Improvements in Synchronizing Mechanisms for Alternating Current Generators.
Year: 1896

page_text: Date of Application, 17th Jan., 1896
Complete Specification Left, 19th Oct., .1896-Accepted, 16th Jan., 1897
PROVISIONAL SPECIFICATION.
Improvements in Synchronizing Mechanisms for Alternating Current
Generators.
I, HORACE FIELD PARSHALL, of 38, Parliament Street, Westminster, in the
County of London, Electrical Engineer, do hereby declare the nature of this
invention to be as follows:-
My invention relates to devices for synchronizing the phase relation of alternating
current dynamo-electric machines connected in parallel, and has for its object to
accomplish this purpose by automatically regulating the engine or prime mover
connected to the various machines. I therefore connect a suitable regulating valve,
which may be the throttle or a specially designed controller, the particular type
being unimportant, to a device such as is hereinafter referred to, but which I may
briefly call a watt-mechanism, provided with two sets of coils upon an inducing
member or field, magnet; one of these sets of coils or windings is supplied with
current from the main between the two machines to be kept in synchronism, preferably
from a series transformer in that main; the other winding is supplied by a shunt
between the circuit mains, also most conveniently employing a transformer. Within
the field of force generated by these coils is rotatably mounted a suitable induced
member or armature, using the term to designate any structure capable of transmitting
torque in such a mechanism as the one described. To this armature is connected the
engine valve before referred to, the connection being made by any preferred means.
The method of operation will be more particularly described hereinafter.
The device above indicated is capable of modification in several ways, which will
be pointed out later.
In running alternators in parallel, not only do difficulties arise in starting an idle
machine so as to throw it into circuit only when in proper phase relation, but when
the load changes upon a number of machines already running, it is difficult to make
it divide properly, without throwing the dynamos out of phase to a greater or less
extent.
The apparatus which I have devised is especially useful in this contingency,
inasmuch as it is not only automatic in its response to changing conditions, but as it
operates only by variant phase relations, the potential regulation of the machines to
effect the proper distribution of load may be independently performed by hand or
otherwise, the apparatus of my invention taking care of the phase relation so that
no energy is wasted by the electro-motive forces of the machines opposing one
another.
:
5
The drawings hereto annexed show in diagram certain ways of carrying out my
invention; Fig. 1 shows the device above referred to, and Fig. 2 is a modified
form.
In Fig. 1, A, A¹ are the alternators running in parallel between the mains or
bus-bars a, b; C, D are transformers, the primary coil of C being in series with
the main , and the primary coil D' of D being in shunt to the main circuit. C' is
the secondary coil of the transformer C, in circuit with one set of the coils upon the
inducing member or field-magnet E of the watt-mechanism already referred to; to
the other set of these coils energy is supplied froin the secondary D³ of the
transformer D. The inductance and resistance of the circuits containing the

page_text: secondaries and inducing member Ẹ are so selected that in their normal condition no
relative difference of phase exists between the energy developed in the respective
sets of coils upon the inducing member.
E is the induced body or armature, of any type suitable for the
As
purpose.
instances of proper constructions, I may mention a laminated iron "shuttle," a
so-called "squirrel-cage," or a closed-circuited armature of any other convenient
form. Upon the shaft about which the member rotates is mounted a pinion el meshing
with a rack attached to the bar F; this latter, bar is connected to a lever H,
controlling the valve K, by which the flow of steam through the pipe G is regulated.
Another valve is governed in reverse relation to the valve K by the other end of the
bar F, but is not illustrated, it being like the valve K in construction. By this means,
the engines of the two machines may be simultaneously and inversely regulated so
that the racing machine will be throttled, while the lagging or overloaded engine will
be given more steam.
Referring now to Fig. 2, I show a modified form of my invention which may be
employed, both of the particular arrangements illustrated being best adapted to two
machines. In this figure the reference letters indicate the same parts as before, the
connecting part F being omitted, as its function would be well understood. The
transformer C, however, is provided with two coils, one coil C being in the lead from
the machine A', the other, C, being in that from the machine A: This latter coil has
its terminals reversed, and consequently its electro-motive force is opposed to that in
the coil C. The electro-motive force generated therefore in the coil C3 in circuit
with the inducing member E, is normally zero, but when one or the other of the
machines leads, the current induced in C would respond to the difference of phase
between the two machines, and the actions indicated in Fig. 1 would take place.
The operation of the device as just described may be briefly stated as follows.
During the normal operation of the machines, although the entire current from the
machine A (Fig. 1) passes through the transformer C and the entire potential
across the system is measured by the transformer, D, the coils are, as before stated,
so wound that their resistance and inductance are substantially similar, and no
difference of phase exists in the two windings upon the inducing member. There
is therefore no tendency to start in the induced member E', and the apparatus.
remains stationary. Assume, however, that the machine A races, the electro-
motive forces in the transformer C become leading, or out of phase with those
in D a difference of phase is then set up in the two windings of the field-
magnet, and the armature E' responds and changes the position of the valves
already referred to. Should the machine A' speed up or the machine A drop
behind, the reverse condition takes place, that is to say, the electro-motive forces
ia the transformer C, instead of leading, would lag behind those in the transformer D,
and the armature E would then tend to move in the opposite direction. Normally
these motions would be slight, the machines naturally tending to keep in phase;
in addition, the effects of hysteresis and self-induction in the two circuits act to
some extent like a mechanical dash-pot and tend to prevent responses to small
and comparatively negligible differences which would ordinarily quickly correct
themselves.
My invention is also applicable to a station in which more than two machines
are employed. In this case it would not be necessary to employ individual shunt
transformers for each of the watt-organisms.. I may therefore employ a single
transformer with a divided secondary coil, the coil supplying all of the shunt
windings upon the various inducing members. Between each two of the machines,
. however, is a series transformer, and each of the inducing members is in the circuit
with one of the separate series transformers. In this case the engine connected to
each dynamo is controlled by one of the watt-organisins or regulators, and the
inverse regulation of the engines possible with the two machines is unnecessary
and undesirable, on account of the complication required to effect the connections.
Although I prefer to employ a single shunt transformer, my invention is not
limited in this respect, as individual transformers might be used if desired. So

page_text: also a single coil might be used as the secondary of the single shunt transformer
required, and the various inducing members might be connected to it in series or
in parallel, the winding and size of wire being properly selected so as to normally,
maintain the electro-motive forces in proper.. phase with those of the series coils,
these changes being well understood by those skilled in the. art.
Improvements in Synchronizing Mechanisms for Alternating Current
Generators.
I
I, HORACE FIELD PARSHALL, of 38, Parliament Street, Westminster, in the County:
of London, 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 ascér-
tained in and by the following statement:-
311
My invention relates to devices for synchronizing the phase relation of alternating,
current dynamo-electric machines connected in parallel, and has for its object. to
accomplish this purpose by automatically regulating the engine or prime mover.
connected to the various machines. I therefore connect a suitable regulating valve,,
which may be the throttle or a specially designed controller, the particular type being
unimportant,. to a device more particularly hereinafter described, but which I may,
briefly call watt-mechanism, provided with two sets of coils upon an inducing
member or field magnet; one of these sets of coils or windings is supplied with,
current from the main between the two machines to be kept in synchronism, preferably.
from a series transformer in that main; the other winding is supplied by a shunt
between the circuit mains, also most conveniently employing a transformer. Within
the field of force generated by these coils is rotatably mounted a suitable induced.
member or armature, using the term to designate any structure capable of trans-
mitting torque in such a mechanisin as the one described. To this armature, is
connected the engine valve before referred to, the connection being made by any,
preferred means. The method of operation will be more particularly described
hereinafter:
The device above indicated is capable of modification in several ways which will
be pointed out later.
In running alternators in parallel, not only do difficulties arise in starting an idle
machine so as to throw it into circuit only when in proper phase relatiou, but when
the load changes upon a number of machines already running, it is difficult to make
it divide properly, without throwing the dynamos out of phase to a greater or less
extent.
The apparatus which I have devised is especially useful in this contingency,
inasmuch as it is not only automatic in its response to changing con litions, but as it
operates only by variant phase relations, the potential regulation of the machines to
effect the proper distribution of load may be independently performed by hand or
otherwise, the apparatus of my invention taking care of the phase relation so that no
energy is wasted by the electro-motive forces of the machines opposing one another.
The drawings filed with my Provisional Specification and hereto annexed show in
diagram certain ways of carrying out my invention; Fig. 1 shows the device above
referred to, and Fig. 2 is a modified form.
In Fig. 1, A A' are the alternators; running in parallel between the mains or
bus-bars a b; C D are transformers, the primary coil C" of C being in series with
the main b, and the primary coil D₁ of D being in shunt to the main circuit.
;

page_text: the secondary coil of the transforiner C, in circuit with one set of the coils upon
the inducing member or field magnet'E of the watt-mechanism already referred to;"
to the other set of these coils energy is supplied from the secondary D of the trans-
former D. The inductance and resistance of the circuits containing the secondaries
and inducing member E are so selected that in their normal condition nó relative
difference of phase exists between the energy developed in the respective sets of coils
upon the inducing member.
As
E is the induced body or armature of any type suitable for the purpose.
instances of proper constructions, I may mention a laminated iron "shuttle," a
so-called "squirrel-cage," or a closed-circuited armature of any other convenient form.
Upon the shaft about which the member rotates is mounted a pinion e' meshing
with a rack attached to the bar F; this latter bar is connected to a lever H,
controlling the valve K, by which the flow of steam through the pipe G is regulated.
Another valve is governed in reverse relation to the valve K by the other end of the
bar F, but is not illustrated, it being like the valve K in construction. By this
means, the engines of the two machines may be simultaneously and inversely regulated
so that the racing machine will be.throttled, while the lagging or overloaded engine
will be given more steam.
Referring now to Fig. 2, I show a modified form of my invention which, may be
employed, both of the particular arrangements, illustrated being best adapted to two
machines. In this figure the reference letters indicate the same parts as before, the
connecting part F being omitted, as its function would be well understood. The
transformer C, however, is provided with two coils, one coil (being in the lead
from the machine A', the other, C2, being in that from the machine A. This latter
coil has its terminals reversed, and consequently its electro-motive force is opposed
to that in the coil C. The electro-motive force generated therefore in the coil Cin
circuit with the inducing member E is normally zero, but when one or the other of
the machines leads, the current induced in C³ would respond to the difference of
phase between the two machines, and the actions indicated in Fig. 1 would take
place.
The operation of the device as just described may be briefly stated as follows.
During the normal operation of the machines, although the entire current from
the machine A (Fig. 1) passes through the transformer C and the entire potential'
across the system is measured by the transformer D, the coils are, as before stated,
so wound that their resistance and inductance are substantially similar, and'no
difference of phase exists in the two windings upon the inducing member. There
is therefore no tendency to start in the induced member E¹, and' the apparatus
remains stationary. Assume, however, that the machine A races, the electro-motive
forces in the transformer C become leading, or out of phase with those in D; a
difference of phase is then set up in the two windings of the field-magnet, and the
armature E' responds and changes the position of the valves already 'réferred' to.
Should the machine A¹ speed up or the machine A drop behind, the reverse condition
takes place, that is to say, the electro-motive forces in the transformer C, instead of
leading, would lag behind those in the transformer D, and the armature E¹ would
then tend to move in the opposite direction. Normally these motions would be slight;
the machines naturally tending to keep in phase; in addition, the effects of hysteresis
and self-induction in the two circuits act to some extent like a mechanical dash-pot
and tend to prevent responses to small and comparatively negligible differences which
would ordinarily quickly correct themselves.
My invention is also applicable to a station in which more than two machines are
employed. In this case it would not be necessary to employ individual shunt trans-
formers for each of the watt-organisms. I may therefore employ a single transformer with
a divided secondary coil, the coil supplying all of the shunt windings upon the various
inducing members. Between each two of the machines, however, is a series trans-
former, and each of the inducing members is in the circuit with one of the separate
series transformers. In this case the engine connected to each dynamo is controlled
by one of the watt-organisms or regulators, and the inverse regulation of the engines

page_text: possible with the two machines is unnecessary and undesirable, on account of the
complication required to effect the connections. Although I prefer to employ a single
shunt transformer, my invention is not limited in this respect, as individual transformers.
might be used if desired. So also a single coil might be used as the secondary of
the single shunt transformer required, and the various inducing members might be.
connected to it in series or in parallel, the winding and size of wire being properly
selected so as to normally maintain the electro-motive forces in proper phase with those
of the series coils, these changes being well understood by those skilled in the art.
Having now particularly described and ascertained the nature of this invention:
and in what manner the same is to be performed, I declare that what I claim is :-
1. The art of maintaining synchronism of alternate generators separately operated
in parallel, which. consists in controlling the speeds of the different generators by
means actuated by the variations of phase relation between them, as set forth.
2. A plurality of alternating dynamos separately operated in parallel upon a
common circuit, a regulating apparatus normally idle when the machines are in
phase, but actuated by a variation of their phase relation, and means operated by
the regulating apparatus for controlling the relative speeds of the dynamos and
thereby their phase relation.
3. A plurality of alternating dynamos separately operated in parallel on a common
circuit, and a regulating apparatus comprising an inducing member having a
number of coils, some of which are supplied with electro-motive force by a series
connection with the mains, the others with electro-motive force by shunt connection
between the mains, the electro-motive forces normally in phase when the dynamos.
are in phase, and an induced member for the regulating apparatus controlling the
prime movers of the generators and tending to accelerate a lagging machine or
retard a leading machine when the phase relations of the generators vary, substan-
tially as set forth.