Method of and Appliances for Exciting Alternating Current Dynamo Machines, whether Acting as Generators or as Motors.
Year: 1898

page_text: Date of Application, 7th Oct., 1898
Complete Specification Left, 20th May, 1899- Accepted, 19th Aug., 1899
Method of and Appliances for Exciting Alternating Current Dynamo
Machines, whether Acting as Generators or as Motors.
I, CHARLES DENTON ABEL, of Birkbeck Bank Chambers, Southampton Build-
ings, Chancery 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'Eléctricité, of 13, Rue Lafayette, Paris, France, Manufacturers)
to be as follows:-..
This invention relates to a new method of exciting alternating current dynamo
machines with constant potential of the Hutin and Leblanc system, whether
acting as generators or as motors, and whether, having synchronous or
asynchronous motion.
As is known, the exciting machine of the said system not only requires to
run synchronously with the dynamo which it supplies, but also, it must pass
through the same positions in space at the moments when the dynamo passes
through determined positions. In other words, if we assume that the two
machines have the same number of poles, their connection must be such that
not only their axes perform the same number of revolutions per second but
that their relative positions always remain the same no matter what are the con-
ditions under which the machines operate.
Such a connection may be effected in the simplest possible manner when the
two machines have the same number of poles, at is then suffices to fix them on
one and the same axis, but this solution can only be applied when the dynamo
has a weak polarity and runs at a great speed. It is evident that it would not.
be practicable in the case of an alternator running at a very small angular speed.
The exciting machine would in this case require to have very large dimensions
relatively to its power.
An equivalent connection between the axes of the two machines having
different polarities and consequently different angular velocities can be effected
by means of trains of wheels. This solution, which is indicated in the Specifica-
tion to Patent No. 22333 of 1896, presents however inconveniences, in particular
if it is proposed to apply the new exciting machine to an already existing dynamo
where there has consequently been no provision for such a train of gearing. It
would, therefore, be very advantageous to be able to do away with all mechanical
connection between the dynamo and its exciting machine.
The present invention has for its object an improved method of excitation
which fulfils this condition. In the Specification to Patent No. 22333 of 1896
it is stated that the fixed coils through which the currents passing from the
brushes flow develop a magnetising force at every moment equal to and of the
contrary sign to that which the same currents develop in traversing the movable
circuits of the exciting machine connected in shunt between the contacts of its

page_text: collector. In other words, the continuous or alternating currents of low frequency
issuing from the brushes do not produce any flux in the armature. This con-
dition can only be fulfilled if the number of turns of the fixed coils have deter-
mined values and if the positions which they occupy round the movable rings
have been suitably chosen.
I will assume that this is not the case and that the fixed coils develop not
only a flux equal and of contrary sign to that developed by the movable circuits
connected to the collector of the exciting machine but also a flux X of which the
direction will form an angle of 90° with that of the flux Y if the machine has
90°
22
only two poles and an angle equal to if it has two n poles.
a
n
Under these conditions, the current passing from the brushes will develop in
the machine a constant flux which is fixed in space if these currents are con-
tinuous, or a flux of constant intensity but revolving with the speed if the
currents are alternating and of a frequency a and if the machine has 2 n poles.
We will suppose that the exciting machine then revolves synchronously with
the dynamo which it supplies. In the first case the alterating currents coming
from this dynamo which pass through the special movable circuits of the exciting
machine develop a flux of constant intensity and fixed in space. In the second
case they produce a constant flux and intensity but they revolve in space with a
speed
a
―,
ሃኒ
Consequently, in both cases, there will occur the production of a couple on the
axis of the exciting machine, the strength of which will depend both upon the
strength of the fluxes generated by the fixed and movable circuits and upon the
angle formed by their directions.
The exciting machine, once synchronised, will continue in both cases to turn
with the same speed as the dynamo, taking from the currents supplied by the
latter the necessary energy for its working; but this exciting machine can then
be assimilated to a revolving transformer, which receiving alternating currents
of a determined frequency gives cither a continuous current or alternating
currents of a different frequency.
In order that the electromotive force developed between the brushes may
always remain proportional to the intensity of the resulting flux developed by
the alternating currents issuing from the dynamo, which pass through the special
movable circuits of the exciting machine, it is necessary that the number of
turns of the fixed inducing circuit shall be sufficiently small.
But this revolving transformer, excited in the manner above described, possesses
a remarkable property, which my correspondents have discovered by calculation
and verified experimentally. Whatever may be the variations of the supply
from the exciting machine, and consequently the variations of the resisting couple
developed on its axis, not only will this machine turn synchronously with the
dynamo which it supplies, but the relative positions of their axes remain invariable
as though they were connected together by a train of wheels. It results from
this that nothing is changed in the working of this exciting machine although
all mechanical connection between it and the dynamo which it supplies has been
done away with.
I will describe by way of example one arrangement of apparatus for carrying
the said invention into practice, referring for this purpose to the accompanying
drawing, in which Fig. 1 shews a sectional plan and Fig. 2 an end view of an
exciting machine intended to supply an ordinary alternator with a continuous
current while Figs. 3 to 5 shews diagrams of the connections and action.
The machine is shewn with six poles, and is supposed to be combined with an
alternator working with three-phase currents.
On one and the same axis 0 Fig. 1 are mounted rings A and B which carry
the coils S¹ S¹ and Sª Sª for alternating currents, each including three circuits.

page_text: On the axis O are also arranged three rings c¹² and d¹d d³, connected to
those of the alternator through the medium of brushes, as indicated in the
diagram Fig. 3, where I II III are the terminals of the circuits of the alternator,
S the circuits of the ring A of the exciting machine, S2 the circuits of the ring B
and a the circuits of the armature of the alternator. Generally, either the
voltage of the alternator will be too high for subjecting the exciting machine to
it, or its current supply would be too great for the currents to be readily brought
to the ring A by causing them to pass through the brushes of the rings.
It will in these cases be advisable to interpolate a transformer in the circuit
of the currents passing to the rings A and B. In certain cases it may be advisable
to do this for all the circuits as shewn at Fig. 4, where T, are the transformers.
ZZ Fig. 1 are coils through which passes the continuous current, and which
are connected to the collector C on which bear the six brushes as shewn at
Fig. 2.
The ring A revolves within the inducer D and the ring B within the inducer E.
These two inducers are constructed in the ordinary way and have six poles.
Their coils have the same number of turns but the cores of the inducer E
has a smaller section than those of D), as shewn at Fig. 1, thus affording different
degrees of permeability for the magnetic circuits in these cores.
It is assumed that in the polar enlargements of each of the inducers there
is introduced a cylindrical cage of bars e e, forming magnetic screens which have
the effect of insuring the synchronous motion of the exciting machine, and per-
mitting the same general construction to be employed, whether the machine
has to excite an alternator with single phase alternating currents, or one with
polyphase currents.
The position of the brushes must be capable of adjustment.
For starting and regulating the exciting machine, as above described, it is
assumed that a continuous current generator is available for exciting the alter-
nator when this only performs the work of starting its exciting machine, operat-
ing in that case as synchronous motor.
This auxiliary generator can of course be of very small dimensions and as it
will only be used for starting, it can be made available for all the alternators
of a central station.
This generator will be connected in series.
The method of starting is as follows. The alternator is excited by a con
tinuous current after having disconnected it from the circuits for alternating
currents of the exciting machine. The latter is then started with continuous
current and is brought up to the same speed as the alternator. The connections
of the alternator and exciting machine circuits are then re-established, and the
latter will then revolve as a synchronous motor and will supply a continuous
electromotive force; the auxiliary continuous current machine is then thrown
out of circuit.
Referring now to Fig. 5, a group of six interruptors I I is in the first instance
introduced in the six conductors leading from the alternator to the exciting
machine, these interruptors being arranged to be actuated simultaneously.
Secondly the exciting machine, the auxiliary continuous current exciter and
the inducer R Fig. 5 of the alternator are then connected in series. The inducer 1
of the exciting machine will also be shunted by a rheostat m', of which the
resistance can be rendered zero. The armature of the exciting machine is also
shunted by a rheostat m². Lastly, an interruptor J enables the auxiliary exciter
to be short circuited.
Thirdly, two of the interruptors of the group I close shunt circuits of lamps 1 12,
the variation in brightness of which will enable the differences of motion between
the alternator and the exciter to be observed during the starting period.
The alternator being set in motion by the auxiliary exciter the exciting machine
will start as ordinary continuous current motor. Its speed can be regulated by
means of the rheostat m², until the lamps show that synchronism is attained.

page_text: At this moment the interruptor II is closed and the exciting machine will con-
tinue to run synchronously with the alternator.
The shunt established between the brushes of its collector is then gradually
eliminated during which time the inducer of the continuous current machine is
short circuited.
When this has been done, the auxiliary exciter is short circuited and eliminated
from the system.
It will always be necessary to provide for a regulation between narrow limits,
if it be desired to maintain an exact voltage under given conditions. For this
purpose a coil Si. Fig. 5 with variable self induction and with three circuits is
provided in the circuits of the currents passing from the alternator to the ring B,
and a rheostat M is provided in the circuit of the inducer R of the alternator.
When asynchronous dynamos are to be supplied by the exciting machine, it
suffices to replace its inducer with continuous current, such as is shewn at Figs. 1
and 2, by an inducer with rotary field, having as many circuits as the dynamo
has induced circuits.
The starting of the exciting machine will be effected in the same way as above
described, and the asynchronous dynamo is provisionally transformed into an
ordinary alternator, by sending the current supplied by the continuous current
exciting machine into one of the induced circuits of the dynamo. This continuous
current will flow through the single circuit of the exciting machine, which will
be in shunt between the terminals of the induced circuit."
For regulating, it will be advisable to employ as many rheostats as the dynamo
contains induced circuits, all such rheostats being operated simultaneously.
Dated this 7th day of October 1898.
ABEL & IMRAY,
Agents for the Applicant.
Method of and Appliances for Exciting Alternating Current Dynamo
Machines, whether Acting as Generators or as Motors.
I, CHARLES DENTON ABEL, of Birkbeck Bank Chambers, Southampton Build-
ings, Chancery 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'Eléctricité, of 13, Rue Lafayette, Paris, France, Manufacturers)
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 a new method of exciting alternating current dynamo
machines with constant potential of the Hutin and Leblanc system, whether
acting as generators or as motors, and whether having synchronous or
asynchronous motion.
As is known, the exciting machine of the said system not only requires to
run synchronously with the dynamo which it supplies, but also, it must pass
through the same positions in space at the moments when the dynamo passes
through determined positions. In other words, if we assume that the two
machines have the same number of poles, their connection must be such that
not only their axes perform the same number of revolutions per second but
that their relative positions always remain the same no matter what are the con-
ditions under which the machines operate.
Such a connection may be effected in the simplest possible manner when the

page_text: two machines have the same number of poles, at is then suffices to fix them on
one and the same axis, but this solution can only be applied when the dynamo
has a weak polarity and runs at a great speed. It is evident that it would not
be practicable in the case of an alternator running at a very small angular speed.
The exciting machine would in this case require to have very large dimensions
relatively to its power.
An equivalent connection between the axes of the two machines having
different polarities and consequently different angular velocities can be effected
by means of trains of wheels. This solution, which is indicated in the Specifica-
tion to Patent No. 22333 of 1896, presents however inconveniences, in particular
if it is proposed to apply the new exciting machine to an already existing dynamo
where there has consequently been no provision for such a train of gearing. It
would, therefore, be very advantageous to be able to do away with all mechanical
connection between the dynamo and its exciting machine.
The present invention has for its object an improved method of excitation
which fulfils this condition. In the Specification to Patent No. 22333 of 1896
it is stated that the fixed coils through which the currents passing from the
brushes flow develop a magnetising force at every moment equal to and of the
contrary sign to that which the same currents develop in traversing the moveable
circuits of the exciting machine connected in shunt between the contacts of its
collector. In other words, the continuous or alternating currents of low frequency
issuing from the brushes do not produce any flux in the armature. This con-
dition can only be fulfilled if the number of turns of the fixed coils have deter-
mined values and if the positions which they occupy round the movable rings
have been suitably chosen.
-
n
if it has two n poles.
Cl
I will assume that this is not the case and that the fixed coils develop not
only a flux equal and of contrary sign to that developed by the moveable circuits
connected to the collector of the exciting machine but also a flux X of which the
direction will form an angle of 90° with that of the flux Y if the machine has
90°
only two poles and an angle equal to
Under these conditions, the current passing from the brushes will develop in
the machine a constant flux which is fixed in space if these currents are con-
tinuous, or a flux of constant intensity but revolving with the speed if the
currents are alternating and of a frequency a and if the machine has 2 n poles.
We will suppose that the exciting machine then revolves synchronously with
the dynamo which it supplies. In the first case the alterating currents coming
from this dynamo which pass through the special movable circuits of the exciting
machine develop a flux of constant intensity and fixed in space. In the second
case they produce a constant flux and intensity but they revolve in space with a
speed
ab
n
n
Consequently in both cases, there will occur the production of a couple on the
axis of the exciting machine, the strength of which will depend both upon the
strength of the fluxes generated by the fixed and movable circuits and upon the
angle formed by their directions.
The exciting machine, once synchronised, will continue in both cases to turn
with the same speed as the dynamo, taking from the currents supplied by the
latter the necessary energy for its working; but this exciting machine can then
be assimilated to a revolving transformer, which receiving alternating currents
of a determined frequency gives either a continuous current or alternating
currents of a different frequency.
In order that the electromotive force developed between the brushes may
always remain proportional to the intensity of the resulting flux developed by
the alternating currents issuing from the dynamo, which pass through the special

page_text: movable circuits of the exciting machine, it is necessary that the number of
turns of the fixed inducing circuit shall be sufficiently small.
But this revolving transformer, executed in the manner above described, possesses
a remarkable property, which my correspondents have discovered by calculation
and verified experimentally. Whatever may be the variations of the supply
from the exciting machine, and consequently the variations of the resisting couple
developed on its axis, not only will this machine turn synchronously with the
dynamo which it supplies, but the relative positions of their axes remain invariable
as though they were connected together by a train of wheels. It results from
this that nothing is changed in the working of this exciting machine although
all mechanical connection between it and the dynamo which it supplies has been
done away with.
I will describe by way of example one arrangement of apparatus for carrying
the said invention into practice referring for this purpose to the drawings accom-
panying my Provisional Specification, in which Fig. 1 shews a sectional plan and
Fig. 2 an end view of an exciting machine intended to supply an ordinary alter-
nator with a conitnuous current while Figs. 3 to 5 shew diagrams of the con-
nections and action.
The machine is shewn with six poles, and is supposed to be combined with an
alternator working with three phase currents.
On one and the same axis O Fig. 1 are mounted rings A and B which carry
the coils S S and S2 S2 for alternating currents, each including three circuits.
On the axis O are also arranged three rings c¹ c² c³ and d¹³ ³, connected to
those of the alternator through the medium of brushes, as indicated in the
diagram Fig. 3, where I II III are the terminals of the circuits of the alternator,
S₁ the circuits of the ring A of the exciting machine, S2 the circuits of the ring B
and a the circuits of the armature of the alternator. Generally, either the
voltage of the alternator will be too high for subjecting the exciting machine to
it, or its current supply would be too great for the currents to be readily brought
to the ring A by causing them to pass through the brushes of the rings.
It will in these cases be advisable to interpolate a transformer in the circuit
of.the currents passing to the rings A and B. In certain cases it may be advisable
to do this for all the circuits as shewn at Fig. 4, where T, are the transformers.
ZZ Fig. 1 are coils through which passes the continuous current, and which
are connected to the collector C on which bear the six brushes as shewn at
Fig. 2.
The ring A revolves within the inducer D and the ring B within the inducer E.
These two inducers are constructed in the ordinary way and have six poles.
Their coils have the same number of turns but the cores of the inducer E
have a smaller section than those of D, as shewn at Fig. 1 thus affording different
degrees of permeability for the magnetic circuits in these cores.
It is assumed that in the polar enlargements of each of the inducers there
is introduced a cylindrical cage of bars e e, forming magnetic screens which have
the effect of insuring the synchronous motion of the exciting machine, and per-
mitting the same general construction to be employed, whether the machine
has to excite an alternator with single phase alternating currents, or one with
polyphase currents.
The position of the brushes must be capable of adjustment.
For starting and regulating the exciting machine, as above described, it is
assumed that a continuous current generator is available for exciting the alter-
nator when this only performs the work of starting its exciting machine, operat-
ing in that case as synchronous motor.
This auxiliary generator can of course be of very small dimensions and as it
will only be used for starting, it can be made available for all the alternators
of a central station.
This generator will be connected in series.
The method of starting is as follows. The alternator is excited by a con-

page_text: tinuous current after having disconnected it from the circuits for alternating
currents of the exciting machine. The latter is then started with continuous
current and is brought up to the same speed as the alternator. The connections
of the alternator and exciting machine circuits are then re-established, and the
latter will then revolve as a synchronous motor and will supply a continuous
electromotive force, the auxiliary continuous current machine is then thrown
out of circuit.
Referring now to Fig. 5, a group of six interruptors I I is in the first instance
introduced in the six conductors leading from the alternator to the exciting
machine, these interruptors being arranged to be actuated simultaneously.
Secondly the exciting machine, the auxiliary continuous current exciter and
the inducer R Fig. 5 of the alternator are then connected in series. The inducer ¹
of the machine will also be shunted by a rheostat m', of which the
resistance can be rendered zero. The armature of the machine A is also shunted
by a rheostat m². Lastly, an interruptor J enables the auxiliary exciter 6 to be
short circuited.
Thirdly, two of the interruptors of the group I close shunt circuits of lamps 112,
the variation in brightness of which will enable the differences of motion between
the alternator and the exciter to be observed during the starting period.
The alternator being set in motion by the auxiliary exciter the exciting machine
will start as ordinary continuous current motor. its speed can be regulated by
means of the rheostat m², until the lamps 12 show that synchronism is attained.
At this moment the interruptor I I is closed and the exciting machine will con-
tinue to run synchronously with the alternator.
The shunt established between the brushes of its collector is then gradually
eliminated during which time the inducer of the continuous current machine is
short circuited.
When this has been done, the auxiliary exciter is short circuited and eliminated
from the system.
It will always be necessary to provide for a regulation between narrow limits,
if it be desired to maintain an exact voltage under given conditions. For this
purpose a coil Si. Fig. 5 with variable self induction and with three circuits is
provided in the circuits of the currents passing from the alternator to the ring B,
and a rheostat M is provided in the circuit of the inducer R of the alternator.
When asynchronous dynamos are to be supplied by the exciting machine, it
suffices to substitute for its inducer with continuous current, such as is shewn
at Figs. 1 and 2 an inducer with rotary field, having as many circuits as the
dynamo has induced circuits.
The starting of the exciting machine will be effected in the same way as above
described, and the asynchronous dynamo is provisionally transformed into an
ordinary alternator, by sending the current supplied by the continuous current
exciting machine into one of the induced circuits of the dynamo. This continuous
current will flow through the single circuit of the exciting machine, which will
be in shunt between the terminals of the induced circuit."
For regulating, it will be advisable to employ as many rheostats as the dynamo
contains induced circuits, all such rheostats being operated simultaneously.
Having now particularly described and ascertained the nature of this invention
and in what manner the same is to be performed I declare that what I claim is :-
The herein described method of exciting any synchronous or asynchronous
motor or generator operating with alternating currents of one or of many phases
by providing with a collector and brushes an exciting machine the same as a
continuous current dynamo but arranged to revolve in fields developed :-
(a) By passage through special circuits wound on its armature, either
alternating currents furnished and employed by the main dynamo and
currents furnished in shunt from the network conductors, or by the same
currents first transformed by ordinary transformers:—

page_text: (b) By passage of currents from brushes bearing on the collector of the
exciting machine in inducing circuits like those of an ordinary alternator
if the exciting machine is for an alternator or in inducing circuits of a
machine having a revolving field if the exciting machine is for an
asynchronous dynamo, in which case the number of the inducing circuits
of the exciting machine should equal that of the induced circuits of the
dynamo.
The exciting machine is simply branched on the same net work as the alternator
and the asynchronous dynamo which it excites; it is started in any way and then
operates as a revolving transformer which, on the one hand, acts as a synchronous
motor receiving the necessary energy from the net work, and on the other hand,
produces the required exciting currents.
Dotad this 20th day of May 1899