Improved Construction of Asynchronous Motor for Single or Polyphase Alternating Electrical Currents in Combination with an Auxiliary Synchronous Motor
Year: 1897

page_text: Date of Application, 2nd Mar., 1897
• Complete Specification Left, 17th Nov., 1897-Accepted, 24th Dec., 1897
FRUVIDIONAL DI EUIT IQATION.
"Improved Construction of Asynchronous Motor for Single or
Polyphase Alternating Electrical Currents in Combination with
an Auxiliary Synchronous Motor."
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 (as communicated to me from abroad by
La Société Anonyme pour la transmission de la force par L'electricite, of 13 Rue
Lafayette, Paris, France,) to be as follows:-
Asynchronous motors for single or polyphase alternating. currents have the
disadvantage of requiring to be supplied with an amount of energy greatly exceeding
that which they actually consume. The motors working with single phase currents
have in addition the disadvantage that they can only be started by the employment
of special means, and that they cannot be so started under a load without requiring
from the supply circuit an excessive amount of energy.
The present invention has for its object to obviate these disadvantages.
For this purpose, assuming for simplicity's sake a bi polar single phase motor, this
consists according to the present invention of a revolving inducing part branched
between the leads of the supply circuit and which has two identical diametrical
opposite coils constituting a single circuit which receives the current from the supply
circuit by means of contact rings and brushes. These coils are so grouped that the
entering current developes at each moment on the surface of the field magnets two
diametrically opposite poles of opposite sign. Secondly the motor consists of a fixed
induced part or armature of a ring shape, which has n identical coils or bobbins,
placed at equal angles apart.
2πT
n
With this asynchronous motor is combined an auxiliary asynchronous motor, which
is also assumed to be bi polar, and the armature of which (supposed to be fixed) is
also provided with n identical coils placed at equal angles apart.
2π
n
Designating with C¹ C².... On the n induced coils of the asynchronous motor, and
C5 C. Cn the n coils of the armature of the synchronous motor, the coil C is
closed upon the coil C' by connecting together the two points of entrance of the
coils C¹ and C5, as also their points of exit. In the same way the coil C² is closed on
the coil C, and so on..
The inducer or magnetic field of the synchronous motor, which is assumed to
rotate, includes, firstly, an inducing coil branched between two rings on which bear
two brushes. By their means a continuous current can be passed from any con-
venient source into the said inducing coil. Secondly, it includes an annular
conducting screen formed by a series of copper bars passing transversely through
polar enlargements of the inducer, as close as possible to the air space between this
and the armature such bars being connected at each end to a ring of 'copper or
bronze on the sides of the inducer.

page_text: .
1
.
'
T
The synchronous motor can be considered as fed by a transformer whose primary
circuit is constituted by the inducer of the asynchronous motor while the second
circuit is constituted by the induced circuits of this motor. If we call the fre
quency of the currents that excite the inducer of the asynchronous motor then the
magnetising force developed by this inducer will tend to produce two rotary fields
relatively thereto having a speed the one being in the one direction and the second
in the opposite direction. The coils C³ C° C ..... of the synchronous motor being
mounted in opposition to the corresponding coils C¹ C²..... of the asynchronous
motor, they will necessarily be the seat of equal electromotive forces of contrary sign.
That is to say the synchronous motor will also be the seat of two rotary fields moving
with the speed but in contrary directions, and these fields, cannot attain an
appreciable intensity as they have to pass through the said annular screen of bars of
the inducer. But if by any means the inducer of the synchronous motor be started
with a speed
2, the field turning in the same direction with it will only have
relatively to the screen, while the other will have a speed of
1 + Ω
a speed
T
=====
relatively thereto. The synchronous motor, in consequence of its screen, will assume
a speed very near which allows of its sychronisation by introducing into the in-.
1
ducing coil a continuous current supplied from any source.
The synchronism having been obtained, the screen will have no farther action on
the field which will turn in the same direction, while it will almost entirely prevent
the development of the field rotating in the contrary direction.
But the field produced by the coil of the revolving inducer will be added on to the
existing rotary field, and can increase its action to any desired extent.
The necessary equality between the electromotive forces in the coils C¹C². . .
and C5 Co. mounted in opposition will cause the production in the asynchronous
motor of a single magnetic field turning in the same direction as the synchronous
motor. As the intensity of this field only depends upon the intensity of the field
developed in the synchronous motor, it will increase with the magnetising force of
the inducing coil of the latter without the inducer of the asynchronous motor being
required to furnish dewatted currents for developing this field under these conditions
there will not only be generated in the asynchronous motor a powerful field which
renders it capable of starting under a load, but this field is in reality created by the
continuous current that passes through the inducing coil of the synchronous motor,
so that the intensity of the dewatted currents which the supply circuit has to
furnish to the asynchronous motor can be rendered nul and even negative even at
the moment of starting.
When once the asynchronous motor is started and has acquired a speed of
rotation = 2, a magnetic field which will move with the speed relatively to the
inducer thereof, will-only have a speed of
-
T
-
These will be the seat of currents of the frequency
T
relatively to the induced circuits.
т
0.
The asychronous motor, the speed of rotation of which will always be proportional
to the frequency
, will consequently gradually slacken in speed, and when
T
--
the motor has arrived at its normal speed, the synchronous motor will only revolve
with a very slow speed which in general, if
40, will be between 1 and 2 revo-
T
lutions per second.

page_text: This fact is very important. In effect, the auxiliary synchronous motor will only
have to revolve at a quick speed during the short time of starting the asynchronous
motors. This will enable the auxiliary motor to be made of comparatively small
dimensions relatively to those of the asynchronous motor.
What has been said above relatively to a motor with single phase currents is
equally applicable to a motor with polyphase currents; it is only necessary to replace
the described inducer of the asynchronous motor by one having polyphase circuits.
At the moment of starting the auxiliary synchronous motor. as there is no opposing
electromotive force except the small one due to chemical resistances etc of the several
circuits of the two motors, the current supplied by the line to the inducing circuit of
the asynchronous motor would acquire a very great intensity which would be very
disadvantageous both as regards the motors and the consequent lowering of the voltage
in the supply circuit. This inconvenience is obviated by introducing rheostats with
variable resistances in the several circuits connecting the induced coils of the
asynchronous motor with the armature coils of the synchronous motor, which
resistances would be cut out as soon as the motor was started.
For starting the synchronous motor if this is too large to start it by hand and if the
asynchronous motor has single phase currents, the armature of the former is provided
with two special starting circuits which at the one end are connected together and to
the return lead of the supply circuit, and in the one circuit is included inseries there-
with a self induction coil or a condenser, and in the other is included a resistance
a switch being provided, for changing the connections according as the motor is to
run in the one direction or the other. The other ends of the two circuits are also
connected together and to the contact plate of a switch whereby they can be connected
to the supply lead of the main circuit. When the motor is started the switch is dis-
connected from the starting circuits and is made to establish the connection with the
inducing circuit of the asynchronous motor.
ABEL & IMRAY
Agents for the Applicant.
"Improved Construction of Asynchronous Motor for Single or
Polyphase Alternating Electrical Currents in Combination with
an Auxiliary Synchronous Motor."
I, CHARLES DENTON ABEL, of Birkbeck Bank Chambers, Southampton Buildings,
Chancey Lane, in the County of London, Consulting Engineer and Chartered
Patent Agent, do hereby declare the nature of this invention (which has been
communicated to me from abroad by La Société Anonyme pour la transmission de la
force par l'électricité, of 13 Rue Lafayette, Paris, France), and in what manner the
same is to be performed to be particularly described and ascertained in and by
the following statement:-
Asynchronous motors for single or polyphase alternating currents have the
disadvantage of requiring to be supplied with an amount of energy greatly exceeding
that which they actually consume. The motors working with single phase currents
have in addition the disadvantage that they can only be started by the employment
of special means, and that they cannot be so started under a load without requiring
from the supply circuit an excessive amount of energy.
The present invention has for its object to obviate these disadvantages.
For this purpose, assuming for simplicity's sake a bi-polar single phase motor, as
shewn at M Figure 1 of the accompanying drawings, this consists according to the

page_text: present invention of a revolving inducing part I branched between the leads of the
supply circuit and which has two identical diametrical opposite coils B¹ B² constituting
a single circuit which receives the current from the supply circuit by means of contact
rings 61 62 and brushes f¹ f2. These coils are so grouped that the current entering
through the rings 61 62 developes at each moment on the surface of the field magnets
two diametrically opposite poles of opposite sign. Secondly the motor consists of a
fixed induced part or armature S of a ring shape which has n identical coils or
bobbins, such as C1 C2 C3 C4 . . . . (n:
= 4 on the Figure) placed at equal
supply circuit and which has two identical diametrical opposite coils B¹ B² constituting
a single circuit which receives the current from the supply circuit by means of contact
rings 61 62 and brushes f¹ f2. These coils are so grouped that the current entering
through the rings 61 62 developes at each moment on the surface of the field magnets
two diametrically opposite poles of opposite sign. Secondly the motor consists of a
fixed induced part or armature S of a ring shape which has n identical coils or
bobbins, such as C1 C2 C3 C4.
= 4 on the Figure) placed at equal
angles apart.
"
(n
With this asynchronous motor M is combined an auxiliary synchronous motor N,
which is also assumed to be bi-polar, at Figure 1, and the armature A of which
(supposed to be fixed) is also provided with n identical coils placed at equal
2πT
angles apart.
n
Designating with C¹ C² .... C" the n induced coils of the asynchronous motor M,
and C5 C... C the n coils of the armature of the synchronous motor N, the
coil C¹ is closed upon the coil C5 by connecting together the two points of entrance
of the coils C¹ and C5, as also their points of exit. In the same way the coil C² is
closed on the coil C, and so on, as shown at Figure 2.
The inducer or magnetic field J of the synchronous motor N, which is assumed to
'rotate, includes, firstly, an inducing coil D. branched between two rings 63 64 on
which bear two brushes f³ ft. By their means a continuous current can be passed
when required from any convenient, source into the said inducing coil D.
Secondly, it includes an annular conducting screen E formed by a series of copper
bars passing transversely through polar enlargements of the inducer, as close as
possible to the air space between this and the armature, such bars being connected
at each end to a ring of copper or bronze on the sides of the inducer.
T
The synchronous motor N can be considered as fed by a transformer whose primary
circuit is constituted by the inducer I of the asynchronous motor M while the
secondary circuit is constituted by the induced circuits of this motor. If we call
the frequency of the currents that excite the inducer I of the asynchronous motor
then the magnetising force developed by this inducer will tend to produce two rotary
fields relatively thereto having a speed 1, the one moving in the one direction and
the second in the opposite direction. The coils C5 C6 C7 ... of the synchronous
motor N being mounted in opposition to the corresponding coils C¹ C²..... of the
asynchronous motor M, they will necessarily be the seat of equal electromotive forces
of contrary sign (if the effects of their Ohmic resistance be neglected). That is to
say the synchronous motor N will also be the seat of two rotary fields moving with
the speed
but in contrary directions, and these fields cannot attain an appreciable
intensity as they have to pass through the said annular screen of bars E of the
inducer J. But if by any means, the inducer J of the synchronous motor be started
with a speed = 0, the field turning in the same direction with it will only have a
speed
relatively to the screen, while the other will have a speed of + Ω
T
T
relatively thereto.
T
The synchronous motor N in consequence of its screen, will
assume a speed very near which allows of its synchronisation by introducing into
7'
the inducing coil D a continuous current supplied from any source.
The synchronism having been obtained, the screen will have no farther action on
the field which turns in the same direction with it while it will almost entirely
prevent the development of the field rotating in the contrary direction.

page_text: But the field produced by the coil D of the revolving inducer will be added on to
the existing rotary field, and can increase its action to any desired extent.
The necessary equality between the electromotive forces in the coils C¹ C² . .
and C5 C6.
mounted in opposition, will cause the production in the asynchronous
motor M. of a single magnetic field. turning in the same direction as the synchronous
motor N. As the intensity of this field only depends upon the intensity of the field
developed in the synchronous motor N, it will increase with the magnetising force of
the inducing coil D of the latter without the inducer I of the asynchronous motor
being required to furnish dewatted currents for developing this field. Under these
conditions there will not only be generated in the asynchronous motor M a powerful
field which renders it capable of starting under a load, but this field is in reality
created by the continuous current that passes through the inducing coil D of the
synchronous motor N, so that the intensity of the dewatted currents which the supply
circuit has to furnish to the asynchronous motor M can be rendered nul and even
negative even at the moment of starting.
When once the asynchronous motor M is started and has acquired a speed of
, a magnetic field which will move with the speed relatively to the
rotation =
inducer I thereof, will only have a speed of
T
T
-
relatively to the induced
-
, as will also be
circuits. These will be the seat of currents of the frequency
the armature circuits of the motor M.
T
-
T
The asynchronous motor M, the speed of rotation of which will always be
proportional to the frequency 2, will consequently gradually slacken in speed,
and when the motor M has arrived at its normal speed, the synchronous motor N
1
will only revolve with a very slow speed which in general, if _
1 and 2 revolutions per second.
T
= 40, will be between
This fact is very important. In effect, the auxiliary synchronous motor N will
only have to revolve at a quick speed during the very short time of starting the
asynchronous motor.
It is therefore possible to make it assume at the moment of starting the motor M,
a speed of rotation which would be inadmissible if it had to be continued any length
of time, on account of the heating of the bearings. Also, there may be included,
for the specific induction in its masses of iron, values which would also be inadmissible
if the variations of flux require normally to have a high frequency.
This will enable the auxiliary motor to be made of comparatively small dimensions
relatively to those of the asynchronous motor.
What has been said above relatively to a motor with single phase currents is
equally applicable to. a motor with polyphase currents; it is only necessary to
replace the described inducer I of the asynchronous motor M. Figure 1 by one having
polyphase circuits.
The only difference would consist in the initial production of a single rotary field
by this new inducer and in the fact that the auxiliary motor N will start of itself.
The magnetic screen with which the inducer of the auxiliary motor was assumed to
be provided would in this case no longer be necessary for preventing the formation
of rotary fields turning in the contrary direction to the motors, but it will still be
necessary to maintain it in order to insure the rapid starting and maintenance of
motion of the auxiliary synchronous motor.
The principle of this invention may be stated as follows:-
Assuming an asynchronous motor with mono or polyphase alternating currents,
the induced circuits of which include n bobbins shifted respectively through an
angle equal to (n being greater than 2), there is firstly combined with it an
2 πT

page_text: -
auxiliary synchronous motor which runs idle and the armature of which also has
n bobbins shifted through an angle of 21; and secondly, the n induced bobbins of
n
the asynchronous motor are coupled with the corresponding bobbins of the armature
of the synchronous motor.
This arrangement being made, the inducing circuit of the asynchronous motor is
connected with the working circuit, and the synchronous motor is started, its
armature being fed by the currents developed by induction in the induced circuits
of the asynchronous motor. The synchronous motor owing to the presence of its
magnetic screen, will assume a speed very near synchronism.
It is then connected up and its inducer supplied with a continuous current from
any convenient source, whereupon the asynchronous motor will be automatically
started.
Other inventors, such for instance as Messrs. Bradley and Swinburne have already
proposed to combine a synchronous motor with a motor with rotary field, either with
the view of rendering equal to I the proportion between the actual and apparent
work supplied to the motor by the main distributing circuit, or, with a view to
generating in suti currents shifted in phase relatively to the single current supplied
by the distributing circuit. But in this case the synchronous motor is always
directly supplied by the distributing circuit, and acts either in a similar manner to
a condenser, supplying the asynchronous motor with the dewatted currents necessary
for its excitation, or it acts as phase transformer, in drawing from the distributing
circuit the energy required for producing currents shifted as to phase relatively to
the single current supplied by the distributing circuit; or again, it acts in both
the above ways conjointly.
In
In this case the mode of working of the rotary field motor employed is in no way
modified by the addition of the synchronous motor, such as last described.
particular the phenomena of self induction of which it is the seat, will always have
the effect of reducing the value of its maximum couple for a certain voltage. The
addition of the synchronous motor does not modify in any way the properties of the
motor; it only facilitates its supply from the distributing circuit.
Lastly, the synchonous motor employed must always supply a considerable actual
and apparent amount of work and must revolve at a high speed.
On the other hand, by combining, according to this invention, the synchronous
motor with the induced circuits of the asynchronous motor, the properties of the
latter are entirely modified in rendering nought the coefficient of apparent self
induction of its induced circuits.
This has the effect of very considerably increasing the maximum value of the
couple that this motor can develop under a certain voltage.
Moreover, the auxiliary motor will in this case not run at a high speed and furnish
a considerable apparent amount of work, except at the moment of starting. This
enables a motor of only small dimensions to be used, upon which demands for
assistance are only made from time to time.
Thus not only is the present invention quite distinct from what has been before
proposed, but it is much more efficacious and only requires a very much smaller
amount of auxiliary material.
At the moment of starting the auxiliary synchronous motor, as there is no opposing
electromotive force except the small one due to chemical resistances etc. of the several
circuits of the two motors, the current supplied by the line to the inducing circuit of
the asynchronous motor would acquire a very great intensity which would be very
disadvantageous both as regards the motors and the consequent lowering of the
voltage in the supply circuit. This inconvenience is obviated by introducing rheostats
with variable resistances such as R¹ R². . Figure 3 in the several circuits
connecting the induced coils of the asynchronous motor with the armature coils of
the synchronous motor, as shewn in the diagram at Figure 3. There would be
introduced into these circuits all the available resistances before closing the connection

page_text: between the distributing circuit and the inducer of the asynchronous motor and
these resistances would be cut out as soon as the synchronous motor was started.
These resistances can also be utilised in another way. Assuming that the
asynchronous motor requires to be started at frequent intervals; it would be
inconvenient to have to start the synchronous motor each time,
In such a case
therefore the said resistances would be reintroduced when the former has to be
stopped, and they would then stop the passage of the current necessary for the
production of an appreciable couple in the asynchronous motor so as to stop this, but
they would allow the passage of watted currents of very small intensity, requisite for
maintaining the rotation of the synchronous motor. This latter would increase in
speed in proportion as the speed of the asynchronous motor diminished, and would
be always in readiness to effect the fresh starting of the asynchronous motor.
With regard to the starting of the above described motors the following is to be
observed.
If the asynchronous motor is one with poly phase currents, the synchronous motor
will start of itself.
adopted.
If the asynchronous motor has single phase currents, it will be necessary to start
the synchronous motor, and in this case the direction of rotation of the asynchronous
motor will only depend upon the direction in which the synchronous motor was
started. For starting the latter it will in most cases be sufficient to give it an
impulse by hand. If its size is too great for this, the following expedient may be
Referring to the diagram Figure 4, the armature of the synchronous motor is
provided with two special starting circuits S and C which at the one end are connected
together and to the return lead of the supply circuit Y Y. In the one circuit S is
included, in series therewith, a self induction coil or a condenser L, and in the
other C is included a resistance K, a switch as at CC being provided, for changing
the connections so as to introduce either the coil or condenser 1, or the resistance K
according as the synchronous motor is to run in the one direction or the other. The
other ends of the two circuits L and R are also connected together and to the contact
plate of a switch D whereby either the starting circuits of the synchronous motor, or
the inducer I of the asynchronous motor can be connected to the supply lead X X of
the main circuit.
Of course, any other arrangement may be employed whereby the starting of an
asynchronous motor with monophase currents can be effected.
For exciting the synchronous motor, if no source of continuous current is available,
it will be sufficient to generate on the spot the necessary current by transforming one
of the currents that serve to supply its armature.
It is to be observed that the difference of potential at the terminal clamps of each
of these circuits will decrease with the speed of rotation of the motor while the
intensity of the currents which passes through them remains constant. Conse-
quently the transformer to be mounted on the axis of the synchronous motor must
be connected in series in one of the circuits of its armature, and not in shunt between
the extremities of the circuit.
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 :-
1. In asynchronous motors worked by mono- or poly-phase alternating
currents, the method of combining a synchronous motor with an asynchronous
motor whose induced part is provided with n circuits (n being greater
than 2) shifted in phase, and connected separately to corresponding arma-
ture circuits of the synchronous motor which is arranged to utilize
alternating currents shifted in phase by period, and whose exciting coils receive
1th
n
n
a supply of continuous current, a rheostat with variable resistance being introduced
into each of the said circuits thus formed between the induced circuits of the

page_text: asynchronous motor and the armature circuits of the synchronous motor, and the
armature of the latter being provided with a magnetic screen which opposes all
variation of magnetic flux, substantially as described.
2. The construction of combined asynchronous and synchronous motors arranged
and operating as herein described with reference to the drawings.
Dated this 16th day of November 1897.
ABEL & IMRAY,
Agents for the Applicant.