Improvements in Apparatus for Transforming Alternating into Continuous Electrical Currents, or Conversely.
Year: 1896

page_text: Date of Application, 30th Jan., 1896
Complete Specification Left, 17th Sept., 1896-Accepted, 14th Nov., 1896
PROVISIONAL SPECIFICATION.
[Communicated from abroad by LA SOCIÉTÉ ANONYME POUR LA TRANSMISSION
DE LA FORCE PAR L'ELECTRICITÉ, of 13 Rue Lafayette, Paris, France.]
Improvements in Apparatus for Transforming Alternating into
Continuous Electrical Currents, or Conversely.
I, JOHN JMRAY, of No. 28 Southampton Buildings, Chancery Lane, in the
County of London, Consulting Engineer and Chartered Patent Agent, do hereby
declare the nature of this invention to be as follows:-
According to this invention a continuous current dynamo machine which may have
2 n poles has fixed on the axis of its armature two conducting rings counected to
the armature, on which rings bear two brushes connected to the leads of alternating
currents, these brushes being situated at the extremities of the arc of ring equal
to Around the armature is fixed a magnetic screen consisting of a number of
copper rods arranged at equal intervals all round the armature, passing through
and between the polar extensions of the field magnets as near as practicable to the
periphery of the armature.
12
Alternating currents led to the rings by the two brushes above mentioned cause
the armature to revolve, generating a continuous current, which is led away by
the ordinary commutator and its brushes. Or, conversely, a continuous current
led to the ordinary commutator brushes causes revolution of the armature
generating alternating currents which are led away by the rings and its brushes.
The magnetic screen surrounding the armature prevents the production of any
flux varying in intensity or direction within the machine.
Dated this 30th day of January 1896.
ABEL & IMKAY,
Agents for the Applicant.
Improvements in Apparatus for Transforming Alternating into
Continuous Electrical Currents, or Conversely.
J, JOHN IMRAY 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 and in what manner the same is to be
performed to be particularly described and ascertained in and by the following
statement:-
According to this invention, apparatus for transforming single phase alternating
currents into continuous currents, or conversely, is constructed as I will describe
with reference to the accompanying drawing, Fig. 1 of which shews a cross section
while Fig. 2 shews a longitudinal section of the apparatus.

page_text: For the purpose of this invention any continuous current dynamo, which may be
assumed to be bipolar for simplicity of explanation has provided on its armature
shaft two rings a and b, on which bear two fixed brushes a b' which are respectively
connected to two diametrically opposite contacts of the collector.
If an alternating current be sent into the armature by means of the brushes a¹
and and the rings a and b, this machine can be made to act as a synchronous
motor with single phase current by exciting its field magnets by a continuous
current, and imparting motion to the machine at starting. Under these conditions,
a continuous current can be collected between the brushes F and F which bear
upon the collector.
Conversely, if a continuous current be sent through the brushes F and F into
the machine, it will be constituted a continuous current motor, and a single phase
alternating current can be obtained therefrom in a circuit connected to the
brushes a and b¹.
It will however be readily seen that such an arrangement would not work well.
The armature, having an alternating current passing through it will tend to produce
two fluxes of constant intensities and rotating relatively thereto with the speed of
synchronism, but in contrary directions. The flux which rotates in the direction
contrary to that of the rotation of the machine, would be stationary in space and
would oppose the flux developed by the passage of the continuous current. The
other flux on the contrary would travel through space at a speed double that of
synchronism, and will consequently flow at that speed through the windings of the
armature which are short circuited by the brushes of the collector.
This flux will produce parasite currents consuming a large amount of energy, and
it would be impossible to arrange the brushes so as to avoid sparking.
It is therefore necessary to adopt means for suppressing such variable flux in
order to obtain a practical result.
This might be effected by strongly saturating the armature by the field magnets;
but this cannot be done when the frequency of the alternating currents to be
produced or utilised exceeds 25 or 30, which is generally the case in practice. The
losses through hysterisis in the armature core would be inadmissable.
According to the present invention the desired result is obtained in a very simple
manner, by surrounding the armature with a magnetic conducting screen which
will oppose the development of all variable flux whether as regards intensity or as
regards direction.
This screen is constituted as shewn on the drawing, by a series of copper rods
such as m n, arranged regularly all round the armature and passing through the
polar extensions of the field magnets at a point as near as possible to the clearance
space between them and the armature. These bars are all connected together at
their ends by means of lateral conducting rings A A.
This arrangement is applicable to all constructions of continuous current
machines whether multipolar or bipolar but in the case of a machine with 2 n poles
the two rings for the entrance and issue of the alternating current must be connected
to contacts of the collector forming an angle equal to between each other.
72
The arrangement may also be applied with advantage in cases where it is
desired to transform polyphase alternating currents into continuous currents and
conversely.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed I declare that what I
claim is
Apparatus for transforming an alternating single phase current iuto a continuous
current, or the converse, consisting of a continuous current machine of any known
construction on the shaft of which are arranged two rings connected separately to
two contacts of the collector, which, for a machine with 2 n poles, are placed at an

page_text: angle of to each other while the rotating armature is surrounded by a magnetic
screen having for its object to prevent the production of all variable flux, whether
as to intensity or as to direction, in the clearance space between the armature and
the field magnets, substantially as described.
Dated this 16th day of September 1896.
ABEL & IMRAY,
Agents for the Applicant.