Improvements in Apparatus for Transforming Continuous Electrio Currents into Alternating Currents.
Year: 1895

page_text: Date of Application, 13th Nov., 1895
Complete Specification Left, 11th July. 1896-Accepted, 15th Aug., 1896
PROVISIONAL SPECIFICATION.
[Communicated from abroad by LA SOCIÉTÉ ANONYME POUR LA TRANSMISSION
DE LA FORCE PAR L'ELECTRICITÉ, of 13 Rue Lafayette, Paris, France.].
Improvements in Apparatus for Transforming Continuous Electrio
Currents into Alternating Currents.
I, CHARLES DENTON ABEL, of No. 28 Southampton Buildings, Chancery
Lane, in the County of London, Consulting Engineer and Chartered. Patent
Agent, do hereby declare the nature of this invention to be as follows:-
In the Specification to Patent No. 17826 of 1892 was described the theory and
construction of an apparatus by means of which single or polyphase alternating
currents were converted into a continuous current, and vice versa.
The present invention relates to an improved construction of such a transformer
for the case where it is required to transform a continuous current into alternating
currents, whereby all sparking at the bruslies is avoided, in destroying the effects
of self induction.
I will briefly restate the main features of the above named apparatus of Patent
No. 17826 of 1892. Assuming that it be required to produce a three-phase
current, for example, the transformer has in this case three magnetic cores closed
in themselves, each core has a winding serving to receive the three phase current
obtained by the sinoidal variation of the fluxes in the cores, which variation results
from the action of a second winding on the cores, through which passes the current
which is to be transformed. The elementary bobbins of this winding are so
arranged as regard the number of convolutions of each hobbin and the direction
thereof, that the number of ampère turns due to the passage of the continuous
current varies according to a sinoidal law. The continuous current to be trans-
formed is, distributed to the second above named set of windings by means of
brushes bearing on revolving contact rings communicating respectively with the
plates of a revolving collector on the same shaft as the rings, which plates com-
imunicate by means of brushes with the circuit of the source of the continuous
current, the said shaft being driven by a suitable motor.
According to the improved arrangement which forms the subject of the present
invention there is mounted between the said contact rings and brushes, a small
synchronous motor of the following construction and arrangement.
Upon, a fixed annular core formed of superposed and insulated iron plates is
formed a winding similar to a gramme ring, which winding is divided into as
many elementary bobbins as there are brushes on the before mentioned collector.;
these bobbins are connected respectively to the brushes bearing on the contact
rings. The gramme ring will consequently produce a rotary field when it is
passed through by currents regularly shifted by the collector brushes. Within the
gramme ring is mounted an inductor formed of two polar pieces connected by a
transverse bar on which are coiled two circuits. The coiling of each circuit is so
formed as to produce poles of opposite sign in each polar piece as the coils aro
passed through by the continuous current. The terminals of the two circuits are
in communication with brushes bearing on four rings. The one circuit, being of

page_text: thick wire, is mounted in series with the circuit with continuous current which
supplies the before mentioned brushes bearing on the collector.
The other of the two circuits is of thin wire and is mounted in shuut between
the said brushes.
The said inductor is provided with a deadening circuit formed by two side
cheeks of conducting non-magnetic metal connected together by transverse rods, of
the same nature passing through a laminated iron ring, this circuit being arranged
to have the smallest possible electrical resistance.
The inductor will revolve synchronously with the first named shaft carrying the
contact rings and collectors, and if the coilings have been suitably determined, its
rotation will cause the production in the before mentioned gramme ring of currents
which circulate through the circuits of the transformer connected between the
consecutive plates of the collector.
Under these conditions all production of sparking at the brushes will be avoided.
Instead of constructing the inductor of the motor with only two polar pieces, it
may have 2 poles, with 2 n series of windings ou the gramme ring, and so
arranged as to produce as many circuits regularly arranged round the ring as there
are plates on the collector.
It will be evident that the inductor may be made the fixed part of the motor and
the gramme ring the rotating part, in which case the shifted currents would be
supplied through revolving contact rings and brushes.
Dated this 13th day of November 1895.
ABEL & IMRAY,
Agents for the Applicant.
Improvements in Apparatus for Transforming Continuous Electric
Currents into Alternating Currents.
1, CHARLES DENTON ABEL, of No. 28 Southampton Buildings, Chancery
Lane, in the County of London, Consulting Engineer and Chartered Patent
Agent, do horeby 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:―
In the Specification to Patent No. 17826 of 1892 was described the theory and
construction of an apparatus by means of which single or polyphase alternating
currents were converted into a continuous current, and vice versa.
The present invention relates to an improved construction of such a transformer
for the case where it is required to transform a continuous current into alternating
'currents, whereby all sparking at the brushes is avoided, in destroying the effects
of self induction.
I will briefly restate the main features of the above named apparatus of Patent
No. 17826 of 1892. Assuming that it be required to produce a three-phase
current, for example, the transformer has in this case three magnetic cores closed
in themselves, each core has a winding serving to receive the three phase current
obtained by the sinusoidal variation of the fluxes in the cores which variation
results from the action of a second winding on the cores, through which passes the
current which is to be transformed. The elementary bobbins of this winding are
so arranged as regards the number of convolutions of each bobbin and the direction
thereof, that the number of ampère turns due to the passage of the continuous
current varies according to a sinusiodal law. The continuous current to be trans-
formed is distributed to the second above named set of windings by means of
brushes bearing on revolving contact rings communicating respectively with the

page_text: plates of a revolving collector on the same shaft as the rings, which plates
communicate by means of brushes with the circuit of the source of the continuous
current, the said shaft being driven by a suitable motor.
According to the improved arrangement which forms the subject of the present
invention as shewn in side view Fig. 1 and in transverse section Fig. 2 of the
accompanying drawings there is mounted between the said contact rings, and
brushes &c. a small synchronous motor of the following construction and
arrangement.
Upon a fixed annular corek formed of superposed and insulated iron plates is
formed a winding similar to a gramme ring, which winding is divided into as many
elementary bobbins as there are plates on the collector L; these bobbins are
connected respectively to the brushes f¹ƒ³ &c.
The ring & will consequently produce a rotary field when it is traversed by the
regularly shifted currents from the collector brushes. Within the gramme ring
is mounted an inductor I formed of two polar pieces M. N connected by a trans-
verse core on which are coiled two circuits. The coiling of each circuit is such as
to produce poles of opposite sign-in the polar pieces M. N. as the coils are
traversed by the continuous current. The terminals of the two circuits are in
communication with brushes bearing on four rings d' d' d' d. The one circuit, of
thick wire, is mounted in series with the circuit of continuous current which
supplies the brushes 2 &c. It communicates at A and B with conductors
leading respectively to Fi and S.
The other of the two circuits is of thin wire in shunt between the said bushes,
communicating with their conductors at G and D. The inductor I is provided with
a deadening circuit formed by two side cheeks E of conducting non-inagnetic metal
connected together by transverse bolts of the same nature passing through a
laminated iron ring, this circuit being arranged to have the smallest possible electrical
resistance.
The inductor I will revolve synchronously with the shaft 001 carrying the
contact rings and collectors, and, if the coilings have been suitably determined, its
rotation will produce in the gramme ring & currents which circulate through the
circuits of the transformer connected between the consecutive plates of the
collector. Under these conditions all production of sparking at the brushes will be
avoided.
Instead of constructing the inductor of the motor with only two polar pieces,
it may have 2 n poles, with 2 n series of windings on the gramme ring, and so
arranged as to produce as many circuits regularly arranged round the ring as there
are plates on the collector L.
It will be evident that the inductor may be made the fixed part of the motor
and the gramme ring the rotating part, in which case the shifted currents would
be supplied through revolving contact rings and brushes.
The same result might be obtained by mounting the ring between the
wires a, y, z so that it would have three circuits or 3 series of 2 n circuits
according as the armature of the synchronous motor had 2 or 2 n poles.
The action of the arrangements described may be thus explained.
=
If between the extremities of a circuit having self induction there be maintained
an alternating electromotive force such that h=h, sin 2 wt, the intensity traversing
this circuit will have an expression of the form i: asin2πωι + a cos 2πω,in which
a and a indicate two constants. The current of intensity may therefore be
considered as the source of two currents, the one having the intensity a sin 2 wt
will have its variations of the same phase with the electromotive force and may
be termed "watted," the other having the intensity a cos 2 wt will have its
variations shifted wave from those of the electromotive force and may be termed
"dewatted."
The intensity of the watted current ceases with that of the electromotive
force h, at which moment the intensity of the dewatted current is at its inaximum.

page_text: If a circuit is branched between two plates of a collector, its electromotive force
becomes nil when the plates are short circuited by the brushes.
If only watted currents traverse this circuit their intensity becomes nil at the
moment when the brushes pass from one plate to the next which they thus do
without interrupting a current and consequently without causing sparks.
On the other hand if a dewatted current traverses the circuit, this is at its
maximum when the brushes pass from one plate to the next, consequently, the
current being thus interrupted there must be sparking. As in a self induction
circuit there are such dewatted currents there would be sparking in the apparatus
described but for the precautions set forth, by providing in shunt between the
plates of the collector other circuits which have always to be traversed by dewatted
currents equal but of contrary sign. to those which traverse the circuits of the
transformer.
It requires only to develope suitable electromotive forces in these new circuits
which are those of the armature of the synchronous motor, the currents having the
desired frequency when the motor revolves synchronously.
If the motor revolved in vacuo having no work to perform the currents traversing
the armature would have their intensities shifted wave relatively to the electro-
motive forces maintained between the ends of the armature circuits, and the direction
of these currents would vary according as their passage would increase or diminish
the flux caused by the inductor so as to bring it up to a value corresponding
exactly with the electromotive forces maintained between the ends of the armature
circuits.
It is therefore only necessary to arrange. suitably the existing force of the
syuchronous motor. As generally the intensity of the dewatted currents furnished
by this motor should vary with that of the currents absorbed by the transformer,
the inductor of the motor is wound compound, the first winding being in shunt
between the brushes of the collector, the second in series with the circuit supplying
the continuous current.
Having now particularly described and ascertained the nature of this inven
tion and in what manner the same is to be performed; I declare that what I
claim is :-
:-
Apparatus for transforming continuous currents of any tension into alternating
currents of any tension, consisting of a transformer of the kind described in the
Specification No. 17826 of 1892 having mounted between the different sections of
its sinusoidal winding, an armature forming part of a synchronous motor the
inductor whereof has two windings the one traversed by the continuous current to
be transformed, the other connected in shunt between the brushes of the collector
for the transformer.
Dated thin 11th T... 1000
ABEL & IMRAY,
Agents for the Applicant.