Improvements in Apparatus for Relieving Electrical Circuits from Static Charges of Electricity.
Year: 1891

page_text: Date of Application, 29th Dec., 1891
Complete Specification Left, 5th Sept., 1892-Accepted, 8th Oct., 1892
[Communicated from abroad by THE WESTINGHOUSE ELECTRIC AND MANU-
FACTURING COMPANY, of Pittsburgh, Pennsylvania, United States of
America.
Improvements in Apparatus for Relieving Electrical Circuits from
Static Charges of Electricity.
I, OLIVER IMRAY, of No. 28 Southampton Buildings, Chancery Lane, in the
County of London, Chartered Patent Agent, do hereby declare the nature of this
invention to be as follows:-
This invention relates to means of relieving electrical circuits from excessive
static charges of electricity more especially atmospheric electricity to which such
circuits are liable during thunderstorms, and which often result in destructive
discharges. The invention about to be described applies to those circuits which
serve for transmission of alternating currents from a dynamo electric alternator
machine. These currents, as is well known, are of an undulating character,
increasing in electromotive force from zero up to a maximum, then decreasing
to zero, increasing again to a maximum, then decreasing to zero and so on, there
being a succession of moments of time when alternation of current takes place the
electromotive force then passing the zero point and being practically nil. If at
these moments conduction from the line wire to earth be effected, the line can
relieve itself of static charge without affecting the alternating current which it
serves to transmit. For applying this method of relief, a metal discharge plate
connected to earth is fixed in proximity to the two revolving rings on which
bear the collecting brushes of the alternator, and pairs of metal plates respectively
connected to those rings, are fixed at such points of the circumference that as the
armature revolves each presents itself to the fixed metal plate at the moment when
the current generated by the machine is being alternated and passing the zero point of
electro-motive force. The edges of the plates being serrated, and the air space
between those edges being very narrow, there is a discharge to earth of such static
electricity as may be in the line at the moment when the revolving plate passes
the fixed plate, at which moment the electro motive force of the current generated
by the machine is nil. The discharge plate, which is connected to earth instead of
being arranged in close proximity to the revolving plates so as to take discharge
through an air space, may be in the form of a brush or rubber actually bearing on
the revolving discharge plates, which in this case would be fixed like segments of
a commutator. Instead of a single fixed discharge plate or rubber there may be
several of these arranged to discharge at several of the alternations of current
which take place during each revolution of the armature.
Dated this 29th day of December 1891.
ABEL & IMRAY,
Agents for the Applicant.

page_text: COMPLETE SPECIFICATION.
Improvements in Apparatus for Relieving Electrical Circuits from
Static Charges of Electricity.
I, OLIVER IMRAY, of No. 28, Southampton Buildings, Chancery Lane, in the
County of London, 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 :-
My invention relates to means of relieving electrical circuits transmitting
alternating currents from excessive static charges of electricity more especially
atmospheric electricity to which such circuits are liable during thunderstorms, and
which often result in destructive discharges. Alternating currents, such as are
produced from a dynamo electric alternator machine, are as is well known, of an
undulating character, having varying electromotive force such as may be represented
by the diagram Fig. 1 of the accompanying drawings; that is to say, taking the
straight line g to be the zero line, the electromotive force decreases from a -
maximum as indicated by the f branch of the wave curve, to zero, then increases to
a maximum, again decreases to zero, then increases again to a - maximum and
so on, the electromotive force being nil at each alternation of current that is at
each moment when the wave curve crosses the zero line either ascending or
descending. I take advantage of these characteristics of the alternating current
to effect relief of the circuit from such static charge as it may have, by permitting
conduction from the line to earth at one or more of the moments when alternation
of the current takes place, and when the electromotive force of the current generated
by the machine is nil, so that this current is not affected by the momentary con-
nection of the line to earth. This principle may be applied to alternator machines
in various ways.
One arrangement is shewn in Fig. 2 of the accompanying
drawings which is a side view of one bearing A and part of the armature shaft B of
an alternator dynamo electric machine. On the shaft B are fixed as usual the two
metal circuit rings cc on which bear the collectors or brushes bb connected to
the circuit leads P. Between the rings I fix a ring C of insulating material
having projecting from it several serrated metal plates which are in electrical
connection with the ring c¹ and several such plates e connected to the ring c².
Supported from the bearing A by an arm K or otherwise I fix a serrated metal
plate E electrically connected by wire e to earth G.
This plate E is adjusted so as to present its serrated edge in close proximity to
the serrated edges of the plates el e as they revolve past it and in such position
relatively to those plates that they pass it at moments of alternation of current.
At any of these moments static electricity in the line can discharge itself to earth
across the narrow air space between the plate E and the plate e¹ or e³ then passing
it, without affecting the current generated by the machine the electromotive force
of which is then nil.
There may be several plates like E such as E¹ arranged around the armature
shaft each in such a position as to afford conduction from the plates ee only at
moments of alternation of current.
Instead of effecting discharge of the static electricity through an air space as
between two plates E and e¹ or e² having their edges in close proximity, it may be
effected by actual contact as shewn in the side view Fig. 3 and transverse section
Fig. 4.
In this modification the insulating ring C has let into it in the manner of commutator
segments plates ee electrically connected respectively to the rings c¹ c³, and a
brush or collector E' connected by wire e to earth G is arranged to bear on the
ring C making contact with the plates ee as they pass under it. The brush E' is
BO adjusted that, these contacts are made at the moments when alternation of the

page_text: machine current takes place, and when therefore the electromotive force of the
current is nil.
Although I have described the apparatus according to this invention applied to
a dynamo electric generator, obviously the circuit of an electromotor or other
machine moving in concert with the alternations of the current can be relieved of
static charges by the same means. Also when the current is of an intermittent
instead of an alternating character, the circuit may be in like manner relieved of
static charges, the relief in this case as in that of an alternating current being
effected at the moments when the electro-motive forces of the current is nil or at
minimum.
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 :-
In combination with an electric circuit for an alternating or intermittent current
and a machine moving in concert with the alternations or intermissions, a conducting
plate or brush connected to earth and fixed in close proximity to or in contact with
plates so arranged on the machine that static electricity in the circuit can discharge
itself to earth at moments of nil or minimum electromotive force, substantially as
described.
1
11000
ABEL & IMRAY,
Agents for the Applicant.