Improvements in Regulable Transformers and in Regulating Alternating Current Dynamo Electric Machines.
Year: 1897

page_text: Date of Application, 23rd Mar., 1897-Accepted, 22nd May, 1897
Communicated from abroad by GENERAL ELECTRIC COMPANY, Schenectady,
New York, United States of America.]
Improvements in Regulable Transformers and in Regulating
Alternating Current Dynamo Electric Machines.
1, HENRY HARRIS LAKE, of the Firm of Haseltine, Lake & Co., Patent
Agents, 45 Southampton Buildings, in the County of Middlesex, 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:-
This invention relates to regulable transformers and to exciting and compounding
alternating current dynamo electric machines; and has for its object to obviate
some of the troubles incident to this operation when accomplished in various ways
customary in the art.
In such machines as usually constructed, an external source of current for the
field-magnets is provided, usually a small exciter dynamo, and in addition to this a
part of the current of the machine is rectified and passed around the field magnets,
by which an effect like that of the series coil in the ordinary compound-wound
dynamo is produced. Difficulties are met with in commuting the current necessary
in this form of construction, especially where an ordinary rectifying commutator is
used, as the large current and oftentimes high voltage gives rise to troublesome
sparking, to heating of the commutator, and other difficulties well known to
engineers. Two commutators have also been employed, one in shunt giving the no
load excitation, the other connected in series in the main, giving the compounding
effect; but this is not only complicated, but does not compensate in the alternators
for the lag and lead of the current, which varies with the nature of the load. Two
transformers have also been proposed, one in series in the main circuit, and one in
shunt, their secondaries being connected in series with a rectifying commutator;
but in this case the secondary of the series transformer sends its current through the
shunt transformer secondary, and the latter thus acts as a choking coil in the
commutator circuit.
To obviate these difficulties I employ in my invention a transformer having
three windings, and of the general type sometimes called a "leakage transformer."
The primary winding is in shunt to the main circuit; the secondary supplies the
rectifying commutator from which the current is taken around the field-magnets of
the machine. On another part of the same core, forming a magnetic shunt between
the two coils, I wind a modifying coil in series with the mains. Between the
portion of the core upon which the coil is wound, and part of the magnetic circuit,
is an air gap; the effect of the magnetic shunt is determined by the action of the
modifying coil, as more fully hereinafter pointed out.
In ordinary single-phase apparatus at no load, the modifying coil would carry no
current, and a large part of the flux produced by the primary would pass through
the magnetic shunt. The secondary voltage would thus be considerably less than
that normally corresponding to the ratio of transformation. As the load comes on
however a larger current passes through the modifying coil, thus opposing the flux
through the magnetic shunt, forcing it through the secondary coil, and thereby
increasing the secondary voltage and the field excitation of the main machine.
The arrangement just outlined may be employed either directly to supply the

page_text: entire field-magnet excitation, or it may be used to indirectly furnish the series-coil
or compounding effect, in which latter case a separate exciter would ordinarily be
used, of any convenient form; in which case the field coil of the exciter would be
supplied with current from the commutator in the circuit of the transformer
secondary.
By my invention the opposing magneto-motive force of the magnetic shant
depends not only upon the strength of the main current in the coils, but also upon
the phase relation between the current and electro-motive force; that is to say,
such a transformer can be made to vary not only the secondary voltage, and this
in proportion to the load, but also to vary it in correspondence with the nature of
the load, or to compound for lead and lag.
In applying my invention to a dynamo of the polyphase type, for instance to a
three-phase machine, the primary coil would be connected in shunt to the main
circuit across one phase; the modifying coil would be connected in one of the main
lines, suitable resistances being interpolated in order to control the current.
Assuming that the load in this case is non-inductive, a phase displacement of thirty
degrees would exist in a three-phase machine between the modifying coil and the
primary, and thus the magnetic shunt would oppose the component of the primary
magnetic flux displaced thirty degrees. If now the current lags, the effect of the
modifying coil in opposing the primary becomes greater, opposing the magnetic
shunt flux more and increasing the excitation; while with a leading current, the
effect of the modifying coil is to oppose the primary less, thus permitting the
magnetic shunt to divert more of the lines of force and cutting down the excitation.
It is of course unnecessary to proportion the apparatus strictly for a phase
displacement of thirty degrees, which is taken merely for illustrative purposes;
any other suitable angle might be used, and such angle as may be desired can be
readily obtained by forming the modifying coil of the magnetic shunt of two coils
connected in two lines, and proportioned with proper numbers of turns to obtain the
effect desired. So also in polyphase machines, by using more than one transformer
of the general type described, all the phases may be compounded, securing a certain
average regulation for unbalanced load.
may also use the same feature of compounding for lead and lag by phase
displacement, where no such displacement normally exists in the main circuit; as
for instance, in single-phase apparatus; in which case I may secure suitable phase
displacement between the modifying coil and the primary coil, by any proper phase
changing device, such as an impedance in shunt to the modifying coil or in series
with the primary.
The application of my invention, just briefly described, to synchronous motors, is
also apparant. In a synchronous motor, for instance, of the polyphase type, a
modifying coil would be connected in the same way in one of the three main lines,
but so as to oppose more at lagging and less at leading current to vary the
excitation in correspondence with the variations of load; and in this way I obtain
any suitable compounding or over-compounding effect, not only for the motor itself,
but for the system, as where the field of the motor was automatically over-excited,
the motor acting as a condenser in accordance with well known principles.
In addition to compounding for lead and lag of the current and for variations of
this compounding by the change in character of the load, the device of
my
invention
possesses also great advantages in that a substantially constant current is provided
from the secondary for the rectifying apparatus; that is to say, if when the
commutator brushes pass over a gap, a momentary short-circuit takes place at the
commutator, the increase of secondary current and the corresponding increase of
primary current act to force more flux across the modifying gap, and thus reduce
the secondary voltage and limit the secondary current, which tends to obviate the
difficulties already spoken of in connection with the rectification of the main
current.
I have illustrated my invention in the accompanying drawings, in which
Fig. 1 is a diagrammatic view of a single-hose machine provided with me

page_text: exciting and compounding apparatus, in which the field magnet excitation is
furnished directly from the transformer; Fig. 2 is a similar view employing a
separate exciter;
Fig. 3 is a diagram of a three phase generator and a synchronous motor connected
therewith, the machines being both supplied with exciting current by means of my
invention, and
Fig. 4 is a diagram of a modification in which all of the phases are compounded,
giving a compounding effect for unbalanced loads.
In Fig. 1, A is the armature of a single-phase alternating current generator;
B, B are the field-magnets of the machine; C, C are the collecting devices for the
mains a, b; the field-magnets B, B are supplied with current from the collector
rings C¹, each of which is connected to one side of the rectifying commutator D.
I is an ordinary transformer supplying lamps L, diagrammatically indicating any
form of load whatever.
E is the transformer to which I have referred in my statement of invention,
provided with a primary coil F in shunt between the mains a, b, and provided with
a resistance R in series therewith. F is the secondary coil in circuit with the
rectifying commutator D. G is the modifying coil interpolated in the main b,
and R' is a resistance in shunt to the modifying coil, by the regulation of which
the amount of compounding may be adjusted. H is the air gap, the central arm
of the transformer core forming the maguetic shunt to which I have referred.
It will be understood that the regulation of the primary F by means of the
resistance in series therewith acts directly to control the output of the machine,
while the regulation of the resistance R' serves to change the ratio of compounding
by passing more or less of the series current through the modifying coil G.
Referring now to Fig. 2, I show the same parts as in Fig. 1, they being indicated
by the same letters, except that in Fig. 2 a separate exciter furnishes current to
the field-magnet B of the main machine, its own field-magnet winding being
supplied from the rectifying commutator D through the collecting device C¹, the
current being supplied as before from the secondary coil F¹ of the transformer E
arranged as in Fig. 1. In this figure I also show an impedance K, consisting of
a reactance in series in the primary coil F. The action of this is to displace the
phases of current in the primary coil F and the modifying coil G; the amount of
this impedance is selected to give the desired displacement of phase. Ordinarily
the difference in the windings of the two coils would give currents of displaced
phase, it being understood that the winding F is a fine winding of high self-
induction, while G is a coil of larger wire and of few turns; but to obtain the
desired phase relation the difference of inductance or reactance might not be
sufficient, in which case the auxiliary impedance K would he employed; the electric
actions having already been pointed out in my statement of invention, and resembling
those existing in the polyphase machine, will not be further referred to.
Referring to Fig. 3, I illustrate three-phase apparatus, the parts being relatively
the same as those in Fig. 1. In this case however the coil is in shunt between
two of the mains and has, as before, a resistance in series therewith. The modi-
fying coil G is in series in the lead c and the resistance R¹ is in shunt as before.
In this construction the field magnet B of the machine might be supplied with
current from a separate exciter, arranged as in Fig. 2, without departing from my
nvention.
In the lower part of Fig. 3 is shown a synchronous motor of the three-phase
ype, A¹ being the armature, B2 the field; but in this case the modifying coil is
livided into two parts, G¹, G¹, which are interpolated respectively in the leads a, b,
nd each of which is provided with a shunting resistance, respectively lettered R¹
nd R. In a three-phase or two-phase or other polyphase apparatus this
onstruction might also be applied to a generator with good effect.
In Fig. 4 I have shown a modified form of my invention. In this I employ
hree transformers E', E2, E³, of the same general description as those already
lustrated, and a three-phase machine is compounded by means of these.

page_text: transformers; the modifying coils are in series in the three mains a, b, c, upon, the
respective transformers; the primary coils F are in shunt between the mains of
different phase, and the secondary coils F2, F3, F are combined in three-phase
relation, leads therefrom going to the segments of the commutator D, which in
this case is a three-part commutator provided with the usual overlapping arrange-
ment of brushes, indicated at D1, D2, by which all of the segments of the
commutator are at all times maintained in circuit. This arrangement thus utilizes
all of the phases, and gives an average compounding effect for an unbalanced
load.
In the claims annexed to this specification, I have spoken of utilizing the
resultant current in the secondary circuit as a means of energizing the field magnets
of the alternating dynamo; I mean to include in this and such substantially
equivalent expressions as may occur in my claims, both an indirect utilization, such
as by the exciter dynamo, and a direct, as by passing the rectified secondary current
through the field magnet windings on the main machine, and this whether the device
be employed for compounding in conjunction with some other source of current or
for the entire excitation. So also the synchronous motor is not excluded from my
invention, though its principal utility is found in generators.
Having now particularly described, and ascertained the nature of the said inven-
tion, and in what manner the same is to be performed, as communicated to me by
my foreign correspondent, I declare that what I claim is:
1. A transformer having primary and secondary circuits wound on its main core,
a core forming a magnetic shunt to the part of the core on which the secondary is
wound, a coil through which a variable current flows wound on said magnetic shunt
core, said current variably controlling the number of lines of force diverted from
the secondary circuit through said magnetic shunt in inverse ratio to the demands
on said secondary circuit.
2. A transformer having primary and secondary circuits wound on its main core
which is of the closed magnetic circuit type, a core forming a magnetic shunt to
the part of the core on which the secondary is wound, and a coil through which a
variable current flows wound on said magnetic shunt core, said current variably
controlling the number of lines of force diverted from the secondary circuit
through said magnetic shunt in inverse ratio to the demands on said secondary
circuit.
3. A transformer having primary and secondary circuits wound on its main core
which is of the closed magnetic circuit type, a core forming a magnetic shunt to
the part of the core on which the secondary is wound, said magnetic shunt core
having an air gap therein, and a coil through which a variable current flows wound
on said magnetic shunt core, said current variably controlling the number of lines
of force diverted from the secondary circuit through said magnetic shunt in inverse
ratio to the demands on said secondary circuit.
4. A transformer having primary and secondary circuits wound on its main core,
a core forming a magnetic shunt to the part of the core on which the secondary is
wound, and a coil in circuit with one of the primary mains wound on said magnetic
shunt core, the current in which coil variably controls the number of lines of force
diverted from the secondary circuit through said magnetic shunt in inverse ratio to
the demands on said secondary circuit.
5. In a system of electrical distribution, a transformer having its primary
connected in parallel with the mains of the system, and secondary circuits wound
on its main core, a core forming a magnetic shunt to the part of the core on which
the secondary is wound, and a coil in series with one of the primary mains, wound'
on said magnetic shunt core, the current in which coil variably controls the number"
of lines of force diverted from the secondary circuit through said magnetic shunt
in inverse ratio to the demands. on said secondary circuit.
6. In combination, a source of alternating current, lines leading therefrom, and
a transformer connected to the lines comprising primary and secondary coils, a

page_text: magnetic shunt, a series coil upon the shunt opposing the passage of magnetic lines
through the shunt, and a commutator in circuit with the secondary coil of the
transformer.
7. In combination, an alternating current dynamo electric machine, and a
transformer in the circuit thereof supplying its field-magnet excitation through
a rectifying commutator; the transformer comprising a core, a primary winding in
shunt to the alternating current mains, a magnetic shunt provided with a modifying
series winding, the currents in which are of phase normally displaced relatively to
those in the primary, and a secondary winding whose induction is compounded by
the joint effects of the primary and modifying windings.
8. The combination of an alternating current circuit, with a transformer com-
prising a core forming a closed magnetic circuit, and an intermediate magnetic
shunt with a primary coil connected across the circuit mains, a secondary coil, and
a modifying coil around the magnetic shunt in circuit with one of the circuit mains
and arranged so as to neutralize the effect of the shunt and increase the induction
in the secondary coil on increase of current in the main circuit.
9. The combination of an alternating current dynamo electric machine, mains
extending therefrom, and a transformer comprising a primary coil in shunt to the
mains, a magnetic shunt carrying a modifying coil or coils in series with the
mains, and a secondary coil supplying the field magnet excitation of the main
machine.
10. The combination of a dynamo electric machine of the alternating current
type, mains leading therefrom, a transformer furnishing the field-magnet excitation
of the machine, the transformer comprising primary coils in shunt to the mains,
secondary coils in inductive relation to the primary, a magnetic shunt in the
transformer, and modifying coils in series in the mains, and determining the effect
of the shunt, with means for varying the effect of the modifying coils.
11. A dynamo electric machine of the alternating current type, mains extending
therefrom, a transformer connected with the mains and furnishing field magnet
excitation for the machine, the transformer comprising primary coils in shunt to
the mains, a secondary coil furnishing the field-magnet excitation, modifying coils
in series in the mains controlling a magnetic shunt in the transformer, and resistances
for regulating the effect of the coils.
Dated thin 02-1 daw at ML 1007
HASELTINE, LAKE & Co.,
45 Southampton Buildings, London, W.C., Agents for the Applicant.