Improvements in Continuous Current Dynamos for either Generating or Receiving Electrical Energy.
Year: 1893

page_text: Date of Application, 4th Dec., 1893
Complete Specification Left, 9th Aug.. 1894-Accepted, 15th Sept., 1894
TRUVIDIONAL ENCIFICATION.
I'
Improvements in Continuous Current Dynamos for either Generating
or Receiving Electrical Energy.
We, MAURICE HUTIN, of No. 46, Rue Caumartin, Paris, Engineer, and
MAURICE LEBLANC, of No. 63, Allee du Jardin Anglais, Le Rainey, Seine and
Oise, France, Engineer, do hereby declare the nature of this invention to be as
follows:-
Our invention has for its object, firstly, to prevent the occurrence of Foucault
currents in the field magnets or inductors of dynamos having armatures of the
Paccinotti kind by a more economical method than that which consists in
making the inductor of laminated plates.
These Foucault currents, are, as is well known, produced by the passage of the
teeth or projections between the grooves of the armature in front of the enlarge-
ments of the polar pieces. Secondly, the object is to avoid, in continuous current
machines having any description of armature, the accidents that may result from
either the breaking of a circuit or a sudden variation in the load. As is known,
the whole potential energy which is stored up in the several parts of the dynamo
in this case suddenly assumes the form of extra current.
The principle of our invention consists in the application to continuous current
dynamos closed circuits arranged round the polar enlargements of the field magnets,
which we have termed 'deadening circuits," and which we have applied to
alternate current machines as described in the Specification to our Patent
No. 13765 of 1892.
For the above purposes,, taking for example a machine of the "Manchester
ype, in which the armature consists of a cylinder whose outer surface is formed
with teeth, or longitudinal grooves, the separate windings that are laid between,
the teeth or in the grooves being connected to the commutator as in the case
of a Gramme ring. The field magnets are formed of solid metal, and the polar
enlargements that partly surround the armature are fitted at the sides with two
rings of non magnetic metal that will offer but little resistance to the passage
of electric currents, such as bronze or copper; these rings are connected together
by bolts of the same material extending across the concave surface of the polar
enlargements, and secured to the rings by screwing or rivetting so as to insure
a good contact.
The provision of this deadening circuit will have the following effect. When
the armature revolves between the polar fields, the number of its teeth which are
momentarily situated opposite the polar enlargements is not always the same,
and it follows from this that the permeability of the magnetic circuit formed by
the field magnets, the armature, and polar connecting pieces will vary periodically;
the variation of the permeability causes a corresponding variation in the value
of the lines of force passing through the field magnets, moreover, the lines of force
or magnetic flux passing through one particular tooth of the armature will
gradually decrease as it approaches the extreme edge of the polar enlargement,
and on passing beyond it, they will become zero. There consequently results
increasing and decreasing fluctuations of the magnetic flux near the extremities
of the polar enlargements, and a fluctuation in the mean direction of the magnetic
flux round, the centre of the armature.
'
To state this action shortly, we may say, firstly, that the passage of the teeth of
a Pacciuotti ring under the polar enlargements causes variations in the value of the

page_text: magnetic flux circulating in the inducing magnetic circuit; and secondly, the
passage of these same teeth causes an oscillation of the mean direction of
the inducing flux round the centre of the ring.
In what we have stated above, we assume that the influence of the reaction of
the induced part is neglected; this reaction, as is known, has the effect of causing
the mean direction of the flux passing through the polar connecting pieces to turn
through a certain angle round the centre of the ring or armature, and it will have
the effect of displacing the mean position of the before mentioned oscillations of
the flux, but these oscillations will nevertheless exist.
•
The effect upon the above described action produced by the before described
deadening circuit, which constitutes a séries of electric circuits of very low
resistance on the surface of the iron, will be as follows.
If the magnetic flux passing through were constant, there would be no action;
but if the flux varies, then owing to the high degree of conduction of the said
circuits, there will be produced in the deadening device currents of considerable
intensity representing a great expenditure of energy.
The expenditure of energy necessary for causing the magnetic flux to vary
under these conditions being much greater than that required for maintaining it
constant, it will remain constant, and no Foucault currents will be produced in the
field magnets.
The said deadening circuits can be applied to various constructions of dynamos,
such for example as that in which the armature core is built up of a number of
discs, side by side, the winding being constituted by bars or rods passing through
holes in the said discs.
:
The application of the deadening circuit also has the following advantage.
It will be seen how difficult it is to produce in the system constructed as
described a sudden variation of the magnetic flux which passes through the
deadening device.
Assuming now that a breaking of one of the circuits of the machine takes place,
the potential energy of the machine, the value of which is necessarily a function of
the supply of electrical energy required, would ordinarily sink to zero in a very
short time.
The deadening circuit will in that case act as moderator and the variation of
energy stored in the machine can only take place slowly. This effect may be
explained as follows.
In a closed circuit the quantity of energy expended by the passage of a current
is proportional to the square of the intensity; the ohmic resistance being given, it
results that the energy expended in the closed circuit is proportional to the square
of the variation of the magnetic flux traversing the same. This quantity of
energy will be inversely as the resistance; on the other hand the variation of the
quantity of potential energy stored up in the machine is proportional to the
variation of the corresponding magnetic flux; this quantity of energy reduced to
the unit of time is therefore simply proportional to the rate of the variation of
the 'flux relatively to the unit of time.
Dated this 4th day of December 1893.
ABEL & IMRAY,
Agents for the Applicants.
COMPLETE SPECIFICATION.
Improvements in Continuous Current Dynamos for either Generating.
or Receiving Electrical Energy.
: We, MAURICE HUTIN, of No. 46 Rue Caumartin, Paris, Engineer, and
MAURICE LEBLANC, of No. 63 Allee du Jardin Anglais, Le Raincy, Seine and
Oise, France, Engineer, do hereby declare the nature of this invention and in what

page_text: manner the same is to be performed, to be particularly described and ascertained
in and by the following statement:-
Our invention has for its object, firstly to prevent the occurrence of Foucault
currents in the field magnets or inductors of dynamos having armatures of the
Paccinotti kind by a more economical method than that which consists in making
the inductor of laminated plates.
"
These Foucault currents, are, as is well known, produced by the passage of the
teeth or projections between the grooves of the armature in front of the
enlargements of the polar pieces.
་་
Secondly, the object is to avoid, in continuous current machines having any
description of armature, the accidents that may result from either the breaking of
a circuit or a sudden variation in the load. As is known, the whole potential
energy which is stored up in the several parts of the dynamo in this case suddenly
assumes the forin of extra current.
i
The principle of our invention consists in the application to continuous current
dynamos closed circuits arranged round the polar enlargments of the field magnets,
which we have termed "deadening circuits" and which we have applied to alternate
current machines as described in the Specification to our Patent No. 13765
of 1892.
29
For the above purposes, taking for example a machine of the "Manchester
type, such as is shewn in longitudinal section and end view at Figs. 1 and 2 of the
accompanying drawings in which the armature d consists of a cylinder whose outer
surface is formed, with teeth, or longitudinal grooves the separate windings that
are laid between the teeth or in the grooves being connected to the commutator, as
in the case of a Gramme ring. The field magnets are formed of solid metal, and
the polar enlargements a that partly surround the armature are fitted at the sides
with two rings of non magnetic metal that will offer but little resistance to the
passage of electric currents, such as bronze or copper; these rings are connected
together by bolts c of the same material extending across the concave surface of
the polar enlargements, and secured to the rings by screwing or rivetting so as to
insure a good contact.
K
The provision of this deadening circuit will have the following effect. When
the armature d revolves between the polar fields, the number of its teeth which
are momentarily situated opposite the polar. enlargements is not always the same,
and it follows from this that the permeability of the magnetic circuit formed by
the field magnets, the armature, and polar connecting pieces will vary periodically';
the variation of the permeability causes a corresponding variation in the value
of the lines of force passing through the field magnets. We have shewn
diagrammatically at Figs. 3 and 4 two positions of the teeth relatively to the
polar field; it will be seen that at Fig. 3 the number of teeth, serving for the
passage of the flux is 10; in Fig. 4 it is 11. It will be evident therefore that
each of these relative positions will correspond to a different value of the flux.
Moreover, the lines of force or magnetic flux passing through one particular tooth
of the armature will remain practically constant while the tooth passes along the
polar field .but will gradually decrease as it approaches the extreme edge of the
polar enlargement, and on passing beyond it, they will become zero. There
consequently result increasing and decreasing fluctuations of the magnetic flux
near the extremities of the polar enlargements, and an oscillation of the mean
direction of the magnetic flux round the centre of the armature.
To state this action shortly, we may say, firstly, that the passage of the teeth of
a Paccinotti ring under the polar enlargements causes variations in the value of
the magnetic flux circulating in the inducing magnetic circuit; and secondly, the
passage of these same teeth causes an oscillation of the mean direction of the
inducing flux round the centre of the ring.
In what we have stated above, we assume that the influence of the reaction of
the induced part is neglected; this reaction, as is known, has the effect of causing
the mean direction of the flux passing through the polar connecting pieces to turn

page_text: through a certain angle round the centre of the ring or armature, and it will have
the effect of displacing the mean position of the before mentioned oscillations of
the flux, but these oscillations will nevertheless exist.
The effect upon the above described action produced by the before described
deadening circuit, which constitutes a series of electric circuits of very low
resistance, on the surface of the iron, will be as follows.
If the magnetic flux passing through were constant there would be no action;
but if the flux varies, then owing to the high degree of conduction of the said
circuits, there will be produced in the deadening device currents of considerable
intensity representing a great expenditure of energy.
The expenditure of energy necessary for causing the magnetic flux to vary under
these conditions being much greater than that required for maintaining it constant,
it will remain constant, and no Foucault currents will be produced in the field
magnets.
"
The said deadening circuits can be applied to various constructions of dynamos,
such for example as that in which the armature core is built up of a number of
discs, side by side, the winding being constituted by bars or rods passing through
holes in the said discs. Such an arrangement is shewn at Fig. 5, where the winding
is constituted by rods or bars. h passing through holes in the discs y forming the
armature core. h are the rings forming, together with the bolts c the above
described deadening circuit.
The application of the deadening circuit also has the following advantage.
It will be seen how difficult.it is to produce in the systein constructed as described
a sudden. variation of the magnetic flux which passes through the deadening
device.
" ་་་་
+
Assuming now that a breaking of one of the circuits of the machine takes place,
the potential energy of the machine, the value of which is necessarily a function
of the supply of electrical energy required, would ordinarily sink to zero in a very
short time.
7"
.
The deadening. circuit will in that case act as moderator and the variation of
energy. stored in the. machine can only take place slowly. This effect may be
explained as follows.
In a closed circuit the quantity of energy expended by the passage of a current
is proportional to the square of the intensity; the ohmic resistance being given, it
results that the energy expended in the closed circuit is proportional to the square
of the rate of variation of the magnetic flux traversing the same. This quantity
of energy will be inversely as the resistance; on the other hand the variation of
the quantity of potential energy stored up in the machine is proportional to the
variation of the corresponding magnetic flux; this quantity of energy reduced to
the unit of time is therefore simply proportional to the rate of the variation of the
flux relatively to the unit of time. Consequently the work expended in heating
the circuits will be proportional to the square of the derivative of the flux while
the restitution of potential energy will be simply proportional to such derivative.
With a circuit of sufficiently low resistance the potential energy of the machine
could only disappear slowly.
From what has been stated above we draw the following conclusions.
1. All sudden change in the working of the machine which has the effect of
changing the value of the potential energy stored up therein, will cause a restitution
of energy in the form of heat in the deadening circuits, that is to say in circuits of
strong composition and not easily susceptible to deterioration.
2. The restitution of energy can only take place slowly if the deadening circuits
have a sufficiently low ohmic resistance:
( +
2.
Having now particularly described and ascertained the nature of this inven
tion and in what manner the same is to be performed, we declare that what
we claim is :-
1
1. The use in continuous current machines of deadening circuits consisting of

page_text: nou magnetic metal discs or rings having only a low resistance to the passage of
the electric current placed on either side of the polar extensions of the field
magnets and connected together by transverse rods or bolts of the same metal,
substantially as described.
2. The use of the deadening circuits referred to in the first claim for suppressing
Foucault currents in the field magnets of dynamo machines having armatures of
the Paccinotti description, whether such armatures be formed with peripheral
teeth or grooves or with holes formed through the periphery, through which the
induced circuits are passed, substantially as described.
3. The use of the deadening circuits referred to in the first claim for obviating
the detrimental effect produced in all continuous current dynamo machines upon the
delicately constructed portions thereof, by the restitution of the potential energy
resulting from sudden changes in the working of the system, substantially as
described.
Dated this 8th day of August 1894.
ABEL & IMRAY,
Agents for the Applicants..