Improvements in Rectifiers for Electrical Currents.
Year: 1895

page_text: Date of Application, 5th Jan., 1895-Accepted, 9th Feb., 1895
COMPLETE SPECIFICATION.
Improvements in Rectifiers for Electrical Currents.
I, WILLIAM BURROWES CLOSE, of 39 Adelaide Street East, in the City of
Toronto, in the County of York in the Province of Ontario, Canada, 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:—
My invention relates to improvements in rectifiers for converting an alternating
current into a steady or constant current and the object of the invention is to devise
such a rectifier as will register with the varying phases of the current in such a
manner that the connection of 'the commutator with the brushes will be changed as
to the alternations exactly on the zero line of the cycle of undulations and thereby
prevent the burning out of the rectifying commutator and it consists essentially of
a motor run from an independent source, a dynamo the fields of which are run from
a shunt circuit from the alternating current wires, a commutator of peculiar
construction having its brushes connected to the main alternating current wires and
brushes for leading off the constant current, the armatures of the motor and
dynamo and the peculiarly constructed commutator being all secured to a common
shaft and the different parts being otherwise constructed as hereinafter more
particularly explained.
Fig. 1, is a perspective view of my alternating current rectifying machine.
Fig. 2, is a cross section through the peculiar form of commutator.
In the drawings like letters of reference indicate corresponding parts in each
figure..
Heretofore in machines of this class the great difficulty has been that the
commutator would be burned out or destroyed by sparking on account of the
alternating current being cut during the period that the current is flowing and not
as it would be when the cycle of the alternating undulations are at zero, that is to
say when there is no current flowing. It is with the object of providing such a
rectifier that the cycle of the undulations of the alternating current will be cut at
the zero point and thereby prevent any sparking, which is injurious to the commu-
tator, at the period that the change from the alternating current to the constant
current is being made that my invention is chiefly designed.
A., is the bed plate of the machine, B, the motor provided with the fields, B',
armature, B2, ordinary brushes, B³, and commutator, B. The armature, B2,
secured to the shaft, C, which is journalled in the standards, D, and, D', secured to
the bed plate. The brushes of the motor, B, are connected by the wires, E to, any
suitable electrical current source of, power, which may be either storage battery or
dynamo..
+
F, is an alternating current dynamo, the field, F¹, of which is preferably
laminated as indicated. The fields of the dynamo, F, are sectionally cut, so as to
exhibit the form of the armature. The field magnet cores, F2, are surrounded by
the usual coils, fin this instance there being four coils, which are connected
together in series. The ends of the coils f, are connected to the main alternating
current wires, G.. H, is the armature of the alternating current dynamo, which
consists of two metallic rings H', connected together by four cross bars, H²: · The
rings are supported upon the shaft by the end discs H³, to which the rings are
secured and which are made of insulating material..

page_text: In this instance I show four cross bars, H³, and these correspond to the number
of field magnets.
I, is a core, which is held in position by the lines of force and is preferably made
laminated as indicated and is constructed with recesses, i, extending between the
field magnets across the core. This core is loose on the shaft and maintained in a
stationary position by the lines of force.
J, is a brush suppert which is for the major portion ring-shaped and supported in
an annular groove, d, made in the end of the standard, D. The brush support has
two arms, j, one of which is shown. J₁, is a handle secured to the top of the ring
support, J, K, is the brush holder, which is supported at the outer end of the
spindle, k, which is pivotally held in the arm, j. K', is the carbon brush which has
secured to its outer end the metallic end, l. L. are pins secured in the brush
holder, K, one at each side of the brush. L'. is a cross bar through which the
outer threaded ends of the pin freely extend. 1, are thumb nuts screwed on to the
threaded ends of the pins, L. 12, is a spindle which is secured in the metallic end, !,
of the brush and extends freely through the central part of the cross bar, L.
M, is a spiral spring which surrounds the spindle, 12, and extends between the cross
bar, L, and the end of the brush and is designed to keep the brush, K', which is
preferably made of carbon against the commutator, N. 13, is a conducting wire
leading from the end of the spindle to the brush holder, K.
Although I describe only one brush with the means by which it is supported it
will of course be understood that the other brush is supported in exactly the same
way. O, and, O¹, are the wires leading from the carbon brushes.
The commutator, N, has its inner portion, N', next the shaft made of insulating
material. The central portion, N2, is cylindrical in shape as are also the two end
portions, N3, and, N₁, but the end portions are of reduced diameter. In the central
portion, N, I provide as shown four recesses, n, in which are inserted metallic
sections, ². The end portion N³, I provide with a collar, n³, and the end
portion N, I provide with a collar, n³. The collar, n³, has laterally extending
tongues, n, situated diametrically opposite each other and extending into
recesses, no, in the sections, 1, (see Fig. 2). The collar, n³, has also laterally
extending projections, n, which extend into recesses, n', in the alternate
sections, n. P. is a brush which rests on the collar, n², and is supported in the
pivoted brush holder, P, is a brush which rests on the collar, n³, and is
supported in a pivoted brush holder, pl. 9, and, 9', are the alternating current
wires leading from the main wire, G, to the brushes, P, and, P¹. The alternating
current coming in on the wires, g, and, 9', and the collars, n², and, n³,
respectively is carried out by the brushes, K, and wires, O, and, O', as constant
current.
The alternating current is changed into a constant current through the
commutator, N, constructed as described in the following manner. In order to
provide for the changing of the alternating current into a constant current without
any detrimental effect to or destroying of the commutator it is necessary that the
cycle of undulations of the alternating current must be cut at zero points or during
the period that the current is not flowing. The armature B2, of the motor, B, is
adapted to have a tendency to rotate the shaft at a high rate of speed, in fact at
such a rate as to be slightly in excess as to number of commutations to the
corresponding undulations of the alternating current.
It is therefore necessary to
retard the rotation of the shaft, so that it will, by the commutator at all periods
and under varying conditions of load, change the alternating current entering into
the commutator to a constant current at zero points in the cycle of the undulations
of the alternating current or in other words at the infinitesimal periods at which
no current is flowing. To produce this effect the shaft must be continually and
varyingly retarded in its rotation at all periods when the shaft is rotating at such a
speed as would cause the commutator to change the alternating current into a
constant current at that point in the alternations ahead of the zero point or when
the current is flowing. To effect this and thereby practically prevent any danger

page_text: of sparking and entirely get rid of excessive sparking I provide as hereinbefore
described the armature, H, secured to the shaft and comprising end metallic rings.
and cross conducting bars which thus form a short circuited armature.
As the
The metallic sections of the commutator it will be noticed on reference to Fig. 2,
are set circumferentially behind the position of the corresponding field magnets of
the alternating current dynamo although it may be only very slightly so.
short circuited armature of the dynamo is running in a strong alternating field
a retarding effect is produced upon the conducting bars by the magnets in such field
a little before the magnetism of the magnet falls to the zero point. Consequently a
retarding effect is produced upon the rotation of the armature of the dynamo and
therefore the common shaft is continually and varyingly retarded to suit the
alternations, so that the alternating current is changed into a constant current at
exactly the zero points in the cycle of undulations and sparking of the commutator
is practically prevented.
I show four metallic sections in the commutator to co-act with the brushes, P,
and, P, and, K', K', but it will be understood that the number of sections would
depend on the number of alternations per minute or the speed of driving the shaft
per minute there being of course more sections if the shaft is caused to run slower
and less if such shaft is caused to run at a greater speed.
The size of my rectifier would of course depend upon the volume of current to be
rectified.
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 a rectifier for alternating currents the combination with the shaft driven by
a suitable motor so that it will have a tendency to revolve slightly in excess as to
number of commutations than the number of alternations of the current in the same
time and a commutator suitably formed and secured on the common shaft connected
by brushes to the alternating current wires and having co-acting brushes to lead off
the constant current, of a dynamo having a strong alternating field deriving its
current from the main alternating current wires and having a short circuited
armature secured to the common shaft whereby the rotation of such shaft is
continually and varyingly retarded to bring down the commutations at all periods
into unison with the alternations of the current so that the continuous cycle
of undulations are practically cut at the zero points as and for the purpose
specified.
2. The combination with the shaft driven by an electric motor deriving current
from independent source and having the armature secured on the shaft and
a commutator insulated from the shaft and having an equal number of metallic
sections connected to one brush of the alternating current wire and an equal number
connected to the other brush and two brushes located on sections of different
polarity to carry off the constant current, of a dynamo having the field magnets
connected in series and forming shunt field from the alternating current wires and
an armature having end rings connected together by conducting bars, corresponding
to the number of field magnets, and insulated and supported upon the common
shaft by end discs and an interior core maintained stationary on the shaft, the speed
of the shaft being continually retarded by the short-circuited armature of the
dynamo as and for the purpose specified.
3. The combination with the shaft, the motor, B, having the armature, B³,
secured on the shaft and the commutator insulated from the shaft and provided
with metallic sections in the central portion, end rings having tongues extending
into recesses in the sections diametrically opposite each other, brushes. held in
contact with the end rings and connected by wires to the main alternating current
wires and two carbon brushes located upon sections of opposite polarity and
carrying off the constant current from the commutator, of a dynamo the field
magnets of which derive current from a shunt from the main alternating current

page_text: wires and a short circuited armature comprised of metallic end rings insulated and
supported on the common shaft and connected together by conducting bars, and a
cylindrical core loose on the shaft and having recesses made across it between the
field magnets whereby the lines of force maintain such core from rotating, all the
parts being arranged to co-act as and for the purpose specified.
4. The combination with the commutator of carbon brushes, K¹, each of which is
supported in brush holders, K, and has a metallic end, 1, with an outwardly
extending spindle, 7, pins extending outwardly from the brush holder K; a cross
bar through which the pins and spindle pass, thumb nuts on the threaded ends of
the pins and a spiral spring located between the end of the brush and the cross bar
as and for the purpose specified.
5. The combination with the commutator and brushes each of which is held in a
suitable brush holder, of a continuous flexible conductor leading from the brush to
the holder as and for the purpose specified.
6. The combination with the commutator and brushes each of which is supported
in brush holders as specified, of means situated directly behind the brush and
between it and portion of the brush holder, to flexibly hold the brush against the
commutator as and for the purpose specified.
Dated this 5th don
L 1005
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicant.