Improvements in Dynamo Electric Machines.
Year: 1890

page_text: Date of Application, 25th Oct., 1890
Complete Specification Left, 24th July, 1891-Accepted, 12th Sept., 1891
PROVISIONAL SPECIFICATION.
Improvements in Dynamo Electric Machines.
I, GEORGE PITT, of Sutton, in the County of Surrey, Gentleman, (a communi-.
cation to me from abroad by René Thury, Electrical Engineer, residing in Geneva,
10 Rue Voltaire, Switzerland,) do hereby declare the nature of this invention to be
as follows:-
In the construction of so called unipolar dynamos a serious inconvenience is
experienced which up to the present time has prevented the industrial employment
of these machines by limiting to a small amount, the energy capable of being drawn
from them. This inconvenience exists in the fact that the flow of magnetic force
is diverted by the current and made to turn in the direction of the rotation of the
armature or part in which the current is induced and it does this the more easily
the more uniform the magnetic field. By destroying the uniformity of the field by
giving a special form to the polar surfaces, this inconvenience is partially removed
but only by creating others by which the advantage these machines have over
multipolar machines is lost.
"
I have found that the most efficacious means for removing this grave defect
consist in the employment of two similar armatures moving in different directions
or one turning in relation to the other which is fixed; they are contained in the
same space between the magnet poles or "entrefer and they are connected either
in series or quantity. It results from this arrangement that the current produced
in one of the armatures balances exactly the re-action of the other armature
because it flows in the opposite direction and it is of the same intensity. It is not
necessary that the two armatures should move at the same speed for the re-action
is produced by the current and not by the movement; for this reason one of the .
armatures may be fixed provided it is similar to the other.
The lines of force in place of turning or inclining take the form of the letter S
when the intensity becomes considerable but this tendency is small in consequence
of the high value which may be given to the field. This can be done without
inconvenience for Foucault currents have not to be combated, these may be entirely
avoided by uniformity of the field.
Besides, two armatures placed in the same entrefer have the advantage of
allowing the electro motive force which the machines can maintain to be doubled.
and thereby renders their application more general and their construction more
economical.
The construction which I prefer is that which makes use of an armature in the
form of a disc. Nevertheless it is possible to vary in many ways the form of the
armature and the arrangement of the inducers. For example, an armature in
the form of a drum may be made in accordance with this arrangement, but not
being able to describe all machines which realize the invention above set forth I
limit myself to the description of two types which are represented by the annexed
drawing.
The principle of double induction is also applicable to multipolar machines with
continuous winding or sectional winding as is practised, for example, in alternating
current machines, and its application permits a more complete utilization of the
magnetic fields avoiding the diminution of the magnetic force which results from
excessive torsion of the lines of force. It is particularly applicable to machines
with radial winding.
In the drawing annexed
T
Lancelled uninolar machines

page_text: furnished with armatures arranged on the system described above, with a fixed
disc d.
Figure 1 shows an armature consisting of a disc rotating in a uniform magnetic
field furnished by the tubular, magnet M.. The current developed in the disc d
passes from the centre to the exterior, for example, is collected by the brush >> fixed
at the exterior of a second disc d' which leads back the current towards the centre,
traversing in the opposite direction the same entrefer. The brush 6' .communicates
directly with the terminal + and thus with the exterior circuit.
The reaction of the current passing in the second disc d¹ is exactly equal to the
reaction produced upon the field by the disc d but of different sign and thus prevents
the lines of force from turning, the reactions annulling each other.
In Figure 2 the arrangement is similar only the armature is in the form of a
drum. For ordinary machines with continuous winding the application of the
system takes the form of a winding arranged against the polar surfaces.
Dated this 25th day of October 1890.
CARPMAEL & Co.,
Agents.
COMPLETE SPECIFICATION.
Improvements in Dynamo Electric Machines.
I, GEORGE PITT, of Sutton, in the County of Surrey, Gentleman, (a commu-
nication to me from abroad by René Thury, Electrical Engineer, residing in Geneva,
10 Rue Voltaire, Switzerland,) do hereby declare the nature of this invention and
in what manner the same is to be performed to be particularly described and ascer-
tained in and by the following statement :—
In the construction of so called unipolar dynamos a serious inconvenience is
experienced which up to the present time has prevented the industrial employment
of these machines by limiting to a small amount, the energy capable of being drawn
from them. This inconvenience arises from the fact that the flow of magnetic
force is diverted by the current and made to turn in the direction of the rotation of
the armature or part in which the current is induced and it does this the more casily
the more uniform the magnetic field. By destroying the uniformity of the field by
giving a special form to the polar surfaces, this inconvenience is partially removed
but only by creating others by which the advantage these machines have over
multipolar machines is lost.
I have found that the most efficacious means for removing this grave defect
consist in the employment of two similar armatures moving in different directions
or one turning in relation to the other which is fixed; they are contained in the
same space between the magnet poles or "entrefer" and they are connected either
in series or quantity. It results from this arrangement that the current, produced
in one of the armatures balances exactly the re-action of the other armature
because it flows in the opposite direction and it is of the same intensity. It is not
necessary that the two armatures should move at the same speed for the re-action
is produced by the current and not by the movement; for this reason one of the
armatures may be fixed provided it is similar to the other.
The lines of force in place of turning or inclining take the form of the letter S
when the intensity becomes considerable but this tendency is small in consequence
of the high value which may be given to the field. This can be done without
inconvenience for Foucault currents have not to be combatted, these may be entirely
avoided by uniformity of the field.
Besides, two armatures placed in the same entrefer have the advantage of
allowing the electro motive force which the machines can maintain to be
doubled, this renders their application more general and their construction more
economical.
The construction which I prefer is that which makes use of an armature in the

page_text: form of a disc. Nevertheless it is possible to vary in many ways the form of the
armature and the arrangement of the inducers. For example, an armature in
the form of a drum may be made in accordance with this arrangement, but not
being able to describe all machines which realize the invention above set forth
I limit myself to the description of two types which are represented by the annexed
drawing.
The principle of double induction is also applicable to multipolar machines with
continuous winding or sectional winding as is practised, for example, in alternating
current machines, and its application permits a more complete utilization of the
magnetic fields avoiding the diminution of the magnetic force which results from
excessive torsion of the lines of force. It is particularly applicable to machines
with radial winding.
In the drawing left with the Provisional Specification Figures 1 and 2 shew in
section two arrangements of so called unipolar machines furnished with armatures
arranged on the system described above, with a fixed disc. Figure 1 shows an
armature consisting of a disc rotating in a uniform magnetic field furnished by the
tubular magnet M. The current developed in the disc d passes from the centre to
the exterior, for example, is collected by the brush 6 fixed at the exterior of a
second disc d' which leads back the current towards the centre, traversing in the
opposite direction the same entrefer. The brush b' communicates directly with the
terminal and thus with the exterior circuit.
The reaction of the current passing in the second disc d' is exactly equal to the
reaction produced upon the field by the disc d but of different sign and thus prevents
the lines of force from turning, the reactions annulling each other.
In Figure 2 the arrangement is similar only the armature is in the form of a
drum.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
The employment in dynamo electric machines of a compensating circuit annulling
the reaction of the armature upon the field in the form of a second armature similar
to the first in the same entrefer and traversed by a current equal to that in the first
armature substantially as described.
Dated this 21st day of July 1891.
CARPMAEL & Co.,
Agents for the Applicant.