Improvements in and Means or Apparatus for Rectifying Alternating Currents for Working Continuous Current Motors, and for Electrolytical Purposes.
Year: 1892

page_text: Date of Application, 2nd Nov., 1892
Complete Specification Left, 27th July, 1893-Accepted, 28th Oct., 1893
PROVISIONAL SPECIFICATION.
Improvements in and Means or Apparatus for Rectifying Alternating
Currents for Working Continuous Current Motors, and for
Electrolytical Purposes.
I, CHARLES POLLAK, of Rückerstrasse 14, Frankfort on the Main, Germany
Electrical Engineer, do hereby declare the nature of this invention to be as
follows:-
--
The working of continuous current electro motors and the performance of
chemical work by means of an alternating current has heretofore been practicable
only by employing the alternating current to drive an alternating current electro
motor and connecting with the latter a generating dynamo which would give off a
continuous current at its current collector. Now this invention has for object to
substitute for these converters or transforming devices a simple apparatus which
will convert the alternating current into a pulsating or intermittent (continuous
direction) current, in such a manner that the regular oscillations of the current
strength and of the tension can be reduced to any desired small amount.
Figure 1 of the accompanying diagrams illustrates the course of a simple
alternating current. If this current be rectified by a commutator the course will
assume the form shown in Figure 2. It is now desired to employ this rectified
current or only that portion of it in which the variations in tension do not exceed a
is intended to
determined amount. For example the curve shown in Figure
represent diagrammatically the variations in tension in successive periods, in which
the end values lie between O and M, 0 and 150 volts; whilst the tension may
amount to 50 and 100 volts at the intermediate points indicated at R in Figures 3
and 4. If it be now desired to employ only that portion of the course of the
current shown in Figs. 3 and 4, within which the tension limits are 50 and 150 volts,
and 100 and 150 volts respectively, there is required a rectifying apparatus which
will take the successive alternating current impulses at those times when the tension
has reached 50 or 100 volts, or any desired amount.
According to my invention I employ an apparatus (rectifier) for the aforesaid
purposes, which can be carried out in various ways and of which I will now describe
two examples.
From a source of alternating current (generating dynamo or transformer) two
conductors lead to two rubbing rings of a rotary disc (of the rectifier), the ends of
these conductors form brushes which rub on the said rings. The rectifier is caused
to rotate synchronously with the movement of the primary source of alternate
This can
current or proportionately to the number of alternations of said current.
be effected by driving by means of belts, by means of an alternate current electro
motor, or by means of other devices, and requires but little power, as merely the
brush friction is to be overcome. On the circular surface of the rectifier are
arranged strips or lamellae of good conducting material in such a manner as to be
alternately in contact with the two rubbing rings, and every two consecutive
lamellae are separated by insulating spaces increasing in width outwardly. The
lamellae come into contact with a pair of diametrically oppositely arranged
collecting brushes which can be rotated about the axis of the disc of the rectifier,
and also adjusted in a radial direction. According to the distance of the brushes
from the centre of the disc there is taken either a uniformly pulsating current
(Fig. 2) or an intermittent succession of current impulses (Figs. 3 and 4) which can
be employed for driving electro motors or for performing chemical work. The
position of the brushes should be chosen so that the current is taken at that moment
when its electro motive force is equal to the electro motive counter-force in the

page_text: motor or electrolytical bath, that is to say, the current strength is nil; by this
means sparking is obviated at the stepping or converting points.
When the brushes are in one position a pulsating continuous current is taken,
whereas when differently placed an intermitting current of say 50 or 100 volts
tension may be taken. By rotating the brushes about the axis of the disc they
may be brought into the neutral position.
In some cases the rectifier may be of drum shape and rotated as has been before
stated; the lamellae in this case run to a point, as also the intermediate surfaces.
The brushes are capable of rotation about the axis of the drum and are adjustable
in the longitudinal direction thereof, and the action is as with the first example.
When it is desired to take current for overcoming a constant electro motive
force, there may also be employed a drum shaped rectifier, or a flat rectifier can be
used, in which the intermediate spaces are all equal one to the other and have a
width corresponding to the tensions.
By my invention I obtain a recifier moving as before stated synchronously with
the alternating current source or moving with a speed proportionate to the number
of alternations of this current and by arranging the current-conducting lamellae of
said rectifier at a distance from one another only a determined portion of the
rectified current is taken by the brushes; or in some cases the apparatus may be
so arranged that the current-conducting lamellae may be arranged at a varying
distance from one another and so that the spaces between the lamellae run to a
point whereby the successive alternating current impulses are capable of being
taken at those moments when the tension has reached a desired value.
By arranging the taking off brushes in such a manner that these brushes can
rotate as before mentioned about the axis of the rectifier and are also adjustable in
the longitudinal direction of the lamellae, I am enabled to take currents of any
desired tension with the same brushes, and to enable the brushes to be brought into
the neutral position, and sparking is prevented by the inclusion of the electro-
motive counter-force in the conductor or circuit of the taking-off brushes.
Dated this 2nd day of November 180°)
COMPLETE SPECIFICATION.
Improvements in and Means or Apparatus for Rectifying Alternating
Currents for Working Continuous Current Motors, and for
Electrolytical Purposes.
I, CHARLES POLLAK, of Rückerstrasse 14, Frankfort on the Main, Germany,
Electrical 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 :-
Up to the present time it has been possible to drive direct-current-motors and
perform chemical work by means of an alternating current, only by using the
alternating current to drive an alternating-current-motor, and joining to the latter
a generating machine or dynamo, which delivered a direct current to its commutator.
The present invention has for an object to provide, in place of these transformers, a
simple apparatus which shall change the alternating current into a pulsating or
intermittent direct current, in such a manner that the regular variations in current
strength and potential can be reduced to as small a degree as desired.
Fig. 1 of the accompanying drawing illustrates the course of a simple alternating
current. If this current be rectified by means of a commutator, the course assumes
the form represented in Fig. 2. It is now merely a question of using this rectified
current, or only that portion of the same in which the variations of the potential do
not exceed a certain limit. For example, the curve represented in Fig. 2 is supposed

page_text: to portray the variations of potential in the successive current waves (periods), where
the limiting values between O and M are 0 and 150 volts, while in Figs. 3 and 4
at the intermediate points shewn at R, the potential may amount to 50 or 100 volts.
If now it be desired to use only that part of the course of the current represented
in Figures 3 and 4, within which the limits of potential are 50 and 150 volts,
or 100 and 150 volts, a commutating device is required, which shall take off the
successive alternating current impulses at those moments in which the potential
of 50 or 100 volts, or any desired value, is reached.
The subject matter of the present invention, therefore, consists of a device
(rectifier or commutator), such as represented diagrammatically in Figs. 5—14.
In Fig. 5, W denotes a source of alternating current (generating machine or
transformer) from which two conductors are carried to two contact rings S S, of a
rotary disc (of the rectifier or commutator). The ends of these conductors form
brushes, which rest upon the rings S S. There is imparted to the commutator a
rotation synchronous with the motion of the primary source of alternating current,
or proportional to the number of alternations of said current. This can be effected
by means of alternating current motors, belting, or other devices, and only requires
a small expenditure of work, since only the friction of the brushes is to be overcome.
Strips L L of good conducting material are arranged upon the circular surface of
the commutator in such a manner as to be alternately in contact with the two
contact rings S S and that every two successive strips are separated by insulating
spaces JJ, which increase outwardly in width. On the strips there slide a pair of
brushes B B, arranged diametrically opposite each other, for taking the current,
which are capable of rotation about the axis of the disc of the commutator and are
also adjustable in a radial direction. According to the distance of the brushes
from the middle of the disk, there will be taken off either a uniformly pulsating
current (Fig. 2) or an intermittent succession of current impulses (Figs. 3 and 4),
which can be employed for driving motors or for doing chemical work. The
position of the brushes should be such that the current is taken off at that moment
when its electromotive force is equal to the counter electromotive force present in
the motor or electrolytical bath, that is to say, when the current strength is nil;
consequently the formation of sparks is prevented at the points of transition.
In the position B' B¹ of the brushes, a pulsating direct current, and in the
positions B2 B2, B3 B3, an intermittent direct current of 50 or 100 volts potential is
taken off. By rotating the brushes about the axis of the disc, they are brought
into the neutral position.
The commutator shewn in Fig. 6 is of drum shape. In this figure again
W denotes the source of alternating current, S S the contact rings, L L the strips,
JJ the intermediate spaces of insulating material or the air insulation, and B B
the taking-off brushes. The drum shaped commutator is set in rotation in the
manner mentioned above. The strips run to a point, as also do the intermediate
spaces, the brushes are capable of being rotated about the axis of the drum, and
are adjustable in the direction of their length.
The operation is, as can be seen, the same as described with reference to Fig. 5;
the three positions B1, B2, B3, of the brushes correspond again to the curves,
Figs 2, 3, 4.
When it is a question of taking off a current for overcoming a constant electro-
motive force, there can also be employed a drum-shaped commutator of the kind
shewn in Fig. 7, or a flat commutator, in which the intermediate spaces J have all
the same width corresponding to the potential.
In some cases the strips may be made of the form represented in Figs. 8 and 9,
that is, they run to a point in alternately opposite directions, the change in the
width of the intermediate spaces may then be effected by shifting the two com-
mutator halves thus formed in the longitudinal direction of the axis, as shewn in
Figs. 8 and 9. B B are the brushes for taking off the current.
The arrangement thus described is also applicable to commutators of disc-form;

page_text: but in such case the two halves of the commutator must be shifted in a radial instead
of in an axial direction.
Brushes more or less thick, or a number of thin ones, adjustable in relation to
each other, may be employed.
First if brushes of, for example, cm., thicknesses are used, and are replaced by
brushes, of say, 1 cm., thickness, then it is obvious that the taking off of the current
lasts longer in the second case, because the thicker brush comes in contact with
the strips sooner and glides off these later than the thin brush.
If several thin brushes metallically connected with each other and relatively
adjustable, Fig. 10, are employed, and they are arranged side by side so that they
all stand in one and the same straight line, Fig. 11; then, during the revolution
of the commutator, the current is taken from the strips L by the brushes B B
corresponding to the width of the strips. If one or several brushes B B B or Bº Bº B°
(Fig. 10) be shifted in reference to the other or others for example, by half the
width of the strips L, Fig. 12, the taking off of the current will last one and a half
times longer. By further shifting the brushes, for example as in Fig. 13, the taking
off will last twice, and as in Figs. 10 and 14, three times, longer, because in the
latter case before the brush first reaching the strip leaves it, the second already
comes in contact with the same strip, and then the third, before the second brush
has left the strip.
The regulation described is also applicable to the commutator of disc form shewn
at Figure 5.
The several apparatus herein before described can also be employed for trans-
forming direct current, for instance from accumulators, into alternating current, by
supplying direct current to the contact rings, and actuating the apparatus in any
manner whatever. If the apparatus is to work as a shunt (in parallel) with an
alternating current machine, the motor which drives it must be put in synchronous
movement by the machine-current itself, or in any other way, by which means,
among other advantages, accumulators also can be employed in alternating current
plants.
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 I do
not limit myself, or lay claim, to any particular mechanical details of construction,
or to any special mechanical means for distancing, sliding, giving motion to, or
otherwise adjusting the parts composing my means for rectifying alternating
currents, as ordinary or well known mechanisms, such as screw motions, slides,
cams, and other devices, commonly known and used by mechanicians, may be
employed to obtain the motions, and adjustments of the parts as and for the
purposes herein fully described, therefore what I claim is :
1. A commutator capable of working synchronously with a source of alternating
current, that is to say, moving with a speed proportional to the number of alter-
nations of said current, the current-conducting strips of which are at such a distance
from each other that only a determined portion of the rectified current is taken off
by the brushes subtantially as described.
2. A commutator as claimed by Claim 1, wherein the taking-off of any desired
amounts of the rectified alternating current by means of two or more taking-off
brushes is effected by rendering the relation between the width of the strips and
that of the intermediate spaces variable by the arrangement of the straight strips
in a circular surface, and by making the brushes also adjustable, all substantially
as and for the purposes described with special reference to Fig. 5 of the accom-
panying drawing.
3. In commutators of the kind specified in Claim 1, the current-conducting strips,
in drum-shaped arrangement, tapering in the same direction, and the taking-off
brushes, arranged to be adjustable axially all substantially as and for the purposes
:described with special reference to Fig. 6 of the accompanying drawings.

page_text: 4. A commutator of the kind specified in Claim 1, but wherein the relation
between the width of the strips and that of the intermediate spaces can be varied
by axially or radially shifting the strips lying in a cylindrical casing or in a
circular surface respectively, the said strips running alternately to a point in
opposite directions, Figs. 8 and 9 all substantially as and for the purposes
described.
5. A disc shaped or drum shaped commutator of the kind specified in Claim 1
but wherein the proportion between the width of the strips, and that of the spaces
between the same, remains invariable, and only the thickness of the brushes is
varied, or several brushes electrically connected together, which are revolvable
about the commutator-axis, are so arranged, relatively to each other, that the
taking-off of the current lasts a longer or shorter time, substantially as described
with reference to Figs. 10 to 14 of the accompanying drawings.
7. A commutator for the delivery of alternating current from sources of direct
current, as previously claimed, the said commutator being kept in motion by, for
example, an alternating-current-motor, or by other suitable device, and where (in
the first case) the driving motor can be fed either by a part of the produced alter-
nating current itself, or by the current of an alternating-current-machine, so that
the working of accumulators in parallel with alternating-current-machines is
rendered possible, substantially as herein set forth.
17th of Tal., 1902
BREWER & SON,
Agents.