying the regulating effect of the
main current upon the exciter and to permit of winding the exciter for current of
comparatively low voltage. One such arrangement is illustrated in Fig. 2,
wherein the letters refer to the same parts as in Fig. 1; but there is also shown in
addition to the apparatus in Fig. 1, a transformer T, the primary coil t of which is
connected in the circuit of the armature A, and its secondary t¹ is connected to the
armature a. Except as to this intermediate transformation, which may be of any
character desired by the engineer, the arrangement and the action are the same
as in Fig. 1.
In Fig. 3 is shown a modification wherein the exciter armature may be upon a
separate shaft from the alternator and be driven by current taken from the main
line by the derived circuit 8, 9, the armature being understood to run synchron-
ously, and if the number of poles in the exciter be less the speed being correspond-
ingly greater.
Two transformers are indicated in this figure, and they may be considered as
in effect a single transformer,, inasmuch as the secondary coils in circuit with the
armature a are in series with one another. In this case, however, the primary of
the transformer T¹ is in series with the armature A, while the primary of the
transformer T is in shunt across the mains 12, from the alternator G. The opera-
tion of the transformer T will therefore depend upon the current from the
armature A, while that of the transformer T2 will be dependent upon the potential
between the mains 12, as is well understood.
In Fig. 4 it is shown that the interpolation of the exciter armature may be made
at any point in the winding of the armature of the main generator, and that it
is not necessary that it should be between one of the collector rings and the end
of the winding, as the same effect can be obtained by its insertion in other places,
the arrangement of Fig. 1 being simply the preferred arrangement.
In Fig. 5 an arrangement is shown somewhat similar to that of Fig. 2, and in
this figure corresponding parts are indicated by the same letters of reference as
heretofore described. The main alternator G and the exciter E are driven
synchronously by belts passing around the pulleys P, P from the shaft K, or in
any other manner. The current from the main alternator is fed to the armature

page_text: of the exciter through a transformer T, and the secondary winding of the trans-
former is divided into sections, more or less of which may be brought into circuit
by a switch s. In this manner, as will be readily understood, the current trans-
formed and passed through the exciter armature, may be regulated, and inasmuch
as the regulating effect of the current on the exciter varies with the strength of
the current, the arrangement indicated furnishes a convenient means for manual
regulation, or even for automatic.
Figs. 6, 7 and 8 are intended to be explanatory of what our correspondent at
present conceives to be the mode of operation of this method of regulating dynamo
electric machines. In these Figures 1, 2, 3 and 4 represent the field poles of the
exciter, which are alternately of a north and south polarity, as indicated. 5, 6, 7
and 8 represent poles on the exciter armature, which, it is assumed, is to rotate
across the field poles to the left, as is indicated by the arrow. The alternating
currents are tapped into the armature, preferably so that the polarities induced in
the poles are of opposite sign to the adjacent field poles, as represented by s, n,
and the adjustments are such that these polarities become a maximum just before
the armature poles stand opposite to the adjacent field poles. With this arrange-
ment it is evident, that the field poles 1, 2, 3 and 4 will be strengthened by the
polarities induced in the adjacent armature poles, and that this strengthening
effect will become more or less great as variations in the strength of the armature
current strengthen or weaken the armature polarities, thus giving a compounding
effect to the exciter, and indirectly to the main alternator, which corresponds
with the current generated in the main alternator. If, now, the current lags, the
polarities induced in the armature will reach a maximum an instant later than
when the currents are in phase, as is assumed to be the case in Fig. 6. Hence, at
the time the armature polarities reach their maximum the poles 5, 6, 7 and 8 will
be more nearly in line with the poles 1, 2, 3 and 4, thereby strengthening the field
poles to a greater degree, and raising the potential of both the exciter and main
machines. This is shown in Fig. 7. If, on the other hand, the current leads, the
armature polarities will reach a maximum when the poles 5, 6, 7 and 8 are less in
line with the corresponding field poles, as indicated in Fig. 9, and their strengthen-
ing effect upon the field poles will be less than in the position shown in Fig. 6.
In this way, the potential of the exciter is automatically lowered and the potential
of the main machine lowered correspondingly.
It will be seen that the amount and character of the compounding depends upon
the relative proportioning of the various parts etc., and upon the angle at which the
main circuit enters and leaves the exciter armature.
It is obvious that the novel features herein described and referred to in the
claims, are applicable to multiphase machines and systems as well as to the single
phase machines and by reason of the complication of the compounding arrange-
iment in multiphase systems, are even more desirable. In such cases the arrange-
ment shown in Fig. 1 is extremely desirable; and may readily be adopted, the
only difference being such as would exist in the machine itself; the armature
winding A being branched into several coils and the connection from the exciter
being made to the common connection or junction, or rather, the exciter armature
may be made to serve the purpose of this common connection or junction.
766
Where parts are referred to as being "connected" it may mean either directly
connected or connected through transformation. The term commutator" is also
used in a broad sense as a rectifying device, and should, when so used, be taken to
include both the commutator proper and the brushes co-operating with the same.
And furthermore, in using the term alternating" it is intended to include multi-
phase alternating currents as well as single phase currents; since there is no
intention to limit the claims in this case to the single phase current, but on the
contrary, the purpose is to include multiphase systems within the scope of the
claims.
In the claims the term "alternating current machine" is employed, and such
term is meant to include any synchronising alternating machine, whether generator

page_text: synetonous motor, rotary transformer or compensator, either generating, utilizing
or controlling alternating currents of one or many phases, the modifications attend-
ing the employment of the above described improved method in such cases being
apparent to electrical engineers such, for instance, as that compensation for lead
and lag in the current is reversed in a synchronous motor with reference to the
direction of compensation in a generator.
Having now particularly described and ascertained the nature of the said in-
vention (as communicated to us from abroad) and in what manner the same is to be
performed, we declare that what we claim is:-
1. The combination of an alternating current generator an exciter, having an
armature and field magnet independent of the corresponding elements of the
generator, means for driving said exciter, and means for superposing on the
current in the armature of the exciter a current of a magnitude and phase varying
in accordance with the magnitude and phase of the current from the main
generator, and thereby regulating the said main generator both for inductive drop
and resistance drop.
2. The combination with an alternating current generator of an exciter therefor,
and means for superposing upon the current in the armature of the said exciter
a current varying in magnitude and phase in accordance with the current in the
main generator, the connections by which the said current enters and leaves the
exciter armature being made at such points that any increase in the lag of
the current in the main circuit will add to the exciter voltage.
3. The combination of a dynamo electric machine, comprising field magnets and
a commutated armature having a single armature winding, with a source of alter-
nating currents, and means for passing through said armature alternating currents
from said alternating source, whose alternatious are synchronous with the magnetic
phase induced in said armature by its field magnets, substantially as set forth.
4. The combination of a dynamo electric machine having an armature which
revolves in a magnetic field, a source of alternating current, and means for con-
necting said source of current with the armature winding of said dynamo machine
at such points that the polarities induced in the armature by the alternating
current are of opposite sign to the adjacent field magnet poles and somewhat ahead
of the magnetisation induced in the armature by its own field magnets, substan-
tially as set forth.
5. The combination with the field magnets and armature of an alternating
current machine of an exciter machine comprising an armature, field magnets and
a commutator, the commutator being connected to the armature winding of the
exciter and delivering current to the field magnet systems of both the main alter-
nator and exciter, and connections from the armature of the main alternator to that
of the exciter for passing the current of the main machine through the armature
of the exciter, substantially as set forth.
6. The combination of an alternating current dynamo electric machine, with an
exciter having a commutated armature connected with the field coils of the main
machine, and a transformer whose windings are respectively in circuit with the
external circuit of the main machine and with the armature of the exciter.
7. The combination of an alternating current dynamo electric machine, with an
exciter machine, and inductive apparatus connecting indirectly the armature
circuits of the two machines, and means for varying the current through said
inductive apparatus, substantially as set forth.
8. The method of regulating an alternating current dynamo electric machine
which consists in causing the main current to strengthen the exciting current with
an increase of lag, and to weaken it with an increase of lead.
9. The method of regulating an alternating current dynamo electric machine,
which consists in automatically increasing its internal electromotive force with any
positive increase of lag of the current passing through the machine, and decreasing
its internal electromotive force with any negative increase of lag.

page_text: 10. The method of regulating a dynamo electric machine, which consists in
automatically increasing its field magnet excitation with any increase of load and
with any increase of lag, and decreasing its field magnet excitation with any
decrease of load and with any decrease of lag.
11. The combination with a dynamo electric machine, of a source of current
supplying exciting coils on its field magnets, and electro-responsive means con-
trolled by the circuit of the machine for increasing the exciting current with an
increase of lag or a decrease of lead, and decreasing it with a decrease of lag or an
increase of lead.