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Патент USA US2117993

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May 17, 1938.
D. G. PRINZ
2,1 17,993
ELECTRINC DISCHARGE DEVICE
Filed June 29‘, 1937
IIVYENTWR.
Patented May 17, 1938
, 2,111,993
' UNITED ‘STATES
PATENT OFFICE
2,117,993
ELECTRIC DISCHARGE DEVICE
Dietrich Giinther Prinz, Wembley, Middlesex,
England, assignor to The General Electric
Company. Limited, London, England, a company
of Great Britain
' Application June 29, 1937, Serial No. 150,897
In Great Britain July 3, 1936
8 Claims. (Cl. 175—354)
This invention relates to‘means for operating
electric discharge devices, such as mercury va
by this voltage until the main discharge is es
_ tablished.
por devices, of the type having a cathode from
which vapor is generated during operation, from
Certain embodiments of the invention will
now be describedL by way of example, ‘with ref-'
an approximately sinusoidal A. C. supply, so that ' erence to the accompanying drawing. Of these,
the‘ arc, which has to be started in each cycle, Figures 1, 2 and 3 show, by way of example, var
can be started at a controlled point in the cycle. ious circuits for the production of the ignition
It has been proposed to start an arc to the peak voltage and for the supply of voltage to
mercury cathode of a mercury arc device by ap
the auxiliary electrode.
plication of high voltage to an inner auxiliary
electrode. This involves, however, either incon
veniently high voltages or frequencies or vapor
by way of‘ example, some arrangements‘ and 10
shapes of the auxiliary electrode.
In Figure 1, the discharge device consists of
a glass envelope I, containing a mercury pool
pressure, or special arrangements, such as aux
iliary hot cathodes.
Figures 4 and 5 show, ’
2 with a cathode lead 3, an anode 4 and an inner
It has been proposed also to start an are by
means of an external ignition electrode, for in
‘auxiliary electrode 5. - This electrode 5 may con
15
sist of a simple wire. sealed throughthe glass
stance, a metal foil, ?xed on the' glass wall near wall,‘ or of a ring (as shown), or it maybe of
the mercury surface. In this case, a cathode spot _ any other suitable shape, of which examples are
is very easily formed on the edge of the mercury given in the modi?cations later described.
probably due to the abnormally high electrical
'The external electrode 6 may consist of a wire
?eld arising at this sharp edge.
'
'
or other metal body, touching the glass near the
This method of ignition, however, has some
considerable disadvantages.
Since the main anode circuit always contains
a certain self inductance, theanode current will
increase, not suddenly, but at a '?nite rate. On
the other hand, a minimum current of about 1 '
' or 2 amps. is required for maintaining the oath
0
mercury edge, but preferably of a metal foil '
?xed on the glass and surrounding the whole
mercury pool.
'
_
Both the auxiliary electrode 5 and the exter
5
nal electrode 6 are connected with one terminal
of the high voltage winding of a transformer l,.
the other terminal of the said high voltage wind
ing being connected with the cathode lead 3. ‘In
the connection between the electrode 5 and the
ode spot. Therefore, since the duration of the
spot is very short, the spot may be extinguished
before‘ a current sufiicient to maintain it de
said winding, there may be inserted a resistance '
velops.
I‘, if desired.
’
7
>
Another disadvantage of forming a cathode
The primary winding of the transformer 1 is
spot solely by means of an external electrode is connected with the A. C. source 8 through a re
that, if the anode be placed far from the cathode sistance 9 and a gridglow tube In, the grid of
(for‘instance, to protect it against evaporated or which is connected with its cathode, through
sputtered mercury), the main discharge may not, the secondary winding of a transformer II
be able to start from the cathode spot to the main (which is preferably a peak transformer of the
anode, owing, for example to negative charges
40 formed on the glass walls or other'insulators be
tween cathode and anode.
, . The object of the present invention is to pro
vide means for starting the discharge free from
the disadvantages of either of these two methods.
According to the invention, means for the pur
pose speci?ed comprise as part of the said elec
tric discharge device, both an external electrode
near the cathode and an internal auxiliary elec
trode, impulsive means for applying to the said
external electrode an impulsive voltage, where
by a cathode spot is formed, and maintaining
means for applying to the said internal auxiliary
electrode a voltage of such magnitude, sign and
56 duration that the cathode spot is maintained
saturated iron core type) and a D. C. source It‘.
The primary winding of the transformer ll , 40
is fed by an A. C. source ll of the same fre—
quency as the A. C. source 8 and as the, supply
to the main circuit. This main'circuit is shown
in Figure 1 as an A. C. source _a connected
through a transformer b with the electrodes 3
and l of the discharge devicel in series with a
D. C. load c.
The main circuit need not be as
shown in Figure 1, but may be of any kind usual
with vapour electric devices of the type speci?ed.
The secondary voltage of the transformer II,
in cooperation with the D. C. source l2, ren
ders the grid glow tube It) conductive, in known
manner, at a definite moment of each cycle, so
that an impulsive current then flows through
the primary of the transformer 1. This impul
65
2,117,998
2
sive current produces a high voltage on the sec
ondary of the transformer ‘I, so‘ that the exter
nal electrode 6 forms a cathode spot on the edge
of the mercury pool.
BI
At the same moment, ‘a
discharge is started between this cathode spot
and the inner auxiliary electrode 5; this dis
charge is maintained for a ?nite time by the‘
magnetic energy stored in the transformer ‘I.
If the transformer be suitably designed, this en
10 ergy will be great enough to -maintain the dis
charge to the electrode 5, until the main dis
charge to the anode 4 is established.
The A. C. sources 8 and I3, or the A. C. source
I3 only, may be provided with phase shifting
15 devices of known kind, so that the moment of
ignition in each cycle may be varied in a man
ner well known in connection with all grid con
trolled converters and thus the mean current
tween the external electrode 6” andthe cathode
3"; its peak then must be made sharp enough
and high enough to produce a cathode spot on
the mercury. But preferably, as ‘shown 'in the
?gure, the voltage on the external electrode 6” is
made to rise still more sharply by inserting a
spark gap I8 between the secondary winding of
the transformer ‘I" and the electrode 6"‘. The
spark gap I8” may consist of a point separated
from a plate by a distance such that only the‘ 10
positive voltage peaks can break down the gap
and reach the electrode Ii". In this case, a re
sistance I9" may be provided to remove the elec
trical charges from the electrode 6" in the inter
val between the peaks.
15
The means for applying a voltage to the auxil
iary electrode 5’ which are shown in Figure 2 by
the numerals I4'—I'I’ may be used in the are
rangement shown in Figure 1 in substitution for
varied.
20
Figure 2 shows another example of a circuit the connection of the electrode 5 through the re
20
according to the invention. Reference numerals ' sistance I4 with the secondary winding of trans
I’—8’ have the same meaning as I-B, in Figure 1. former ‘I.
The peak voltages of the A. C. source 8' ‘cause
As mentioned above, it may be sufficient some- .
sparks to pass across the spark gap 9’, thus charg
25 ing the condenser I0’ and causing a heavy current
impulse to flow through the primary winding of
the transformer ‘I’; a voltage peak therefore oc
ours in the secondary winding of this transformer
and a cathode spot is formed by the external
times to form the auxiliary electrode as a simple
wire sealed through the glass wall; in other cases, 25
it is preferable to give it a form that enables it to '
perform other functions as well.
30 electrode 6 as described above.
tering from the cathode spot. In this ?gure, the
glass envelope 2| contains an anode 22, sealed
and supported at 23, and an auxiliary electrode
24, sealed into and‘ supported by a foot-tube and
pinch 25. The annular depression formed by 35
sealing the foot-tube to the glass envelope is
?lled with mercury 28, for which a leading-in wire
21 is provided. The annular form of the mercury
pool has the advantage of increasing the length
It may be pointed out that two sparks occur in
each cycle, thus producing one positive and one
negative voltage peak on the external electrode
6'. Only the positive peak is used to form the
35 spot. By inserting a second transformer in the
circuit ‘I’, 8’, 9’, III’, the second spark may be
used for forming another positive voltage peak,
so that another dischargedevice may be ignited
alternately with the device I’. This arrangement
40 may be useful in known symmetrical recti?er cir
In Figure 4, for example, the auxiliary elec
trode is formed as a baf?e or screen protecting
the anode from the vapour stream and the sput
of the mercury edge for a given amount of mer
30
40
cury; a metal foil forming the external electrode
cuits, fed by 2-phase, 6-phase or 12-phase sup
can be applied not only on the outer side 28, but
plies. If the A. C. source 8' be provided with a ' also
on the inner side 29 of this-mercury pool.
phase shifting device, ‘only one such device is
Furthermore, its presence on this inner side
required for each pair of recti?ers.
makes it easy to cool the mercury (for example
In Figure 2, a D. C. source I4’ is connected
by a blast of air); cooling is known to promote
through a resistance IS’ with a condenser I6’,
formation of cathode spots.
'
this condenser in turn being connected with the theThe
diameter of the auxiliary electrode 24 is
auxiliary electrode 5’ through an impedance I1’.
As soon as the cathode spot is formed by the greater than that of the anode 22 and that of the
mercury pool 26, so that the‘anode is protected 50
external electrode 6’, a discharge takes place be
tween the mercury cathode 2’ and the auxiliary from the vapour stream produced by the cathode
spot as well as from any sputtered mercury.
electrode 5’, the duration of said discharge de
In Figure 5, another shape of the auxiliary
pending on the values of the condenser I6’, the electrode is shown. In this ?gure, the glass vessel
‘resistance I5’, the impedance I1’ and the voltage
of the D. C. source I4’.
If these values be chosen
30 contains in aside arm 3| an anode 32 sup
ported by a rod 33 sealed in at 34, the said rod
suitably, the auxiliary discharge will be main
being protected by a quartz sheath 35 held in
tained until the main discharge has been estab
vposition by washers 36 and a spring 31. 38 is
lished.
mercury pool, and 39 is the cathode lead.
In the succeeding non-conductive part of the the
The auxiliary electrode 40,'supported on a lead 60
60 cycle, the condenser I6’ is recharged by the D. C.
sealed in at 42, is formed as a grid surrounding
source I4’ through the resistance I5’. This re
the anode 32. This arrangement facilitates the
sistance must be high enough to prevent a con
tinuous arc discharge taking place between the starting of the discharge between the cathode and
anode; and, if the discharge tube be used as a
auxiliary electrode 5’ and the cathode.
The impedance I'I’ need not be a pure ohmic recti?er, it also decreases the risk of back ?ring
during the inverse half cycle. When using a cir
resistance; it may be replaced by a self induct
cuit according to Figure 1>or 2, the potential of
ance; indeed it has been found that in this way
a more uniform duration of the auxiliary dis
charge can be obtained.
In Figure 3, the reference numerals I"-8”
and I4"-—I'I” have the same meaning as I'--8’
and I4’-I'I’ in Figure 2; but the transformer 'I"
is a peak transformer of the saturated iron core
type, producing an impulsive voltage. Its sec
ondary winding may be connected directly be
the auxiliary electrode never differs very greatly
from that of the cathode during the inverse
period; the electric ?eld tending to produce a 70
reverse discharge is con?ned to the space between
the anode and auxiliary electrode. On the other
hand, a back discharge between the anode-and
the auxiliary electrode is improbable because
these electrodes are near together and, in the cir
2,117,993
cult according to Figure 1, because of the resist
3
vided by a transformer the secondary of which
is arranged to supply a unidirectional impulse
ance of the transformer windings and the addi
tional resistance ll inserted in the lead to the . current derived from an alternating‘current of
auxiliary electrode 5.
I claim:
1. In a mercury vapor discharge device, a tube
having an anode and a cathode, the cathode com
prising a pool of mercury from which vapor is '
generated during operation, a main circuit carry
10 ‘lng alternating current of known frequency con
nected for discharge between the anode and
cathode of said tube, said main circuit including
a direct current load, an external electrode ar
ranged to cooperate with the mercury pool of
the cathode in the formation thereon of a oath.
ode spot, a circuit between said external elec
trode and the cathode carrying an impulse cur
rent for establishing a positive potential on the
external electrode during each cycle of the al
ternating current in the main circuit for form
ing the cathode spot on the mercury pool, an
auxiliary electrode mounted within the tube be
tween the anode and cathode for cooperation
5. The mercury vapor discharge device as in
claim 1 wherein the impulse current for forming
the cathode spot on the mercury pool is provided
by the secondary of a saturated core transformer
the primary-of which is supplied with impulse
current of proper frequency from an alternating
current source with a‘ condenser and‘ spark dis
charge in circuit.
6. The mercury vapor discharge device as in
claim 1 wherein the impulse current for forming
the cathode spot on the mercury pool is pro
vided by the secondary circuit of a saturated core
transformer which circuit includes a undirec-'
tional spark discharge, the primary of the trans
former being supplied from an alternating cur
rent of proper frequency.
‘
with the cathode spot, and circuit means ar
ranged to provide an impulse current for dis
7. The mercury vapor discharge device as in
claim 1 wherein the impulse current for the dis 25
charge between said auxiliary electrode and the
cathode spot for maintaining, the cathode spot
until the main circuit discharge is established.
charge between the auxiliary electrode and the
cathode spot is provided by a condenser arranged
2. The mercury vapor discharge device as in
30 claim 1 wherein the current for providing the im
pulse discharge between the auxiliary electrode
and the cathode spot is derived from the cir
, cult which is arranged to form said cathode spot
on the mercury pool.
3. The mercury vapor discharge device as in
claim 1 wherein the impulse current for form
ing the cathode spot on the mercury pool is pro
vided by the secondary of a transformer the pri
mary of which is supplied with unidirectional
40
proper frequency and the impulse current for the
discharge between the auxiliary electrode and the
cathode spot is provided by a branch circuit
from the secondary of said transformer.
impulse current produced by passing an alternat
ing current of proper frequency through a glow
tube recti?er.
4. The mercury vapor discharge device as in
claim 1 wherein the impulse current for forming
45 the cathode spot on the mercury pool is pro
to be charged from a direct current source and
to be discharged between the auxiliary electrode
and the cathode spot with the formation of the 30
cathode spot.
-
8. The mercury vapor discharge device as in
claim 1 wherein the impulse current for forming
the cathode spot on the mercury pool is provided
by a transformer the secondary of which is ar 35
ranged to supply a unidirectional impulse cur
rent produced from an alternating current of
proper frequency and the impulse current for the
discharge between the auxiliary electrode and the
cathode spot is provided by'a condenser arranged 40
to be charged from a direct current source and
to be discharged between the auxiliary electrode
and the cathode spot with the formation of the
cathode spot.
__
-
DIETRICH GUNTHER PRINZ.
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