Improvements in Dynamo Electric Machines.
Year: 1896

page_text: Date of Application, 15th Feb., 1896
Complete Specification Left. 16th Nov., 1896-Accepted, 13th Feb., 1897
PROVISIONAL SPECIFICATION.
Improvements in Dynamo Electric Machines.
SEBASTIAN ZIANI DE FERRANTI, 27 Charterhouse Square in the County of
London, Electrician and Engineer, do hereby declare the nature of this invention
to be as follows:-
This invention has for its object improvements in dynamo electrical machines
whereby the efficiency is increased, the weight of copper diminished and sparking
at the brushes is eliminated.
It is well known that in dynamo electric machines the distortion and diminution
of the magnetic field is produced by the increase of current flowing in the
armature. In order to avoid this I wind the pole faces with a conductor with the
main current from the machine flowing in it, in the opposite direction and in a
similar position as the current flowing in the armature.
According to my invention I make this conductor, which forms the face winding
of the pole of iron where it is opposite and complete the circuit by means of
conductors of copper or other non-magnetic metal brazed, sweated welded or
otherwise fixed to the ends of the iron.
By making the conductors in the magnetic field of iron I avoid the losses due to
the magnetic resistance of the air, the iron conductors not only taking the current
but also conveying the magnetic lines of force from the field to the armature.
In some cases where it is difficult to provide sufficient section of iron to carry the
necessary current in the armature I electroplate the iron bars with copper so as to
add to their conductivity.
In some cases I solder or braze copper strips along the sides of the iron conductors
so as to provide the additional extra conductivity for the current to be carried.
My invention applies not only to continuous current generators of the two polar
and multipolar type but is also applicable to so called unipolar machines. In this
latter case the iron conductors are placed upon the face of the standing circular
pole and have the currents from the disc or drum passed through them in an
opposite direction to that flowing in the drum or disc.
When my invention is applied to continuous current machines I further diminish
the sparking at the brushes by the use of reversing poles placed in between the
main poles of the machine and magnetised by the compensating winding already
described.
In some cases I may form the conductors of the compensating winding of a
segmental section so as to get the maximum amount of material into the circular
space at disposal.
These conductors 1 may form around the inside of an iron ring, the copper
joining conductors which form the segmental conductors into coils and which
project from the sides of the machine may be encased in brass or other metal rings.
The conductors may all be held in position by filling up with sulphur or other
insulating compound between the conductors and the brass or non-magnetic rings.
In some cases I may form the iron conductors of strips of iron of parallel section
and may use copper strips of V section to fill up the space and provide the
additional conductivity which is sometimes necessary.
The reversing poles may be segmental in shape very similar to the section of the
iron conductors and may be carried from the inside of the iron containing ring

page_text: already mentioned. This iron, containing ring when fitted complete with its
non-magnetic rings and conductors may be placed within the circle of the main
poles of the machine. The armature is placed within the ring containing the
compensating conductors.
I, SEBASTIAN ZIANI DE FERRANTI, of Hollinwood, in the County of Lancaster,
late of 27 Charterhouse Square, in the County of London, Electrician and Engineer
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 :-
This invention has for its object improvements in dynamo electrical machines..
whereby the efficiency is increased, the weight of copper is diminish...
sparking at the brushes eliminated.
It is well known that in dynamo electric machines, distortion and diminution of
the magnetic field is produced by the increase of current flowing in the armature.
In order to avoid this, I wind the pole-faces with conductors in which the main
current from the armature flows, the direction in wbich the current flows being
opposite to that in which it is flowing in the conductors on the armature immediately
beneath them.
According to my invention I make this conductor, which forms the face-winding
of the pole, of iron, where it is passed along the face of the pole, and I complete
the electric circuit by means of conductors of copper or other non-magnetic metal
attached to the iron.
In order that my said invention may be fully understood, I will now describe it
in connection with the drawings hereunto annexed, having reference to the letters
and figures marked thereon, like letters referring to similar parts in the several
figures.
Fig. 1, is a general diagram showing the conductors and connections.
Fig. 2, is a section of a single pole wound according to one of my methods.
Fig. 3, is a similar pole wound in a different manner,
Fig. 4, is a similar pole wound in a different manner.
Fig. 5, is a longitudinal section through a complete pole ring.
Fig. 6, is a cross-section through same.
Fig. 7, is an outside view of same.
In Fig. 1, 1 show conductors, A, attached to the face of the pole piece, B, in
that part which is opposite to the conductors, C, on the armature, D.
These conductors, A, are made of iron and are insulated from the pole, B, and
from one another by the insulating material, E, shown by thick dark lines.
The ends of these conductors, A, are connected to one another by the con-
nections, F, shown by means of full lines where they cross the armature on the
front ends and by dotted lines where they cross at the back end, in such a manner
that the current entering at the end, G, will leave at the end, H, after successively
traversing each conductor, A.
These connections, F, are made of brass, copper or other non-magnetic metal,
which is either brazed, sweated or welded, or otherwise fixed into the end of
the iron.
By making the conductors, A, which are in the magnetic field, of iron, I avoid

page_text: the loss due to the magnetic resistance of the air, the iron conductors not only
taking the current, but also conveying the magnetic lines of force from the fiel
magnet, B, towards the armature, D.
In Fig. 2, I show a single pole, B, with the iron conductors, A, dovetailed into
the face of the magnet, B, and insulated therefrom and from one another by the
insulating material, E. It will be seen that by this method of construction the
iron conductors, A, are held firmly in position without further fixing being
necessary.
In some cases it is difficult to provide a sufficient section of iron to carry the
necessary current for completely neutralizing the reaction due to the current
in the armature, this is owing to the comparatively high electrical resistance
of iron.
In
In order to overcome this difficulty I sometimes prefer the arrangement shown
in Fig. 3, which shows strips, I, of brass, copper, or other metal, having a low
electrical resistance attached to the sides of the conductors, A, wound on the face
of the magnet, B, and insulated from one another and from the magnet by means
of insulating strips, E. The strips, I, being in complete electrical connection
with the iron strips, A, serve to convey a considerable portion of the current.
Fig. 4, I show wound on the face of the pole, B, strips of iron, A, which have been
covered with a layer K of copper or other metal having low electrical resistance
which has been electrically deposited on the iron bars, A, the compound bar thus
formed is as in previous cases insulated from the magnet, B, by means of the
insulating strips, E.
The end connections in both these cases are inade by means of non-magnetic
metal strips connected to the conductor on the face of the poles.
In order that I may better commutate the current in armatures of continuous
current machinery without moving the brushes as the load varies, I make use of
reversing poles placed midway between the main poles of the dynamo. I show
one method of performing this in Figs. 5, 6 & 7 in which the poles are shown to be
formed on the inner surface of the ring of iron.
Fig. 6 shows a cross section through a ring fitted with four poles. The poles
are formed of iron conductors, A, insulated by the layer of insulating material, E,
from the ring, B.
Midway between the poles I form subsidiary poles, C, by attaching iron strips
to the ring and I fill up the space between the main poles, A, and the reversing
poles C, by means of non-magnetic metal strips, D, which serve to carry the
current round the reversing pole, C, in order to magnetize it and produce the necessary
magnetic field for changing the direction of the current in the armature coils as
they undergo commutation.
I connect the ends of the iron conductors, A, and the non-magnetic conductors, D,
by means of copper strips F, in such a manner that the direction of the current in
the conductors, A, is opposite to the current in the conductors of the armature
immediately beneath them.
These end connections, F, are enclosed in annular boxes, G, fitted into each end
of the main ring, B, and in some cases the space between the connections, F, and
the box, G, is filled up with insulating compounds.
The complete pole ring when wound, and when the end boxes, G, have been
fitted onto the ring, B, as shown in Fig. 7, is then placed in position between the
magnets of the dynamo and the armature is placed within the complete ring thus
formed.
Although I have described this invention as applied to continuous generators or
motors of the ordinary two-pole or multipolar type, I would have it understood
that I may apply this method of construction to unipolar dynamos, in which case
the iron conductors are fitted upon the face of the standing circular pole in similar
manner to those described in connection with the two-pole dynamos and the current
from the revolving dises or drums is passed through them in the opposite direction
to that in which it flows in the discs or drums.

page_text: Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is :-
1. In dynamo electric machinery, the placing of insulated strips of iron on the
face of the poles and connecting them by means of non-magnetic metal strips in
such a manner as to convey a current in a direction contrary to that in which the
current flows in the armature conductors in order to neutralize the armature
reactions as described.
2. In dynamo electric machines, the placing of compound insulated strips con-
sisting of iron on which copper has been electrically deposited or iron to which
copper or brass strips have been attached and so connecting these compound strips
by means of strips of non-magnetic metal so as to convey a current in a contrary
direction to that in which the current is flowing in the armature conductors.
3. In dynamo electric machinery a pole ring consisting of a ring of iron having
main poles formed on the inner surface by means of insulated iron strips and
subsidiary reversing poles surrounded by strips of non-magnetic metal, the whole
being so connected by non-magnetic metal strips as to convey a current in an
opposite direction to that in which the current is flowing in the armature
conductors.
4. In dynamo electric machinery the construction of a pole ring consisting of
main poles formed of insulated iron strips, subsidiary reversing poles surrounded
by non-magnetic metal strips on the inner surface of an iron ring with non-magnetic
connections enclosed in non-magnetic aunular boxes, as described and illustrated in
Figs. 5, 6 & 7.
5. The improvements in dynamo electric machines substantially as described and
illustrated in Figs. 1 to 7.
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