Improvements in Asynchronous Electrical Machines.
Year: 1895

page_text: Date of Application, 16th Aug., 1895
Complete Specification Left, 7th Arr., 1896-Accepted, 23rd May, 1896
[Communicated from abroad by LA SOCIÉTÉ ANONYME POUR LA TRANSMISSION
DE LA FORCE PAR L'ELECTRICITÉ, of 13 Rue Lafayette, Paris, France.]
Improvements in Asynchronous Electrical Machines.
I, CHARLES DENTON ABEL, of No. 28 Southampton Buildings, in the
County of London, Consulting Engineer and Chartered Patent Agent, do
hereby declare the nature of this invention to be as follows:-
The main defect of asynchronous electrical machines, (such as machines in which
the speed of rotation of the moveable part is not synchronous with the frequency
of the alternating currents) whether employed as current generators or as motors,
is due to their mode of excitation. This must be effected by means of alternating
currents, and in order to effect their passage, it is necessary to develop an apparent
amount of werk considerably greater than the actual work, equivalent to the
generation of heat determined by their passage. If this apparent work has to be
supplied. by a current generator, its coefficient of useful effect is considerably
diminished.
If it is to be supplied by a special exciting machine connected to cach dynamo
such for example as a synchronous motor, the armature of which is in a shunt circuit
between the terminal posts of the armature of the dynamo, it will be found that this
exciter requires to be of dimensions comparable with the size of the dynamo to
which it is attached.
If the current is to be supplied by a battery of condensers it will be found that
the cost will be such as to render its use prohibitory.
In all the said cases the ampère-turns necessary for generating the fluxes which
are required to pass through the magnetic circuits of the dynamo are furnished by
its armature, that is to say, by that circuit of the machine which is connected
between the main conductors. If the frequency of the currents supplied by the
main circuit or by the dynamo be designated by 1/T, the frequency of the
variations of the flux in its armature will also be equal to 1/T, and these fluxes
must themselves be generated by currents of the frequency 1/T.
Now, the relation of the apparent work to the actual work necessary for causing
a current of determined intensity to pass through a determined circuit increases
rapidly with the frequency of this current and the frequency 1/T is always great
in practice.
But the course which the fluxes follow in an asynchronous dynamo passes as well
through its induced circuits as through its armature. It matters little for the
developement of these fluxes whether the necessary magnetising force be developed
by ampère turns supplied by its armature or by its induced circuits.
It is known that if the number of the poles of an asynchronous motor be
designated by 2n, and by w the speed of rotation, the frequency of the variations,
of the flux passing through the induced circuits will no longer be 1/T but
n 10,
and that when a similar dynamo is under the normal conditions of working the
frequency
1
T
-
'n 10 is about 50 times smaller than the frequency 1/T.
20)
It results from this that if there be passed into the induced circuits of a
DS1

page_text: asynchronous dynamo and not into its armature, the currents necessary for its
excitation, the relation of the apparent work to the actual work necessary for
effecting the passage of the desired currents will be very near unity as these
currents will always have a very low frequency.
If such a result were obtained and if the necessary exciting currents could be
furnished by an exciting machine the dimensions of which were simply proportional
to the apparent amount of work to be supplied and independent of the frequency of
the currents which it has to generate, the exciting apparatus suitable to be combined
with an asynchronous dynamo, operating either as generator or as motor, for
establishing the equality between the apparent work and the actual work of the
currents passing through its armature, would not be of greater relative
importance than the exciting apparatus with continuous current which is
required to be combined with any synchronous dynamo.
The present invention has for its object to solve the above problem, and consists
in the employment of the following method and means for carrying it out.
In order that the induced circuits of an asynchronous dynamo may generate the
fluxes necessary for its excitement, it is necessary, and it suffices, that they should
be capable of developing a rotary field of suitable intensity having a speed of
rotation relatively to these induced circuits equal to ½-½ (+-).
n
In effect, the relative speed of rotation of the induced circuits relatively to the
armature being equal to w, the speed of the rotary field relatively to the armature
will be equal to the algebraic sum of the two speeds above considered, that is
11 = a sin 2 π
- n 20 t and
T
J₁ =
= a cos 2 π
(nb) t, the intensity a having a value-
G
sufficiently great to determine the developement of the desired fluxes.
Let and designate respectively the resistance and the coefficient of self
induction of each of these induced circuits; the principle of this invention consists
in rendering artificially very nearly zero these two quantities.
If such a result were obtained it would suffice to cause a very small electro-
motive force to act upon these circuits, for determining therein the passage of
currents of the intensity I, and 12. In effect, in designating by the maximum
value of this electro-motive force we have :-

page_text: in generating it by the inductive action of the armature upon the induced circuits,
as the armature only requires for the purpose to generate a flux of negligable
intensity the apparent work which it is necessary to provide at the terminals for
developing this flux will also be negligable.
But the intensity of the exciting current of the armature can be separated into
two components. One of these will have its variations of the same phase as those
of the electro-motive force developed between the terminal posts of the armature.
This portion of the current will absorb a quantity of energy equivalent to the
quantity of heat produced in the induced circuits. Its existence will simply have
the effect of increasing the supply current absorbed by the dynamo if it serves as
motor or of diminishing the supply current furnished by it, if it serves
generator. As it is absolutely necessary to furnish in some manner this quantity
of energy, there will be no cause to diminish artificially the resistance which could
only be done by expending work in some manner.
as
The other component of the exciting current will have its variations shifted by
4th period relatively to those of the electro-motive force maintained between the
terminal posts of the armature. If it is to be reduced to zero, it is necessary to
artificially reduce to zero, the co-efficient of self induction of each of the induced
circnits of the dynamo.
The following conclusion is thus arrived at:
The apparent work available at the terminal posts of an asynchronous dynamo
employed as motor will be equal to the actual work consumed thereby, and the
intensity of the exciting current required to be supplied to its armature, when it
is employed as generator will be zero, if in these two cases, the co-efficient of
self induction of each of its induced circuits is rendered zero artificially.
It has already been proposed for this purpose to close the induced circuits
upon condensers, but this arrangement does not allow of advantage being taken
of the great diminution of the apparent work necessary for effecting the passage
of the exciting currents. In effect, the frequency of these currents is diminished
in the same proportion and all things being otherwise equal, the dimensions of
a condenser capable of supplying a determined amount of apparent work, are
inversely proportional to the frequency of the currents which have to pass through
it. It would not be possible in this case to replace the action of a condenser by
that of a synchronous motor. This would have to supply practically currents the
frequency of which be included between 1 and 2 such a motor would be very
disadvantageously applied.
My correspondents have therefore endeavoured to produce an apparatus which
while being capable of developing the same electromotive forces as a condenser
shall be of dimensions which for a given amount of apparent work to be effected,
shall be independent of the frequency of the currents.
Now assuming the existence of a continuous current machine the armature of
which has a negligable co-efficient of self induction and the inducing part of which
is excited by an alternating current, the electromotive force developed between
the brushes by its rotation will have the same frequency as the inducing current.
Its effective size will only depend upon the mode of construction of the machine,
the speed of rotation, and the effectual intensity of the inducing current; it will
be independent of the frequency of this current. The dimensions of such a
machine for supplying a determined amount of apparent work will therefore be
independent of the frequency of the currents which pass through it and will be
small if this work is sinall.
It will suffice therefore, in order to arrive at the desired result, to close each of
the induced circuits of an asynchronous alternating current machine upon the
armature of a similar machine and to suitably excite its inducing parts. I will
explain by means of an example how this latter function can be naturally fulfilled.
At Fig. 1 of the accompanying drawings is shewn an asynchronous alternating
current machine with single phase currents; A A is the armature, assumed to be
rotatable.

page_text: single encult formed
on the axis and shewn at C.
its several DoDDINз 13, connected to two rings fixed
Two fixed brushes shewn at B bear upon these rings and serve to collect the
current supplied by the armature if the machine serves as current generator, or
serve to convey the necessary current to the armature if the machine acts as receiver
or motor.
The induced circuits are fixed; they are assumed, by way of example to be two
in number, and for facility of expression I will call them the sine circuit and the
cosine circuit.
The bobbins constituting the sine and cosine circuits are regularly crossed as
shewn at Fig. 1. Moreover, the bobbins of each circuit are so wound as to develop
at the same time alternately positive and negative poles as also shewn at Fig. 1,
where the bobbins of the sine circuit are designated by s, and those of the cosine
circuit by the letter c, and where the letters s and c are accompanied by the
signs + and
designating the signs of the poles which these bobbins develop at a
-
certain moment.
At Figs. 2 and 3 are shewn respectively in front view and sectional side view
the exciting machine which is combined with the above mentioned alternate
current machine.
It consists of two continuous current machines having special arrangements but
identical in construction.
Their armatures are fixed on one and the same shaft as shewn at Fig. 3, and
are driven by the same transmission gear.
It is assumed by way of example:
1. That the armatures of these machines are constructed as an ordinary Gramme
ring a a shewn in elevation at Fig. 2 and in section at .Fig. 3.
These rings are provided with collectors oo on which bear diametrically opposite
brushes, bb.
2. That the inducing parts are also formed of rings M M of the Gramme kind,
concentric with the armatures and covered with two distinct windings. The one
half of the sections of the ring M M is shewn in section at Fig. 2 so as to shew
the two bobbins constituting each section.
Each series of bobbins is grouped together in the ordinary manner. The
ring M M is thus covered by two distinct windings of the Gramine kind. One of
these windings serves to generate the inducing flux.
For this purpose the points of entrance and issue of the currents follow a line
forming an angle of 90° with the line of contact of the brushes as shewn in the
diagram Fig. 4.
The points of entrance and issue of the circuit formed by the second winding, on
the other hand are in the line of the brushes, as shown.
The circuit thus constituted should have exactly the same number of coils as
the armature and is mounted in series therewith. This mounting is effected in
such a manner that the poles developed thereby along the line of the brushes shall
be in opposition to those developed by the armature. The latter can then not
develop any flux and will behave as if its coefficient of self induction were nul.
The diagram shewn at Fig. 5 will explain the manner in which the induced
circuits of the alternate current machine and the several circuits of the exciting
machine are grouped together. The sine circuit of the alternating machine shewn
by the letter S, is connected in series with the inducing circuit Ic of one of the
dynamos of the exciting machine, and the armature As of the other dynamo. It
includes at the same time the circuit Js serving to render nul the coefficient of
apparent self induction of the armature As.
The cosine circuit of the alternating machine, represented by the letter C, is
connected in series with the inducing circuit Is of one of the dynamos of the
exciting machine, and the armature Ac of the other dynamo.
C
It includes also the circuit Jc serving to render nul the coefficient of apparent
self induction of the armature A c. Under these conditions the alternate current

page_text: machine will develop in these two induced circuits currents shifted th period,
which I will call sine and cosine currents, it will be seen therefore that the
armature of the exciting machine which is traversed by the sine current, will be
excited by the cosine current, and conversely.
On the other hand the two currents, sine and cosine have the same useful
intensity.
It results from this that the electro motive forces developed by the exciting
machine in each of the induced circuits are proportional to the useful intensities of
the currents which pass through them, and are shifted th period relatively to
these intensities:
By suitably arranging the direction of the inducing winding Ic and I s, I can
arrange so that these electromotive forces shall be in advance of the intensities.
Under these conditions these electromotive forces will be identical with those
which the introduction of condensers of the same capacity in the two induced
circuits would produce. The desired result is therefore obtained.
In the above description it was assumed that the machine was one with single
phase currents. But all that has been said is independent of the mode of con-
stituting the armature of this alternate current machine, and applies equally to the
case where such armature produces or consumes polyphase currents.
The armature A A for single phase currents shewn in Fig. 1 may therefore be
replaced by an armature for polyphase currents.
It has been also assumed that the alternate current machine is provided with
two induced circuits. This number can also be varied, but it is necessary to
employ as many distinct exciting dynamos as there are distinct circuits on the
induced part.
I will assume for example that there are three induced circuits.
These must be traversed respectively by currents of the intensity :
It is necessary for solving the problem, that the exciting dynamo of which the
armature is traversed by the current of the intensity:
= a sin 2 π
and is excited by a current of the intensity: 4₁ = a cos. 2 π
Although such a current is not available, there being two currents:
nwt,
T
(π- n w) o
G
- n wo
T
20) t.
= a Bin
2 πT
-
(( − n w)t + }) and ja
= a sin 2 T
(-
-
nw)t + the same result can
be readily obtained.
If N be the number of coils of each bobbin of the inducing circuit that is to be
traversed by the current of the intensity: ₁ = a cos 2 πT
2 = (³½³
G
T- nw)t,
we can
replace each of these bobbins by two others, superposed, having respectively n
and
ng coils, and which are traversed by currents of the intensity j, and j, which
are of course available.
The total magnetising force developed by these two bobbins will be equivalent to
the magnetising force developed by the single bobbin with N superposed coils,
traversed by the current of the intensity if:

page_text: It will thus be seen that it will be possible to cause each of the exciting dynamos
to develop an electromotive force shifted th period relatively to the intensity of
the current which traverses its armature.
Au analogous proceeding would be employed if the number of the induced
circuits of the asynchronous dynamo were greater than three.
But it must be observed that as it suffices in all cases to employ two induced
circuits, it would be a useless complication to increase their number.
It will be readily seen that it is possible to transform an asynchronous dynamo
with its exciting machine as described above, into a synchronous dynamo. It
suffices for this purpose to modify the mode of coupling up the several circuits
of the exciting machine in the manner shewn at Fig. 6. With this mode of
grouping, each of the armatures of the exciting machine will be connected in series
with its own inducing part. It will thus be transformed into an ordinary
continuous current dynamo, and the inducing parts of the machine will be excited
by continuous currents.
Dated this 16th day of August. 1895
ABEL & IMRAY,
Agents for the Applicant.
COMPLETE SPECIFICATION.
Improvements in Asynchronous Electrical Machines.
1, CHARLES DENTON ABEL, of No. 28, Southampton Buildings, in the
County of London, Consulting Engineer and Chartered Patent Agent, 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 main defect of asynchronous electrical machines (such as machines in which 3
the speed of rotation of the moveable part is not synchronous with the frequency

page_text: of the alternating currents) whether employed as current generators or as motors,.
is due to their mode of excitation.
This must be effected by means of alternating currents, and in order to effect
their passage, it is necessary to develop an apparent amount of work considerably
greater than the actual work, equivalent to the generation of heat determined by
their passage.
If this apparent work has to be supplied by a current generator,.
its co-efficient of useful effect is considerably diminished.
If it is to be supplied by a special exciting machine connected to each dynamo,.
such for example as a synchronous motor, the armature of which is in a shunt
circuit between the terminal posts of the armature of the dynamo, it will be found
that this exciter requires to be of dimensions comparable with the size of the
dynamo to which it is attached.
If the current is to be supplied by a battery of condensers it will be found that.
the cost will be such as to render its use prohibitory.
In all the said cases the ampère-turns necessary for generating the fluxes which.
are required to pass through the magnetic circuits of the dynamo are furnished by
its armature, that is to say, by that circuit of the machine which is connected
between the main conductors. If the frequency of the currents supplied by the
main circuit or by the dynamo be designated by 1/T, the frequency of the variations.
of the flux in its armature will also be equal to 1/T, and these fluxes must
themselves be generated by currents of the frequency 1/T.
Now, the relation of the apparent work to the actual work necessary for causing
a current of determined intensity to pass through a determined circuit increases.
rapidly with the frequency of this current and the frequency 1/T is always great
in practice.
But the course which the fluxes follow in an asynchronous dynamo passes as well
through its induced circuits as through its armature. It matters little for the
developement of these fluxes whether the necessary magnetising force be developed
by ampère turns supplied by its armature or by its induced circuits.
It is known that if the number of the poles of an asynchronous motor be
designated by 2n, and by w the speed of rotation, the frequency of the variations,.
1
T
n 10.
of the flux passing through the induced circuits will no longer be I/T but
and that when a similar dynamo is under the normal conditions of working the
frequency (✗--- nw) is about 50 times smaller than the frequency 1/T.
It results from this that if there be passed into the induced circuits of an
asynchronous dynamo and not into its armature, the currents necessary for its
excitation, the relation of the apparent work to the actual work necessary for
effecting the passage of the desired currents will be very near unity as these currents
will always have a very low frequency.
If such a result were obtained and if the necessary exciting currents could be
furnished by an exciting machine the dimensions of which were simply proportional
to the apparent amount of work to be supplied and independent of the frequency
of the currents which it has to generate, the exciting apparatus suitable to be
combined with an asynchronous dynamo, operating either as generator or as motor,
for establishing the equality between the apparent work and the actual work of
the currents passing through its armature, would not be of greater relative
importance than the exciting apparatus with continuous current which is required
to be combined with any synchronous dynamo.
The present invention has for its object to solve the above problem, and
consists in the employment of the following method and means for carrying
it out.
In order that the induced circuits of an asynchronous dynamo may generate the
fluxes necessary for its excitement, it is necessary, and it suffices, that they should

page_text: This electromotive force being rendered almost nul, there will be no inconvenience
in generating it by the inductive action of the armature upon the induced circuits,
as the armature only requires for the purpose to generate a flux of negligable
intensity, the apparent work which it is necessary to provide at the terminals for
developing this flux will also be negligable.
But the intensity of the exciting current of the armature can be separated into
two components. One of these will have its variations of the same phase as those
of the electro-motive force developed between the terminal posts of the armature.
This portion of the current will absorb a quantity of energy equivalent to the
quantity of heat produced in the induced circuits. Its existence will simply have
the effect of increasing the supply current absorbed by the dynamo if it serves as
motor or of diminishing the supply current furnished by it if it serves as generator.
As it is absolutely necessary to furnish in some manner this quantity of energy,
there will be no cause to diminish artificially the resistance r which could only be
done by expending work in some manner.
The other component of the exciting current will have its variations shifted
by th period relatively to those of the electromotive force maintained between
the terminal posts of the armature. If it is to be reduced to zero, it is necessary

page_text: to artificially reduce to zero, the co-efficient of self induction of each of the
induced circuits of the dynamo.
The following conclusion is thus arrived at:
The apparent work available at the terminal posts of an asynchronous dynamo
employed as motor will be equal to the actual work consumed thereby, and the
intensity of the exciting current required to be supplied to its armature, when it
is employed as generator will be zero, if in these two cases, the co-efficient of self
induction of each of its induced circuits is rendered zero artificially.
It bas already been proposed for this purpose to close the induced circuits upon
condensers, but this arrangement does not allow of advantage being taken of the
great diminution of the apparent work necessary for effecting the passage of the
exciting currents. In effect, the frequency of these currents is diminished in
the same proportion and all things being otherwise equal, the dimensions of a
condenser capable of supplying a determined amount of apparent work, are inversely
proportional to the frequency of the currents which have to pass through it. It
would not be possible in this case to replace the action of a condenser by that of
a synchronous motor. This would have to supply practically currents the
frequency of which would be included between 1 and 2, such a motor would be
very disadvantageously applied.
My correspondents have therefore endeavoured to produce an apparatus which
while being capable of developing the same electro motive forces as a condenser
shall be of dimensions which for a given amount of apparent work to be effected,
shall be independent of the frequency of the currents.
Now assuming the existence of a continuous current machine, the armature of
which has a negligable co-efficient of self induction and the inducing part of which
is excited by an alternating current, the electromotive force developed between
the brushes by its rotation will have the same frequency as the inducing current.
Its effective size will only depend upon the mode of construction of the machine,
the speed of rotation, and the effectual intensity of the inducing current; it will
be independent of the frequency of this current. The dimensions of such a
machine for supplying a determined amount of apparent work will therefore be
independent of the frequency of the currents which pass through it and will be
small if this work is small.
It will suffice therefore, in order to arrive at the desired result, to close each of
the induced circuits of an asynchronous alternating current machine upon the
armature of a similar machine and to suitably excite its inducing parts, I
will explain by means of an example how this latter function can be naturally
fulfilled.
'
At Figure 1 of the drawings accompanying my Provisional Specification is
shewn an asynchronous alternating current machine with single phase currents;
A A is the armature, assumed to be rotatable.
The single circuit formed by its several bobbins is connected to two rings fixed
on the axis and shewn at C.
Two fixed brushes shewn at B bear upon these rings and serve to collect the
current supplied by the armature if the machine serves as current generator, or
serve to convey the necessary current to the armature if the machine acts as
receiver or motor.
The induced circuits are fixed; they are assumed by way of example to be two
in number, and for facility of expression I will call them the sine circuit and the
cosine circuit.
The bobbins constituting the sine and cosine circuits are regularly crossed as
shewn at Figure 1. Moreover, the bobbins of each circuit are so wound as to
develop at the same time alternately positive and negative poles as also shewn at
Figure 1, where the bobbins of the sine circuit are designated by s, and those of
the cosine circuit by the letter c, and where the letters & and c are accompanied by
the signs and designating the signs of the poles which these bobbins develop
at a certain moment.
-
8

page_text: At Figures 2 and 3 are shewn respectively in front view and sectional side view
the exciting machine which is combined with the above mentioned alternate
current machine.
It consists of two continuous current machines having special arrangements but
identical in construction.
Their armatures are fixed on one and the same shaft as shewn at Figure 3, and
are driven by the same transmission gear.
It is assumed by way of example
==
1. That the armatures of these machines are constructed as an ordinary
Gramme ring a a shewn in elevation at Figure 2 and in section at Figure 3.
These rings are provided with collectors o o on which bear diametrically opposite
brushes bb.
2. That the inducing parts are also formed of rings M M of the Gramme kind,
concentric with the armatures and covered with two distinct windings. The one
half of the sections of the ring M M is shewn in section at Figure 2 so as to shew
the two bobbins constituting each section.
Each series of bobbins is grouped together in the ordinary manner. The
ring M M is thus covered by two distinct windings of the Gramme kind. One
of these windings serves to generate the inducing flux.
For this purpose the points of entrance and issue of the currents follow a line
forming an angle of 90° with the line of contact of the brushes as shewn in the
diagram Figure 4.
The points of entrance and issue of the circuit formed by the second winding, on
the other hand are in the line of the brushes as shewn.
The circuit thus constituted should have exactly the same number of coils as the
armature and is mounted in series therewith. This mounting is effected in such a
manner that the poles developed thereby along the line of the brushes shall be in
opposition to those developed by the armature. The latter can then not develop
any flux and will behave as if its coefficient of self induction were nul.
The diagram shewn at Figure 5 will explain the manner in which the induced
circuits of the alternate current machine and the several circuits of the exciting
machine are grouped together. The sine circuit of the alternating machine
shewn by the letter S, is connected in series with the inducing circuit I c of one of
the dynamos of the exciting machine, and the armature As of the other dynamo.
It includes at the same time the circuit Js serving to render nul the coefficient of
apparent self induction of the armature As.
'
The cosine circuit of the alternating machine, represented by the letter C, is
connected in series with the inducing circuit Is of one of the dynamos of the
exciting machine, and the armature Ac of the other dynamo.
It includes also the circuit Jc serving to render nul the coefficient of apparent
self induction of the armature A c. Under these conditions the alternate current
machine will develop in these two induced circuits currents shifted th period, which
I will call sine and cosine currents, it will be seen therefore that the armature of
the exciting machine which is traversed by the sine current, will be excited by the
cosine current, and conversely.
On the other hand the two currents, sine and cosine have the same useful
intensity.
It results from this that the electro motive forces developed by the exciting
machine in each of the induced circuits are proportional to the useful intensities
of the currents which pass through them, and are shifted tth period relatively to
these intensities.
By suitably arranging the direction of the inducing winding Ic and I s. I can
arrange so that these electro-motive forces shall be in advance of the intensities:
Under these conditions, these electro motive forces will be identical with those
which the introduction of condensers of the same capacity in the two induced
circuits would produce: The desired result is therefore obtained.
In the above description it was assumed that the machine was one with single
"

page_text: phase currents. But all that has been said is independent of the mode of
constituting the armature of this alternate current machine, and applies equally to
the case where such armature produces or consumes polyphase currents.
The armature A A for single phase currents shewn in Figure 1 may therefore
be replaced by an armature for polyphase currents.
It has been also assumed that the alternate current machine is provided with.
two induced circuits. This number can also be varied but it is necessary to
employ as many distinct exciting dynamos as there are distinct circuits on the
induced part.
I will assume for example, that there are three induced circuits.
These must be traversed respectively by currents of the intensity

page_text: It will thus be seen that it will be possible to cause each of the exciting dynamos
to develop an electro-motive force shifted 4th period relatively to the intensity of
the current which traverses its armature.
An analogous proceeding would be employed if the number of the induced
circuits of the asynchronous dynamo were greater than three.
But it must be observed that as it suffices in all cases to employ two induced
circuits it would be a useless complication to increase their number.
It will be readily seen that it it is possible to transform an asynchronous dynamo
with its exciting machine as described above, into a synchronous dynamo. It
suffices for this purpose, to modify the mode of coupling up the several circuits of
the exciting machine in the manner shewn at Figure 6. With this mode of
grouping each of the armatures of the exciting machine will be connected in
series with its own inducing part. It will thus be transformed into an ordinary
continuous current dynamo, and the inducing parts of the machine will be excited
by continuous currents.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. An asynchronous poly-phase or single-phase alternate current electrical
machine that can serve either as generator, or as motor, wherein the intensity of
the exciting currents which have to be supplied to the several circuits of its
armature by one or more external sources of electrical energy is rendered
practically zero, by artificially making zero the apparent self induction of each of
the short circuited induced circuits of the machine substantially as described.
2. The method of rendering zero the co-efficient of apparent self induction of
one of the induced circuits of an asynchronous alternate current machine, which
consists in closing this circuit on the armature of a machine of the Gramme kind
with collector, the inductor of which is excited by currents supplied by the other
induced circuit or circuits of the said asynchronous machine in such manner that
the alternating electro-motive force developed in the armature of this machine
shall have its phases shifted one quarter of a period relatively to those of the
current which passes through it, substantially as described.
3. The herein described special construction of asynchronous alternate current
electrical machines for carrying out the methods of operating referred to in the
preceding claims.
A 1906
ABEL & IMRAY,
Agents for the Applicant.