Improvements in Electric Arc Lamps.
Year: 1899

page_text: Date of Application, 22nd Nov., 1899-Accepted, 30th Dec., 1899
COMPLETE SPECIFICATION.
Improvements in Electric Arc Lamps.
We, THE BRITISH THOMSON-HOUSTON COMPANY, LIMITED, of 83, Cannon Street,
in the City of London, Electrical Engineers, do hereby declare the nature of
our said invention (which has been communicated to us from abroad by Edwin
W. Rice, Jr., residing at Schenectady, in the County of Schenectady, State of
New York, United States of America, Electrical Engineer) and in what manner
the same is to be performed, to be particularly described and ascertained in and
by the following statement:-
The object of the present invention is to provide an alternating current arc
lamp which will burn with a comparatively steady are under currents of low
frequency and through the instrumentality of a single arc-regulating electrode.
In carrying out the invention we provide the lamp with a plurality of elec-
trodes carrying polyphase currents, one of said electrodes being under the
influence of the arc regulating mechanism of the lamp to maintain a uniform
arc length. When operating with a two-phase current we provide a lamp with
three electrodes, two of which connect with two of the leads from a two-phase
circuit, and the other from a common return for the two phases, the latter being
controlled by the arc regulating circuit. When operating with a three-phase
current, we employ four electrodes, three of which connect with respective leads
of the tri-phase circuit, and the other with a compensating wire symmetrically
related with respect to the three phases, and on which at the point of connection
with the tri-phase system there is zero potential. In the lead between the
movable electrode and this compensating wire may be interposed regulating
circuits which adjust the position of the movable electrode. With an organiza-
tion of this kind some one of the phases is always active in maintaining the arc,
as there are no intervals of zero potential at the arc terminals, and a steady
light is produced at a much lower frequency than is possible with a single-phase
current. This will be readily understood on consideration of the fact that the
energy of a polyphase system is substantially constant from instant to instant.
The several features of novelty of the invention will be hereinafter more par-
ticularly described, and will be definitely pointed out in the claims.
In the drawings, which illustrate our invention, Fig. 1 is a view of a two-
phase lamp embodying our improvements, an enclosed-arc type of lamp being
shown; Figs. 2 and 3 are diagrammatic views of the controlling circuits of a
two and a three phase lamp respectively.
While we have herein illustrated a two-phase and three-phase type of lamp,
we wish it to be understood that our invention is equally applicable to a poly-
phase current of any number of phases, and have specifically shown the two
types, merely as examples for systems commonly employed in the commercial
distribution of electricity.
Referring first to Fig. 2, 1, 2, 3 represent three carbon electrodes, the former
of which connect respectively with two leads 4, 5, of a quarter phase distribu-
tion circuit. A third carbon connects through a regulating coil of the lamp 5*

page_text: with a common return wire 6. If the system be of the type however in which
two independent quarter phase circuits are employed, the third carbon may have
a common connection with two of the leads, of may be fed by a-transformer the
secondary of which is provided with. three leads, as indicated in the figure. The
regulating mechanism is shown only in a diagrammatic way in the drawing,
as of course many different feed-regulating devices and circuit arrangements
may be employed. The coil 5" being in series with the arc and electrically con-
nected with the movable electrode, varies in its magnetic effect under the varying
lengths of the arc and may operate a clutch in the usual manner for effecting
periodic feed of the movable electrode. The movable electrode should be given
a greater cross-section than the electrodes 1 and 2, since it carries the sum of
the currents transmitted through the lower carbons. We have shown the arc as
surrounded by a transparent or translucent enclosure 7, to prolong the life of the
electrodes; this however is not essential to the practice of our invention, as
the latter may be applied to open air as well as enclosed arcs. It will be evident
that since the two currents differ in phase, the arc will be much steadier with
low frequency than where a single phase current is employed since there will
always be a considerable potential difference between the arc terminals.
With a tri-phase current still better results may be obtained. In this case we
prefer to connect the movable electrode and regulating coil with a point of zero
potential between the three supply-wires of the triphase circuit. An organiza-
tion of this kind is depicted in Fig. 3, where 8, 9 and 10 represent the three
leads of a
tri-phase circuit, and 11 a source of tri-phase curent which may be a
supply generator located at the main station; or a local source, such as a trans-
former. The movable electrode 12 and series regulating coil 13 are connected
with a point 14 common to the three phases by a compensating wire 15. At the
point 14, as is well understood, there is zero potential so long as the circuit is
uniformly balanced, but between the movable electrode 12 and the three fixed
electrodes 16, 17, 18, connecting respectively with the leads 8, 9 and 10, there
is a potential varying in value from zero to the maximum potential of the system.
The regulating coil 13 will therefore be energized and will strike the arc in a
manner similar to the ordinary operation of any arc lamp, and an arc will be
maintained between the movable electrode and each of the three stationary
electrodes. As the sum of the three currents is a constant value, the luminosity
of the arc will be fairly constant at very low frequencies. The stationary
electrodes should be spaced a wider distance apart relatively to one another
than the arc length for which the lamp is adjusted as it is undesirable to permit
an arc across them which might be maintained after the fashion of a Jablochkoff
candle by the path between the different potential mains if the distance were
sufficiently short to maintain an arc and would conduce to an irregular action of
the lamp.
Having now particularly described and ascertained the nature of our said
invention (as communicated to us from abroad) and in what manner the same is
to be performed, we declare that what we claim is:-
1. An arc lamp provided with a plurality of stationary electrodes adapted for
connection with currents differing in phase, a single movable electrode, and a
regulator controlling said electrode to adjust and maintain the arc.
2. A multiphase arc lamp with a plurality of electrodes in circuit with two or
more currents differing in phase, a movable electrode in a common retun for said
currents, and a regulating device for maintaining and adjusting the arc.
3. A triphase arc lamp, comprising three electrodes adapted for connection
with the three leads of a triphase circuit, a fourth electrode connecting with a
point common to the three phases, and means for feeding the electrodes rela-
tively to one another, to maintain the arc constant.
4. A triphase arc lamp provided with three electrodes connecting respectively
with the three leads of a triphase circuit, a fourth electrode connected to a point

page_text: of zero potential with respect to said circuit, and a regulating coil between said
electrode and point of zero potential.
5. A triphase are lamp provided with three electrodes connecting respectively
with the three leads of a triphase circuit, a fourth electrode connected to a point
symmetrically related electrically to said leads, and means for regulating the arc.
6. An arc lamp provided with a plurality of electrodes symmetrically related
electrically with respect to the leads of a polyphase alternating current circuit
and means for effecting relative movement between one of the electrodes and the
others to maintain the arc.
THE BRITISH THOMSON-HOUSTON Co. LTD.
ALFRED CLEMENTS,
Assistant Secretary.
GEORGE FRANKLIN,
Directors.
W. MARTINDALE,